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1. Tro CHEMISTRY; A Molecular Approach Chapter 1
Matter, Measurement, and Problem Solving
2. Tro, Chemistry: A Molecular Approach - Chap 1 2 Chemistry in Our World Cosmetics
Fuels
Pollution
Food/Additives
Metals/Corrosion
Chemistry affects our everyday life in ways that you probably never imagined.
How many people drove to school this morning?
Do you put gasoline in you car? Without the chemical reaction called combustion you would still be driving a horse and buggy.
How many people walked up the sidewalk?
Did you know that cement or concrete is formed from a chemical reaction of compounds formed from limestone, chalk, and clay, with water.
Chemistry affects our everyday life in ways that you probably never imagined.
How many people drove to school this morning?
Do you put gasoline in you car? Without the chemical reaction called combustion you would still be driving a horse and buggy.
How many people walked up the sidewalk?
Did you know that cement or concrete is formed from a chemical reaction of compounds formed from limestone, chalk, and clay, with water.
3. Tro, Chemistry: A Molecular Approach - Chap 1 3 Question Over 25 million chemicals are known.
Can you list some examples? Sources and uses?
Write down the common student responses along with the student names.
Alcohol, Salt (2006)Write down the common student responses along with the student names.
Alcohol, Salt (2006)
4. Tro, Chemistry: A Molecular Approach - Chap 1 4 Types of Chemicals Natural
Plant sources
Animal Sources
Mineral Sources
Synthetic
Medicines
Plastics
Fibers Where do chemicals come from?
You may be surprised to find that chemicals can come from many places.
They may come from plant sources; in fact in early times, a chemical precursor to aspirin came from extracts of willow trees. Many modern day chemicals are isolated from plants or animals.
Some chemicals come from mineral sources. Rock salt is mined from huge underground reserves for use in the winter. Many other minerals are mined for use as is, or sometimes refined and chemically reacted to provide other chemicals for everyday use.
How many girls in here are wearing lipstick?
The Lipstick that you are wearing may contain Bismuth oxychloride, which is synthetic pearl, which helps to imparts a frost or shine to your lipstick.
Bismuth is the by-product of lead and copper refining, as well as other metals to a smaller degree. Bismuth occurs very rarely in nature. It is on the periodic table of elements under the symbol Bi at atomic number 83. It is very heavy and chemically resembles arsenic and antimony. It has a whitish/iridescent hue and has a very high shine property to it. Of all the heavy metals it is the only non-toxic. Bimsuth is a carrier for fuel in nuclear reactors. Bismuth components are used in everything from detection work, to making acrylic fibers, to safety devices in fire detection and extinguishing items, soldering, magnets and medicine as well as cosmetics. Because it is a by-product of lead refining, bismuth oxychloride should be lead free when companies begin using it in their cosmetics.
Source: http://ezinearticles.com/?Mineral-Makeup-and-Bismuth-Oxychloride&id=68978Where do chemicals come from?
You may be surprised to find that chemicals can come from many places.
They may come from plant sources; in fact in early times, a chemical precursor to aspirin came from extracts of willow trees. Many modern day chemicals are isolated from plants or animals.
Some chemicals come from mineral sources. Rock salt is mined from huge underground reserves for use in the winter. Many other minerals are mined for use as is, or sometimes refined and chemically reacted to provide other chemicals for everyday use.
How many girls in here are wearing lipstick?
The Lipstick that you are wearing may contain Bismuth oxychloride, which is synthetic pearl, which helps to imparts a frost or shine to your lipstick.
Bismuth is the by-product of lead and copper refining, as well as other metals to a smaller degree. Bismuth occurs very rarely in nature. It is on the periodic table of elements under the symbol Bi at atomic number 83. It is very heavy and chemically resembles arsenic and antimony. It has a whitish/iridescent hue and has a very high shine property to it. Of all the heavy metals it is the only non-toxic. Bimsuth is a carrier for fuel in nuclear reactors. Bismuth components are used in everything from detection work, to making acrylic fibers, to safety devices in fire detection and extinguishing items, soldering, magnets and medicine as well as cosmetics. Because it is a by-product of lead refining, bismuth oxychloride should be lead free when companies begin using it in their cosmetics.
Source: http://ezinearticles.com/?Mineral-Makeup-and-Bismuth-Oxychloride&id=68978
5. Tro, Chemistry: A Molecular Approach - Chap 1 5 Chemistry The branch of science that deals with the characteristics, properties, composition, and reactions of all materials.
What do we mean by “reaction”?
Iron reacts with oxygen to form rust:
4Fe(s) + 3O2(g) 2Fe2O3(s)
solid/metal gas red solid Chemistry deals with the propertied of materials and the changes materials undergo.
When a chemical change occurs we say that a reaction has taken place.
The chemical or chemicals involved have somehow changed their chemical composition.
Here is an example. The iron of this nail is rusting (or undergoing a chemical reaction) to form iron oxide
http://www.dit.ie/DIT/science/chemistry/rsccomp/competition01/hawkesclancy/garage/rust.html
Rust
Chemistry deals with the propertied of materials and the changes materials undergo.
When a chemical change occurs we say that a reaction has taken place.
The chemical or chemicals involved have somehow changed their chemical composition.
Here is an example. The iron of this nail is rusting (or undergoing a chemical reaction) to form iron oxide
http://www.dit.ie/DIT/science/chemistry/rsccomp/competition01/hawkesclancy/garage/rust.html
Rust
6. Tro, Chemistry: A Molecular Approach - Chap 1 6 Chemistry is Important Economically 25 million chemicals known.
5 million chemicals discovered each year.
Chemical industry is fifth largest in the US.
US sales over $550 billion.
1 million people are employed.
In 2005, US produced 36,520,000 metric tons of Sulfuric Acid. I think that I may have impressed upon you the importance of chemistry, but here are some more facts that may interest you further.
Chemical and Engineering News 2005. I think that I may have impressed upon you the importance of chemistry, but here are some more facts that may interest you further.
Chemical and Engineering News 2005.
7. Tro, Chemistry: A Molecular Approach - Chap 1 7 Discuss Do you believe this statement?
Can you think of any exceptions?
Does this surprise you?Do you believe this statement?
Can you think of any exceptions?
Does this surprise you?
8. Tro, Chemistry: A Molecular Approach - Chap 1 8 Structure Determines Properties the properties of matter are determined by the atoms and molecules that compose it
9. Tro, Chemistry: A Molecular Approach - Chap 1 9 Atoms and Molecules atoms
are submicroscopic particles
are the fundamental building blocks of all matter
molecules
two or more atoms attached together
attachments are called bonds
attachments come in different strengths
molecules come in different shapes and patterns
Chemistry is the science that seeks to understand the behavior of matter by studying the behavior of atoms and molecules
10. Tro, Chemistry: A Molecular Approach - Chap 1 10 The Scientific Approach to Knowledge philosophers try to understand the universe by reasoning and thinking about “ideal” behavior
scientists try to understand the universe through empirical knowledge gained through observation and experiment One of the goals of scientists is to solve problems. For chemists we want to solve chemical problems.
There is a specific method that we use to approach problem solving.
It is called the scientific method.
It is a systematic approach to research.
First you must carefully define the problem.
Next you perform experiments, make observations, record information or DATA.
Then you analyze the data, you form an idea (a hypothesis) that explains the data and observations.
Then you repeat the process. You use a new plan or conduct new experiments to determine if your hypothesis is sound
Over time, a hypothesis that becomes widely accepted is called a theory or a law. These are concise statements that explain the relationship between observed phenomena that are always the same under given conditions. Laws are usually given in terms of a mathematical definition.
One of the goals of scientists is to solve problems. For chemists we want to solve chemical problems.
There is a specific method that we use to approach problem solving.
It is called the scientific method.
It is a systematic approach to research.
First you must carefully define the problem.
Next you perform experiments, make observations, record information or DATA.
Then you analyze the data, you form an idea (a hypothesis) that explains the data and observations.
Then you repeat the process. You use a new plan or conduct new experiments to determine if your hypothesis is sound
Over time, a hypothesis that becomes widely accepted is called a theory or a law. These are concise statements that explain the relationship between observed phenomena that are always the same under given conditions. Laws are usually given in terms of a mathematical definition.
11. Tro, Chemistry: A Molecular Approach - Chap 1 11 From Observation to Understanding Hypothesis – a tentative interpretation or explanation for an observation
falsifiable – confirmed or refuted by other observations
tested by experiments – validated or invalidated
when similar observations are consistently made, it can lead to a Scientific Law
a statement of a behavior that is always observed
summarizes past observations and predicts future ones
Law of Conservation of Mass This process of experimentation to describe nature is called the scientific method.
It always follows the same form.
An observation in made, you come up with an explanation, then you test to see if your explanation holds water.
repeat the process.
A hypothesis is a proposal about an observation. You have to provide experiments to test you hypothesis.
A theory is a well-established hypothesis. It is well accepted. It usually is still under consideration and scientists are planning experiments to continue to test the theory.
This process of experimentation to describe nature is called the scientific method.
It always follows the same form.
An observation in made, you come up with an explanation, then you test to see if your explanation holds water.
repeat the process.
A hypothesis is a proposal about an observation. You have to provide experiments to test you hypothesis.
A theory is a well-established hypothesis. It is well accepted. It usually is still under consideration and scientists are planning experiments to continue to test the theory.
12. Tro, Chemistry: A Molecular Approach - Chap 1 12 From Specific to General Understanding a hypothesis is a potential explanation for a single or small number of observations
a theory is a general explanation for the manifestation and behavior of all nature
models
pinnacle of scientific knowledge
validated or invalidated by experiment and observation This overhead helps to define some of these terms associated with the scientific method.
An experiment is controlled research. The idea of controlling the variables in the experiment is very important.
A law is a concise statement that summarize the behavior of nature and has no exceptions. These are hypotheses that have been around for a long time and have gained universal acceptance.
This overhead helps to define some of these terms associated with the scientific method.
An experiment is controlled research. The idea of controlling the variables in the experiment is very important.
A law is a concise statement that summarize the behavior of nature and has no exceptions. These are hypotheses that have been around for a long time and have gained universal acceptance.
13. Tro, Chemistry: A Molecular Approach - Chap 1 13 Scientific Method Another way to visualize the scientific method.
Notice the flow from one step to another. Usually this process is repeated by many, many chemists before the process is ever called complete. And in truth the steps are never finished. An experiment conducted tomorrow may show that one of our trusted and beloved laws may have exceptions, and then the process would start all over again.
Another way to visualize the scientific method.
Notice the flow from one step to another. Usually this process is repeated by many, many chemists before the process is ever called complete. And in truth the steps are never finished. An experiment conducted tomorrow may show that one of our trusted and beloved laws may have exceptions, and then the process would start all over again.
14. Tro, Chemistry: A Molecular Approach - Chap 1 14 Which Beaker is Empty? Which glass is empty!
Right! Neither one is empty.Which glass is empty!
Right! Neither one is empty.
15. Tro, Chemistry: A Molecular Approach - Chap 1 15 Classification of Matter matter is anything that has mass and occupies space
we can classify matter based on whether it’s solid, liquid, or gas Everything is made up of matter. By definition all matter has mass and takes up space.
Chemistry is the branch of science that is concerned with matter. How it behaves and what reactions it undergoes.
The Mass of an object measures how much matter is present.
(Get a demo, use a mass from the physics lab, 1 kilogram would work nicely)
Don’t get mass confused with weight. Weight is a measure of how strongly an object is attracted to the earth. A 1 kilogram object has a weight of 2.2 pounds on earth, but weighs much less on the moon. (Approximately 1/6th the weight.)
Everything is made up of matter. By definition all matter has mass and takes up space.
Chemistry is the branch of science that is concerned with matter. How it behaves and what reactions it undergoes.
The Mass of an object measures how much matter is present.
(Get a demo, use a mass from the physics lab, 1 kilogram would work nicely)
Don’t get mass confused with weight. Weight is a measure of how strongly an object is attracted to the earth. A 1 kilogram object has a weight of 2.2 pounds on earth, but weighs much less on the moon. (Approximately 1/6th the weight.)
16. Tro, Chemistry: A Molecular Approach - Chap 1 16 Classifying Matter by Physical State matter can be classified as solid, liquid, or gas based on the characteristics it exhibits This table summarizes some of the properties of solids liquids and gasses.
DEMO, use the gas demo to show the compression of a gas.
The three common physical states have some other properties that you should know.
Solids cannot be compressed. This is because the particles that make up the solid are in a rigid structure where the particles are touching. There is no room to compress a solid.
Liquids have very little compressibility. The particles in a liquid are touching, but they are not in a rigid structure. There may be some small amount of room to squeeze the particles together, but NOT very much.
Gasses can be compressed a lot. The particles of a gas are not touching. In fact most of the space is empty. Therefore you can easily compress a gas.
This table summarizes some of the properties of solids liquids and gasses.
DEMO, use the gas demo to show the compression of a gas.
The three common physical states have some other properties that you should know.
Solids cannot be compressed. This is because the particles that make up the solid are in a rigid structure where the particles are touching. There is no room to compress a solid.
Liquids have very little compressibility. The particles in a liquid are touching, but they are not in a rigid structure. There may be some small amount of room to squeeze the particles together, but NOT very much.
Gasses can be compressed a lot. The particles of a gas are not touching. In fact most of the space is empty. Therefore you can easily compress a gas.
17. Tro, Chemistry: A Molecular Approach - Chap 1 17 Solids the particles in a solid are packed close together and are fixed in position
though they may vibrate
the close packing of the particles results in solids being incompressible
the inability of the particles to move around results in solids retaining their shape and volume when placed in a new container, and prevents the particles from flowing
18. Tro, Chemistry: A Molecular Approach - Chap 1 18 Crystalline Solids some solids have their particles arranged in an orderly geometric pattern – we call these crystalline solids
salt and diamonds
19. Tro, Chemistry: A Molecular Approach - Chap 1 19 Amorphous Solids some solids have their particles randomly distributed without any long-range pattern – we call these amorphous solids
plastic
glass
charcoal
20. Tro, Chemistry: A Molecular Approach - Chap 1 20 Liquids the particles in a liquid are closely packed, but they have some ability to move around
the close packing results in liquids being incompressible
but the ability of the particles to move allows liquids to take the shape of their container and to flow – however, they don’t have enough freedom to escape and expand to fill the container
21. Tro, Chemistry: A Molecular Approach - Chap 1 21 Gases in the gas state, the particles have complete freedom from each other
the particles are constantly flying around, bumping into each other and the container
in the gas state, there is a lot of empty space between the particles
22. Tro, Chemistry: A Molecular Approach - Chap 1 22 Gases particles can be squeezed closer together – therefore gases are compressible
particles are not held in close contact and are moving freely, gases expand to fill and take the shape of their container, and will flow
23. Tro, Chemistry: A Molecular Approach - Chap 1 23
24. Tro, Chemistry: A Molecular Approach - Chap 1 24 Classification of Matter by Composition matter whose composition does not change from one sample to another is called a pure substance
made of a single type of atom or molecule
composition is the same, samples have the same characteristics
matter whose composition may vary from one sample to another is called a mixture
two or more types of atoms or molecules combined in variable proportions
because composition varies, samples have different characteristics What is the difference between mixtures and pure substance?
This room contains a mixture of men and women. There is more than one distinct entity.
This side of the room, or this table contains only men. This is only one type of entity.
Elements and compounds are both examples of pure substances, but…
What is the difference between an element and a compound?
An element is a fundamental substance. It has properties that define it, and it cannot be broken down into simpler substances.
Compounds are made of two or more elements in FIXED proportion.
What is the difference between mixtures and pure substance?
This room contains a mixture of men and women. There is more than one distinct entity.
This side of the room, or this table contains only men. This is only one type of entity.
Elements and compounds are both examples of pure substances, but…
What is the difference between an element and a compound?
An element is a fundamental substance. It has properties that define it, and it cannot be broken down into simpler substances.
Compounds are made of two or more elements in FIXED proportion.
25. Tro, Chemistry: A Molecular Approach - Chap 1 25 Classification of Matter by Composition
26. Tro, Chemistry: A Molecular Approach - Chap 1 26 Classification of Pure Substances substances that cannot be broken down into simpler substances by chemical reactions are called elements
basic building blocks of matter
composed of single type of atom All elements are defined by the properties of the single type of atom that makes up that pure substance.
What is an atom. It is the smallest elemental particle that retains the properties of the element.
All of the particles of a sample of an element (for example, copper) have something in common.
Atoms cannot be subdivided without destroying them.
The periodic table is a list of all known elements.
All elements are defined by the properties of the single type of atom that makes up that pure substance.
What is an atom. It is the smallest elemental particle that retains the properties of the element.
All of the particles of a sample of an element (for example, copper) have something in common.
Atoms cannot be subdivided without destroying them.
The periodic table is a list of all known elements.
27. Tro, Chemistry: A Molecular Approach - Chap 1 27 We will spend a great deal of time discussing the elements in another chapter.
As of 2005, there are 116 known elements: 93 occur naturally on earth (including technetium and plutonium), and 94 (including promethium) have been detected in the universe at large.
11 exist under standard conditions as gasses.
2 exist as liquids, the remainder exist as solids.
The 23 elements not found on earth are derived artificially; technetium was the first purportedly non-naturally occurring element to be synthesized, in 1937, although trace amounts of technetium have since been found in nature. All artificially derived elements are radioactive with short half-lives, so if any atoms of these elements were present at the formation of Earth are extremely likely to have already decayed. We will spend a great deal of time discussing the elements in another chapter.
As of 2005, there are 116 known elements: 93 occur naturally on earth (including technetium and plutonium), and 94 (including promethium) have been detected in the universe at large.
11 exist under standard conditions as gasses.
2 exist as liquids, the remainder exist as solids.
The 23 elements not found on earth are derived artificially; technetium was the first purportedly non-naturally occurring element to be synthesized, in 1937, although trace amounts of technetium have since been found in nature. All artificially derived elements are radioactive with short half-lives, so if any atoms of these elements were present at the formation of Earth are extremely likely to have already decayed.
28. Tro, Chemistry: A Molecular Approach - Chap 1 28 Classification of Pure Substances: Cont. substances that can be decomposed are called compounds
chemical combinations of elements
composed of molecules that contain two or more different kinds of atoms
all molecules of a compound are identical, so all samples of a compound behave the same way
most natural pure substances are compounds A compound is a pure substance that is made up of elements in definite proportion.
There is a formula, or recipe that describes which elements and how many of each.
compounds have VERY different chemical and physical properties than the elements from which they were made.
Water, a liquid at RT is made from two gasses, hydrogen and oxygen.
Salt, sodium chloride, a relatively unreactive solid is made from sodium which is a very reactive metal and chlorine which is a reactive and poisonous gas.
A compound is a pure substance that is made up of elements in definite proportion.
There is a formula, or recipe that describes which elements and how many of each.
compounds have VERY different chemical and physical properties than the elements from which they were made.
Water, a liquid at RT is made from two gasses, hydrogen and oxygen.
Salt, sodium chloride, a relatively unreactive solid is made from sodium which is a very reactive metal and chlorine which is a reactive and poisonous gas.
29. Tro, Chemistry: A Molecular Approach - Chap 1 29 Classification of Pure Substances
30. Tro, Chemistry: A Molecular Approach - Chap 1 30 Classification of Mixtures homogeneous = mixture that has uniform composition throughout
every piece of a sample has identical characteristics, though another sample with the same components may have different characteristics
atoms or molecules mixed uniformly
heterogeneous = mixture that does not have uniform composition throughout
contains regions within the sample with different characteristics
atoms or molecules not mixed uniformly If elements and compounds are examples of pure substances,
What are mixtures?
Mixtures are combinations of pure substances where the composition is not fixed.
There are many different names for mixtures. When we dissolve sugar in water we call the resulting mixture a solution.
There are even different types of mixtures…
Homogeneous. Meaning uniform.
Heterogeneous. Not uniform.
If elements and compounds are examples of pure substances,
What are mixtures?
Mixtures are combinations of pure substances where the composition is not fixed.
There are many different names for mixtures. When we dissolve sugar in water we call the resulting mixture a solution.
There are even different types of mixtures…
Homogeneous. Meaning uniform.
Heterogeneous. Not uniform.
31. Tro, Chemistry: A Molecular Approach - Chap 1 31 Classification of Mixtures
32. Tro, Chemistry: A Molecular Approach - Chap 1 32 This flow chart shows the organization of matter into pure substances and mixtures.This flow chart shows the organization of matter into pure substances and mixtures.
33. Tro, Chemistry: A Molecular Approach - Chap 1 33 Separation of Mixtures separate mixtures based on different physical properties of the components
Physical change
34. Tro, Chemistry: A Molecular Approach - Chap 1 34 Distillation
35. Tro, Chemistry: A Molecular Approach - Chap 1 35 Filtration
36. Tro, Chemistry: A Molecular Approach - Chap 1 36 Changes in Matter changes that alter the state or appearance of the matter without altering the composition are called physical changes
changes that alter the composition of the matter are called chemical changes
during the chemical change, the atoms that are present rearrange into new molecules, but all of the original atoms are still present Matter can undergo changes.
Physical changes describe a change in the substance that does not alter the composition of the substance.
If we melt an ice cube, the substance itself does not change. Before melting we had a cube of solid water. After we melt the ice cube we have a puddle of liquid water. The substance is still water.
Boiling is another example of a physical change.
Cutting a substance into smaller pieces does not alter the substance. If we take a piece of lumber and cut it into smaller pieces, the substance is still wood. Even the sawdust is still wood pieces. The substance has not changed.
Chemical changes are a change in matter the alters the composition of the substance. After a chemical change we have a new substance with new properties. Or we may even have a mixture of two or more new substances with their own properties.
Matter can undergo changes.
Physical changes describe a change in the substance that does not alter the composition of the substance.
If we melt an ice cube, the substance itself does not change. Before melting we had a cube of solid water. After we melt the ice cube we have a puddle of liquid water. The substance is still water.
Boiling is another example of a physical change.
Cutting a substance into smaller pieces does not alter the substance. If we take a piece of lumber and cut it into smaller pieces, the substance is still wood. Even the sawdust is still wood pieces. The substance has not changed.
Chemical changes are a change in matter the alters the composition of the substance. After a chemical change we have a new substance with new properties. Or we may even have a mixture of two or more new substances with their own properties.
37. Tro, Chemistry: A Molecular Approach - Chap 1 37 Physical Changes in Matter
38. Tro, Chemistry: A Molecular Approach - Chap 1 38 Common Physical Changes processes that cause changes in the matter that do not change its composition
state changes
boiling / condensing
melting / freezing
subliming
39. Tro, Chemistry: A Molecular Approach - Chap 1 39 Chemical Changes in Matter
40. Tro, Chemistry: A Molecular Approach - Chap 1 40 Common Chemical Changes processes that cause changes in the matter that change its composition
rusting
processes that release lots of energy
burning
41. Tro, Chemistry: A Molecular Approach - Chap 1 41 Properties of Matter physical properties are the characteristics of matter that can be changed without changing its composition
characteristics that are directly observable
chemical properties are the characteristics that determine how the composition of matter changes as a result of contact with other matter or the influence of energy
characteristics that describe the behavior of matter
All substances have properties that we can observe. These properties are what identify the substance and distinguish it from other substances.
There are two classes of properties. Physical properties and chemical properties.
All substances have properties that we can observe. These properties are what identify the substance and distinguish it from other substances.
There are two classes of properties. Physical properties and chemical properties.
42. Tro, Chemistry: A Molecular Approach - Chap 1 42 Energy Changes in Matter changes in matter, both physical and chemical, result in the matter either gaining or releasing energy
energy is the capacity to do work
work is the action of a force applied across a distance
a force is a push or a pull on an object
electrostatic force is the push or pull on objects that have an electrical charge Energy is a measure of an object or systems potential to do work.
Work is the application of a force over a distance.
Try to remember these definitions as we discuss matter in this chapter.
Energy is a measure of an object or systems potential to do work.
Work is the application of a force over a distance.
Try to remember these definitions as we discuss matter in this chapter.
43. Tro, Chemistry: A Molecular Approach - Chap 1 43 Energy of Matter all matter possesses energy
energy is classified as either kinetic or potential
energy can be converted from one form to another
when matter undergoes a chemical or physical change, the amount of energy in the matter changes as well There are many different types of energy.
Kinetic energy is the energy that matter has due to its motion or velocity.
KE = ˝mv2
Potential energy is energy stored in the matter due to several factors.
You can have gravitational potential energy.
Electrical potential energy
Magnetic potential energy
Chemical potential energy
There are many different types of energy.
Kinetic energy is the energy that matter has due to its motion or velocity.
KE = ˝mv2
Potential energy is energy stored in the matter due to several factors.
You can have gravitational potential energy.
Electrical potential energy
Magnetic potential energy
Chemical potential energy
44. Tro, Chemistry: A Molecular Approach - Chap 1 44 Energy of Matter - Kinetic kinetic energy is energy of motion
motion of the atoms, molecules, and subatomic particles
thermal (heat) energy is a form of kinetic energy because it is caused by molecular motion
45. Tro, Chemistry: A Molecular Approach - Chap 1 45 Energy of Matter - Potential potential energy is energy that is stored in the matter
due to the composition of the matter and its position in the universe
chemical potential energy arises from electrostatic forces between atoms, molecules, and subatomic particles
46. Tro, Chemistry: A Molecular Approach - Chap 1 46 Conversion of Energy you can interconvert kinetic energy and potential energy
whatever process you do that converts energy from one type or form to another, the total amount of energy remains the same
Law of Conservation of Energy
The first law of thermodynamics is the law of conservation of energy.
The law of conservation of energy States that energy cannot be created or destroyed in a chemical reaction, it is only converted between forms or moved from one location to another.
The first law of thermodynamics is the law of conservation of energy.
The law of conservation of energy States that energy cannot be created or destroyed in a chemical reaction, it is only converted between forms or moved from one location to another.
47. Tro, Chemistry: A Molecular Approach - Chap 1 47 Spontaneous Processes materials that possess high potential energy are less stable
processes in nature tend to occur on their own when the result is material(s) with lower total potential energy
processes that result in materials with higher total potential energy can occur, but generally will not happen without input of energy from an outside source
when a process results in materials with less potential energy at the end than there was at the beginning, the difference in energy is released into the environment
48. Tro, Chemistry: A Molecular Approach - Chap 1 48 Potential to Kinetic Energy
49. Tro, Chemistry: A Molecular Approach - Chap 1 49
50. Tro, Chemistry: A Molecular Approach - Chap 1 50 Question What do scientists measure?
Right! Things like how many licks it takes to get to the center of a tootsie-pop
According to the preeminent source of information in the world… google… scientists measure…
Well they measure a lot of stuff.What do scientists measure?
Right! Things like how many licks it takes to get to the center of a tootsie-pop
According to the preeminent source of information in the world… google… scientists measure…
Well they measure a lot of stuff.
51. Tro, Chemistry: A Molecular Approach - Chap 1 51 The Standard Units Scientists have agreed on a set of international standard units for comparing all our measurements called the SI units
Systčme International = International System Lets take a look at the base units.
These are the seven fundamental units in the SI system.
Read and explain the units.
Lets take a look at the base units.
These are the seven fundamental units in the SI system.
Read and explain the units.
52. Tro, Chemistry: A Molecular Approach - Chap 1 52 Length Measure of the two-dimensional distance an object covers
often need to measure lengths that are very long (distances between stars) or very short (distances between atoms)
SI unit = meter
About 3.37 inches longer than a yard
1 meter = one ten-millionth the distance from the North Pole to the Equator = distance between marks on standard metal rod = distance traveled by light in a specific period of time
Commonly use centimeters (cm)
1 m = 100 cm
1 cm = 0.01 m = 10 mm
1 inch = 2.54 cm (exactly) The SI unit of length is the meter (m)
1 foot = 0.3048 meters
1 ft = 0.3048 m
It is important that you have an understanding of the relative size of the common units of length.
The SI unit of length is the meter (m)
1 foot = 0.3048 meters
1 ft = 0.3048 m
It is important that you have an understanding of the relative size of the common units of length.
53. Tro, Chemistry: A Molecular Approach - Chap 1 53 Mass Measure of the amount of matter present in an object
weight measures the gravitational pull on an object, which depends on its mass
SI unit = kilogram (kg)
about 2 lbs. 3 oz.
Commonly measure mass in grams (g) or milligrams (mg)
1 kg = 2.2046 pounds, 1 lbs. = 453.59 g
1 kg = 1000 g = 103 g
1 g = 1000 mg = 103 mg
1 g = 0.001 kg = 10-3 kg
1 mg = 0.001 g = 10-3 g
54. Tro, Chemistry: A Molecular Approach - Chap 1 54
55. Tro, Chemistry: A Molecular Approach - Chap 1 55 Time measure of the duration of an event
SI units = second (s)
1 s is defined as the period of time it takes for a specific number of radiation events of a specific transition from cesium-133
56. Tro, Chemistry: A Molecular Approach - Chap 1 56 Temperature measure of the average amount of kinetic energy
higher temperature = larger average kinetic energy
heat flows from the matter that has high thermal energy into matter that has low thermal energy
until they reach the same temperature
heat is exchanged through molecular collisions between the two materials
57. Tro, Chemistry: A Molecular Approach - Chap 1 57 Temperature Scales Fahrenheit Scale, °F
used in the U.S.
Celsius Scale, °C
used in all other countries
Kelvin Scale, K
absolute scale
no negative numbers
directly proportional to average amount of kinetic energy
0 K = absolute zero Notice in this graphic that since the Kelvin scale is based on the Celsius scale the amount of temperature change per division on the scale is the same, but the label, or number that corresponds to that temperature is different.
Notice in this graphic that since the Kelvin scale is based on the Celsius scale the amount of temperature change per division on the scale is the same, but the label, or number that corresponds to that temperature is different.
58. Tro, Chemistry: A Molecular Approach - Chap 1 58 Here is another comparison of the temperature scales which show a few more temperatures for comparison.Here is another comparison of the temperature scales which show a few more temperatures for comparison.
59. Tro, Chemistry: A Molecular Approach - Chap 1 59 Again, another graphic that shows the relationship between the freezing point of water and the different temperature scales used.Again, another graphic that shows the relationship between the freezing point of water and the different temperature scales used.
60. Tro, Chemistry: A Molecular Approach - Chap 1 60 Kelvin vs. Celsius the size of a “degree” on the Kelvin scale is the same as on the Celsius scale
though technically, we don’t call the divisions on the Kelvin scale degrees; we called them kelvins!
so 1 kelvin is 1.8 times larger than 1°F
the 0 standard on the Kelvin scale is a much lower temperature than on the Celsius scale Because the temperature scales have different zero points, formulas must be used to carry out the conversions.
In order to convert between Celsius and Kelvin you must add 273.15 to the Celsius reading. To convert from Kelvin to Celsius, you reverse the process and subtract 273.15 from the Kelvin reading.
Because the temperature scales have different zero points, formulas must be used to carry out the conversions.
In order to convert between Celsius and Kelvin you must add 273.15 to the Celsius reading. To convert from Kelvin to Celsius, you reverse the process and subtract 273.15 from the Kelvin reading.
61. Tro, Chemistry: A Molecular Approach - Chap 1 61 Fahrenheit vs. Celsius a Celsius degree is 1.8 times larger than a Fahrenheit degree
the standard used for 0° on the Fahrenheit scale is a lower temperature than the standard used for 0° on the Celsius scale Since the graduations on the Fahrenheit scale and Celsius scale the conversion is more difficult.
Since the graduations on the Fahrenheit scale and Celsius scale the conversion is more difficult.
62. Example 1.2 Convert 40.00 °C into K and °F
63. Tro, Chemistry: A Molecular Approach - Chap 1 63 Related Units in the SI System All units in the SI system are related to the standard unit by a power of 10
The power of 10 is indicated by a prefix multiplier
The prefix multipliers are always the same, regardless of the standard unit
Report measurements with a unit that is close to the size of the quantity being measured In order to be able to communicate with other scientists, we must have a logical and universal system for comparing measurements.
The most common system is called the Metric system.
Also known as the International system or Systeme International (SI system for short)
It is a system arranged on powers of 10.
For every fundamental measurement there is a base unit. In order to describe measurements that are smaller or larger than the base, we use powers of 10.
In order to be able to communicate with other scientists, we must have a logical and universal system for comparing measurements.
The most common system is called the Metric system.
Also known as the International system or Systeme International (SI system for short)
It is a system arranged on powers of 10.
For every fundamental measurement there is a base unit. In order to describe measurements that are smaller or larger than the base, we use powers of 10.
64. Tro, Chemistry: A Molecular Approach - Chap 1 64 Prefixes Used with SI Units There are prefixes to the SI units; often the regular units are too small or too large for our use.
Common prefixes
SI Base Units
giga 109
Mega 106
Kilo 103
Centi 10-2
Milli 10-3
Micro 10-6
Nano 10-9
These prefixes allow us to use units like
Centimeter
Kilogram
Milliliter
Notice that each prefix has an exponential power or notation.
1 kilogram means the same as 1x103 grams
1 microgram means the same as 1x10-6 gramsThere are prefixes to the SI units; often the regular units are too small or too large for our use.
Common prefixes
SI Base Units
giga 109
Mega 106
Kilo 103
Centi 10-2
Milli 10-3
Micro 10-6
Nano 10-9
65. Tro, Chemistry: A Molecular Approach - Chap 1 65 Volume Derived unit
any length unit cubed
Measure of the amount of space occupied
SI unit = cubic meter (m3)
Commonly measure solid volume in cubic centimeters (cm3)
1 m3 = 106 cm3
1 cm3 = 10-6 m3 = 0.000001 m3
Commonly measure liquid or gas volume in milliliters (mL)
1 L is slightly larger than 1 quart
1 L = 1 dm3 = 1000 mL = 103 mL
1 mL = 0.001 L = 10-3 L
1 mL = 1 cm3
66. Tro, Chemistry: A Molecular Approach - Chap 1 66 Here is that relationship pictorally.Here is that relationship pictorally.
67. Tro, Chemistry: A Molecular Approach - Chap 1 67 Common Units and Their Equivalents
68. Tro, Chemistry: A Molecular Approach - Chap 1 68 Common Units and Their Equivalents
69. Tro, Chemistry: A Molecular Approach - Chap 1 69 Intensive Properties Do not depend on the amount of substance.
Melting point
Boiling point
Color
Flammability
Reactivity
Conductivity
Physical State (solid, liquid, gas) The properties of substances can be classified by two other terms.
Intensive and extensive.
Intensive properties DO NOT depend on the amount of material.
For example, melting point or boiling point. It does not matter if you have 1 gram of water or one ton of water. Water melts at 0oC and boils at 100oC.
Color is another intensive property.
Flammability, reactivity, conductivity,
Intensive properties can be a physical property or a chemical property.The properties of substances can be classified by two other terms.
Intensive and extensive.
Intensive properties DO NOT depend on the amount of material.
For example, melting point or boiling point. It does not matter if you have 1 gram of water or one ton of water. Water melts at 0oC and boils at 100oC.
Color is another intensive property.
Flammability, reactivity, conductivity,
Intensive properties can be a physical property or a chemical property.
70. Tro, Chemistry: A Molecular Approach - Chap 1 70 Extensive Properties Depend on the amount of material present
Mass
Volume
Length
Moles
Weight
Total amount of heat given off in combustion Extensive properties are properties that depend upon the amount of the substance present.
For example, Mass. This is logical. The greater the amount of a substance present, the greater the sample’s mass.
Volume, length, moles, weight. All examples of extensive properties.
Many measurements can depend upon the amount of substance present. The total heat given off in a combustion reaction. For example, on a cool autumn evening, would you like to be gathered around a nice campfire, a lit match, or in the middle of a raging forest fire?
Again extensive properties can be a chemical property or a physical property.
Extensive properties are properties that depend upon the amount of the substance present.
For example, Mass. This is logical. The greater the amount of a substance present, the greater the sample’s mass.
Volume, length, moles, weight. All examples of extensive properties.
Many measurements can depend upon the amount of substance present. The total heat given off in a combustion reaction. For example, on a cool autumn evening, would you like to be gathered around a nice campfire, a lit match, or in the middle of a raging forest fire?
Again extensive properties can be a chemical property or a physical property.
71. Tro, Chemistry: A Molecular Approach - Chap 1 71 Mass & Volume two main physical properties of matter
mass and volume are extensive properties
the value depends on the quantity of matter
extensive properties cannot be used to identify what type of matter something is
if you are given a large glass containing 100 g of a clear, colorless liquid and a small glass containing 25 g of a clear, colorless liquid - are both liquids the same stuff?
even though mass and volume are individual properties, for a given type of matter they are related to each other!
72. Tro, Chemistry: A Molecular Approach - Chap 1 72 Mass vs. Volume of Brass
73. Tro, Chemistry: A Molecular Approach - Chap 1 73
74. Tro, Chemistry: A Molecular Approach - Chap 1 74 Density Ratio of mass:volume is an intensive property
value independent of the quantity of matter
Solids = g/cm3
1 cm3 = 1 mL
Liquids = g/mL
Gases = g/L
Volume of a solid can be determined by water displacement – Archimedes Principle
Density : solids > liquids >>> gases
except ice is less dense than liquid water!
Density is a very important property of matter. It is a derived unit and is defined as the mass of an object divided by its volume. Density is a measure of how compact or tightly packed an object is. In SI units, density is kg/m3, but often we use more convenient units of grams/ml.
Specific gravity is a comparison of the density of an object to the density of water. Since the density of water is 1.00 g/ml, the specific gravity of a substance is a unitless number.
Density is a very important property of matter. It is a derived unit and is defined as the mass of an object divided by its volume. Density is a measure of how compact or tightly packed an object is. In SI units, density is kg/m3, but often we use more convenient units of grams/ml.
Specific gravity is a comparison of the density of an object to the density of water. Since the density of water is 1.00 g/ml, the specific gravity of a substance is a unitless number.
75. Tro, Chemistry: A Molecular Approach - Chap 1 75 Density For equal volumes, denser object has larger mass
For equal masses, denser object has smaller volume
Heating an object generally causes it to expand, therefore the density changes with temperature
76. Example 1.3 Decide if a ring with a mass of 3.15 g that displaces 0.233 cm3 of water is platinum
77. Tro, Chemistry: A Molecular Approach - Chap 1 77
78. Tro, Chemistry: A Molecular Approach - Chap 1 78 Measurement Components of Measurement
Numerical quantity
Unit
Name of substance
For example,
325.0 mL water Every measurement has some essential components.
First there has to be a number, the measurement,
I have 7.
7 what. Second there has to be a unit.
7 cans. 7 pairs. 7 pounds.
Finally there has to be a description of the thing that was measured. A name.
Every measurement has some essential components.
First there has to be a number, the measurement,
I have 7.
7 what. Second there has to be a unit.
7 cans. 7 pairs. 7 pounds.
Finally there has to be a description of the thing that was measured. A name.
79. Tro, Chemistry: A Molecular Approach - Chap 1 79 Components of Measurement Components of a Measurement
Numerical Quantity, Unit, Name of substance
All three of these components of the measurement are very important. Every measurement has some essential components,
First there has to be a number. The measurement:
“I have 7”
But a number itself is not a measurement… “7 what”
“7 pounds, 7 feet, 7 amps…”
There has to be a unit.
Finally we need a name or a discriptor of the thing being measured. “I have 7 pounds of pennies, 7 pounds of jelly beans, 7 pounds of gourmet coffee”
Without any one of these three things, a measurement is meaningless.
Just ask NASA! Do you remember the $125 Mars orbiter that crashed into the Mars surface in 1999. The failure was due to the two teams working on the lander not conveying all the information about a length measurement to one another.
NASA's metric confusion caused Mars orbiter loss
NASA's Climate Orbiter was lost September 23, 1999
September 30, 1999 Web posted at: 1:46 p.m. EDT (1746 GMT)
(CNN) -- NASA lost a $125 million Mars orbiter because one engineering team used metric units while another used English units for a key spacecraft operation, according to a review finding released Thursday.
For that reason, information failed to transfer between the Mars Climate Orbiter spacecraft team at Lockheed Martin in Colorado and the mission navigation team in California. Lockheed Martin built the spacecraft. Every measurement has some essential components,
First there has to be a number. The measurement:
“I have 7”
But a number itself is not a measurement… “7 what”
“7 pounds, 7 feet, 7 amps…”
There has to be a unit.
Finally we need a name or a discriptor of the thing being measured. “I have 7 pounds of pennies, 7 pounds of jelly beans, 7 pounds of gourmet coffee”
Without any one of these three things, a measurement is meaningless.
Just ask NASA! Do you remember the $125 Mars orbiter that crashed into the Mars surface in 1999. The failure was due to the two teams working on the lander not conveying all the information about a length measurement to one another.
NASA's metric confusion caused Mars orbiter loss
NASA's Climate Orbiter was lost September 23, 1999
September 30, 1999Web posted at: 1:46 p.m. EDT (1746 GMT)
(CNN) -- NASA lost a $125 million Mars orbiter because one engineering team used metric units while another used English units for a key spacecraft operation, according to a review finding released Thursday.
For that reason, information failed to transfer between the Mars Climate Orbiter spacecraft team at Lockheed Martin in Colorado and the mission navigation team in California. Lockheed Martin built the spacecraft.
80. Tro, Chemistry: A Molecular Approach - Chap 1 80 What Is a Measurement? quantitative observation
comparison to an agreed- upon standard
every measurement has a number and a unit
81. Tro, Chemistry: A Molecular Approach - Chap 1 81 A Measurement the unit tells you what standard you are comparing your object to
the number tells you
what multiple of the standard the object measures
the uncertainty in the measurement
scientific measurements are reported so that every digit written is certain, except the last one which is estimated
82. Tro, Chemistry: A Molecular Approach - Chap 1 82 Estimating the Last Digit for instruments marked with a scale, you get the last digit by estimating between the marks
if possible
mentally divide the space into 10 equal spaces, then estimate how many spaces over the indicator mark is
83. Tro, Chemistry: A Molecular Approach - Chap 1 83 When you read a buret, a graduated cylinder, or a graduated pipet, you must try to read the meniscus of the liquid inside the device. most of the time, the meniscus does not match exactly with one of the graduations on the device. You must therefore estimate the position of the meniscus.
In this example the level of the meniscus is between the 6.2 ml mark and the 6.3 ml mark.
One person may look at the level of the liquid and estimate that the meniscus is at 6.23. Another may estimate that it is at 6.22.
The last digit in your reading is not certain. You are certain that it is more than 6.2 ml, but you are not 100% certain how much more.When you read a buret, a graduated cylinder, or a graduated pipet, you must try to read the meniscus of the liquid inside the device. most of the time, the meniscus does not match exactly with one of the graduations on the device. You must therefore estimate the position of the meniscus.
In this example the level of the meniscus is between the 6.2 ml mark and the 6.3 ml mark.
One person may look at the level of the liquid and estimate that the meniscus is at 6.23. Another may estimate that it is at 6.22.
The last digit in your reading is not certain. You are certain that it is more than 6.2 ml, but you are not 100% certain how much more.
84. Tro, Chemistry: A Molecular Approach - Chap 1 84
85. Tro, Chemistry: A Molecular Approach - Chap 1 85 The # of S.F. Depends Upon the Device The precision of the device is dependant upon how the device was constructed.
Here is an example of two different thermometers. The one on the left was made with very fine graduations. The gradutations represent a tenth of a degree. The one on the right was made with graduations that represent single degrees. When both thermometers are reading the temperature of the same object, a person reading the scales is able to read the one on the left with more precision.The precision of the device is dependant upon how the device was constructed.
Here is an example of two different thermometers. The one on the left was made with very fine graduations. The gradutations represent a tenth of a degree. The one on the right was made with graduations that represent single degrees. When both thermometers are reading the temperature of the same object, a person reading the scales is able to read the one on the left with more precision.
86. Tro, Chemistry: A Molecular Approach - Chap 1 86 Significant Figures the non-place-holding digits in a reported measurement are called significant figures
some zeros in a written number are only there to help you locate the decimal point
significant figures tell us the range of values to expect for repeated measurements
the more significant figures there are in a measurement, the smaller the range of values is When we make measurements, we MUST report our data in a method so that others know by looking at the data how much certainty we have that our measurement represents the true value for the quantity we were measuring.
The Significant figures in a measurement are those digits in a measured number including all certain
digits plus a final one, which is semi-uncertain.
It is easiest to see how significant figures
When we make measurements, we MUST report our data in a method so that others know by looking at the data how much certainty we have that our measurement represents the true value for the quantity we were measuring.
The Significant figures in a measurement are those digits in a measured number including all certain
digits plus a final one, which is semi-uncertain.
It is easiest to see how significant figures
87. Tro, Chemistry: A Molecular Approach - Chap 1 87 Counting Significant Figures All non-zero digits are significant
1.5 has 2 sig. figs.
Interior zeros are significant
1.05 has 3 sig. figs.
Leading zeros are NOT significant
0.001050 has 4 sig. figs.
1.050 x 10-3
These are the rules for finding the number of significant figures in a measurement.
1. nonzero digits are always significant
2. captive zeros must be significant, these are zeros that are stuck in between two non-zero digits.
3. leading zeros are not significant, these zeros are only there to hold place. These are the rules for finding the number of significant figures in a measurement.
1. nonzero digits are always significant
2. captive zeros must be significant, these are zeros that are stuck in between two non-zero digits.
3. leading zeros are not significant, these zeros are only there to hold place.
88. Tro, Chemistry: A Molecular Approach - Chap 1 88 Counting Significant Figures Trailing zeros may or may not be significant
Trailing zeros after a decimal point are significant
1.050 has 4 sig. figs.
Zeros at the end of a number without a written decimal point are ambiguous and should be avoided by using scientific notation
if 150 has 2 sig. figs. then 1.5 x 102
but if 150 has 3 sig. figs. then 1.50 x 102 4. trailing zeros are significant if there is a decimal point.
5. The rule that causes all the problems is this last rule, zeros at end, no decimal point ???
4. trailing zeros are significant if there is a decimal point.
5. The rule that causes all the problems is this last rule, zeros at end, no decimal point ???
89. Tro, Chemistry: A Molecular Approach - Chap 1 89 Significant Figures and Exact Numbers Exact numbers have an unlimited number of significant figures
A number whose value is known with complete certainty is exact
from counting individual objects
from definitions
1 cm is exactly equal to 0.01 m
from integer values in equations
in the equation for the radius of a circle, the 2 is exact
Exact number is a number that arises from either counting items or defining a unit or a formula with an integer value.
There are No uncertainties at all in exact numbers (hence their name).
Do not apply to the significant figures rule.
Exact number is a number that arises from either counting items or defining a unit or a formula with an integer value.
There are No uncertainties at all in exact numbers (hence their name).
Do not apply to the significant figures rule.
90. Tro, Chemistry: A Molecular Approach - Chap 1 90 Example 1.5 Determining the Number of Significant Figures in a Number
91. Tro, Chemistry: A Molecular Approach - Chap 1 91 Multiplication and Division with Significant Figures when multiplying or dividing measurements with significant figures, the result has the same number of significant figures as the measurement with the fewest number of significant figures
5.02 × 89,665 × 0.10 = 45.0118 = 45
3 sig. figs. 5 sig. figs. 2 sig. figs. 2 sig. figs.
5.892 ÷ 6.10 = 0.96590 = 0.966
4 sig. figs. 3 sig. figs. 3 sig. figs.
There are also rules for determining the number of significant figures in an answer when you conduct multiplication or division.
Multiplication and division: give the answer in significant figures as the measurement with the least amount of significant figures.
There are also rules for determining the number of significant figures in an answer when you conduct multiplication or division.
Multiplication and division: give the answer in significant figures as the measurement with the least amount of significant figures.
92. Tro, Chemistry: A Molecular Approach - Chap 1 92 Addition and Subtraction with Significant Figures when adding or subtracting measurements with significant figures, the result has the same number of decimal places as the measurement with the fewest number of decimal places
5.74 + 0.823 + 2.651 = 9.214 = 9.21
2 dec. pl. 3 dec. pl. 3 dec. pl. 2 dec. pl.
4.8 - 3.965 = 0.835 = 0.8
1 dec. pl 3 dec. pl. 1 dec. pl.
There are rules for determining the number of significant figures in an answer when you conduct addition or subtraction.
Addition and subtraction: give the answer in as many decimal places as that of the smallest number
There are rules for determining the number of significant figures in an answer when you conduct addition or subtraction.
Addition and subtraction: give the answer in as many decimal places as that of the smallest number
93. Tro, Chemistry: A Molecular Approach - Chap 1 93 Rounding when rounding to the correct number of significant figures, if the number after the place of the last significant figure is
0 to 4, round down
drop all digits after the last sig. fig. and leave the last sig. fig. alone
add insignificant zeros to keep the value if necessary
5 to 9, round up
drop all digits after the last sig. fig. and increase the last sig. fig. by one
add insignificant zeros to keep the value if necessary
to avoid accumulating extra error from rounding, round only at the end, keeping track of the last sig. fig. for intermediate calculations When you conduct some mathematical manipulation as we have seen in the previous examples, you need to round your answer so that you have the correct number of significant figures.
When you conduct some mathematical manipulation as we have seen in the previous examples, you need to round your answer so that you have the correct number of significant figures.
94. Tro, Chemistry: A Molecular Approach - Chap 1 94 Rounding rounding to 2 significant figures
2.34 rounds to 2.3
because the 3 is where the last sig. fig. will be and the number after it is 4 or less
2.37 rounds to 2.4
because the 3 is where the last sig. fig. will be and the number after it is 5 or greater
2.349865 rounds to 2.3
because the 3 is where the last sig. fig. will be and the number after it is 4 or less
95. Tro, Chemistry: A Molecular Approach - Chap 1 95 Rounding rounding to 2 significant figures
0.0234 rounds to 0.023 or 2.3 × 10-2
because the 3 is where the last sig. fig. will be and the number after it is 4 or less
0.0237 rounds to 0.024 or 2.4 × 10-2
because the 3 is where the last sig. fig. will be and the number after it is 5 or greater
0.02349865 rounds to 0.023 or 2.3 × 10-2
because the 3 is where the last sig. fig. will be and the number after it is 4 or less
96. Tro, Chemistry: A Molecular Approach - Chap 1 96 Rounding rounding to 2 significant figures
234 rounds to 230 or 2.3 × 102
because the 3 is where the last sig. fig. will be and the number after it is 4 or less
237 rounds to 240 or 2.4 × 102
because the 3 is where the last sig. fig. will be and the number after it is 5 or greater
234.9865 rounds to 230 or 2.3 × 102
because the 3 is where the last sig. fig. will be and the number after it is 4 or less
97. Tro, Chemistry: A Molecular Approach - Chap 1 97 Both Multiplication/Division and Addition/Subtraction with Significant Figures when doing different kinds of operations with measurements with significant figures, do whatever is in parentheses first, evaluate the significant figures in the intermediate answer, then do the remaining steps
3.489 × (5.67 – 2.3) =
2 dp 1 dp
3.489 × 3.37 = 12
4 sf 1 dp & 2 sf 2 sf
98. Tro, Chemistry: A Molecular Approach - Chap 1 98 Example 1.6 Perform the following calculations to the correct number of significant figures
99. Tro, Chemistry: A Molecular Approach - Chap 1 99 Example 1.6 Perform the following calculations to the correct number of significant figures
100. Tro, Chemistry: A Molecular Approach - Chap 1 100 How many SF’s should be in the following answer? Although it is common practice in a multi-step problem to work out the answer on your calculator and then round the answer to some number of significant figures, this is not always a good idea.
How many SF’s should be in the following answer?Although it is common practice in a multi-step problem to work out the answer on your calculator and then round the answer to some number of significant figures, this is not always a good idea.
How many SF’s should be in the following answer?
101. Tro, Chemistry: A Molecular Approach - Chap 1 101
102. Tro, Chemistry: A Molecular Approach - Chap 1 102 Uncertainty in Measured Numbers uncertainty comes from limitations of the instruments used for comparison, the experimental design, the experimenter, and nature’s random behavior
to understand how reliable a measurement is we need to understand the limitations of the measurement
accuracy is an indication of how close a measurement comes to the actual value of the quantity
precision is an indication of how reproducible a measurement is In the process of making any comparative measurement, there is some amount of uncertainty that comes from a combination the tool and the user.
Precision- closeness of a set of values obtained from identical measurements
Degree that measurements agree with one another
Accuracy- closeness of a single measurement to its true value
In the process of making any comparative measurement, there is some amount of uncertainty that comes from a combination the tool and the user.
Precision- closeness of a set of values obtained from identical measurements
Degree that measurements agree with one another
Accuracy- closeness of a single measurement to its true value
103. Tro, Chemistry: A Molecular Approach - Chap 1 103 Uncertainty in Measurement Systematic Error (SE) -
Values that are either all higher or all lower than the actual value
Random Error (RE) -
In the absence of SE, some values that are higher and some that are lower than the actual value
Uncertainty in our measurements comes from two different sources…
Systematic error or random error.
Random errors are statistical fluctuations (in either direction) in the measured data due to the precision limitations of the measurement device. Random errors usually result from the experimenter's inability to take the same measurement in exactly the same way to get exact the same number.
Systematic errors, by contrast, are reproducible inaccuracies that yields results that are all too high or too low. Systematic errors are often due to a problem which persists throughout the entire experiment.
Uncertainty in our measurements comes from two different sources…
Systematic error or random error.
Random errors are statistical fluctuations (in either direction) in the measured data due to the precision limitations of the measurement device. Random errors usually result from the experimenter's inability to take the same measurement in exactly the same way to get exact the same number.
Systematic errors, by contrast, are reproducible inaccuracies that yields results that are all too high or too low. Systematic errors are often due to a problem which persists throughout the entire experiment.
104. Tro, Chemistry: A Molecular Approach - Chap 1 104 Precision imprecision in measurements is caused by random errors
errors that result from random fluctuations
no specific cause, therefore cannot be corrected
we determine the precision of a set of measurements by evaluating how far they are from the actual value and each other
even though every measurement has some random error, with enough measurements these errors should average out
105. Tro, Chemistry: A Molecular Approach - Chap 1 105 Accuracy inaccuracy in measurement caused by systematic errors
errors caused by limitations in the instruments or techniques or experimental design
can be reduced by using more accurate instruments, or better technique or experimental design
we determine the accuracy of a measurement by evaluating how far it is from the actual value
systematic errors do not average out with repeated measurements because they consistently cause the measurement to be either too high or too low
106. Tro, Chemistry: A Molecular Approach - Chap 1 106 When making measurement, it is important to eliminate (as much a possible) any sources of uncertainty.
This is part of the systematic process that we use called the scientific method. We are interested in investigating something and controlling the variables.
This graphic shows the differences between accuracy and precision.
It is possible to be very precise, but not accurate. This is probably the result of systematic error. A balance was not calibrated correctly. You measuring device has some problem.
When making measurement, it is important to eliminate (as much a possible) any sources of uncertainty.
This is part of the systematic process that we use called the scientific method. We are interested in investigating something and controlling the variables.
This graphic shows the differences between accuracy and precision.
It is possible to be very precise, but not accurate. This is probably the result of systematic error. A balance was not calibrated correctly. You measuring device has some problem.
107. Tro, Chemistry: A Molecular Approach - Chap 1 107 Accuracy vs. Precision
108. Tro, Chemistry: A Molecular Approach - Chap 1 108 Random or Systematic? Take a look at these graphs.
Can you identify which one has random error in the data and which one has a systematic error?Take a look at these graphs.
Can you identify which one has random error in the data and which one has a systematic error?
109. Tro, Chemistry: A Molecular Approach - Chap 1 109 Precise and Accurate? Which ones of these graphs shows data that is precise?
Which ones of these graphs shows data that is accurate?
Which ones of these graphs shows data that is precise?
Which ones of these graphs shows data that is accurate?
110. Tro, Chemistry: A Molecular Approach - Chap 1 110 Units Always write every number with its associated unit
Always include units in your calculations
you can do the same kind of operations on units as you can with numbers
cm × cm = cm2
cm + cm = cm
cm ÷ cm = 1
using units as a guide to problem solving is called dimensional analysis
111. Tro, Chemistry: A Molecular Approach - Chap 1 111 Problem Solving and Dimensional Analysis Many problems in chemistry involve using relationships to convert one unit of measurement to another
Conversion factors are relationships between two units
May be exact or measured
Conversion factors generated from equivalence statements
e.g., 1 inch = 2.54 cm can give or
112. Tro, Chemistry: A Molecular Approach - Chap 1 112 Problem Solving and Dimensional Analysis Arrange conversion factors so given unit cancels
Arrange conversion factor so given unit is on the bottom of the conversion factor
May string conversion factors
So we do not need to know every relationship, as long as we can find something else the given and desired units are related to
113. Tro, Chemistry: A Molecular Approach - Chap 1 113 Conceptual Plan a conceptual plan is a visual outline that shows the strategic route required to solve a problem
for unit conversion, the conceptual plan focuses on units and how to convert one to another
for problems that require equations, the conceptual plan focuses on solving the equation to find an unknown value
114. Tro, Chemistry: A Molecular Approach - Chap 1 114 Concept Plans and Conversion Factors Convert inches into centimeters
Find relationship equivalence: 1 in = 2.54 cm
Write concept plan
115. Tro, Chemistry: A Molecular Approach - Chap 1 115 Systematic Approach Sort the information from the problem
identify the given quantity and unit, the quantity and unit you want to find, any relationships implied in the problem
Design a strategy to solve the problem
Concept plan
sometimes may want to work backwards
each step involves a conversion factor or equation
Apply the steps in the concept plan
check that units cancel properly
multiply terms across the top and divide by each bottom term
Check the answer
double check the set-up to ensure the unit at the end is the one you wished to find
check to see that the size of the number is reasonable
since centimeters are smaller than inches, converting inches to centimeters should result in a larger number
116. Example 1.7 Convert 1.76 yd. to centimeters
117. Tro, Chemistry: A Molecular Approach - Chap 1 117 Practice – Convert 30.0 mL to quarts (1 L = 1.057 qt)
118. Convert 30.0 mL to quarts
119. Tro, Chemistry: A Molecular Approach - Chap 1 119 Concept Plans for Units Raised to Powers Convert cubic inches into cubic centimeters
Find relationship equivalence: 1 in = 2.54 cm
Write concept plan
120. Example 1.9 Convert 5.70 L to cubic inches
121. Tro, Chemistry: A Molecular Approach - Chap 1 121 Practice 1.9 How many cubic centimeters are there in 2.11 yd3?
122. Practice 1.9 Convert 2.11 yd3 to cubic centimeters
123. Tro, Chemistry: A Molecular Approach - Chap 1 123 Density as a Conversion Factor can use density as a conversion factor between mass and volume!!
density of H2O = 1.0 g/mL \ 1.0 g H2O = 1 mL H2O
density of Pb = 11.3 g/cm3 \ 11.3 g Pb = 1 cm3 Pb
How much does 4.0 cm3 of lead weigh?
124. Example 1.10 What is the mass in kg of 173,231 L of jet fuel whose density is 0.738 g/mL?
125. Tro, Chemistry: A Molecular Approach - Chap 1 125 Order of Magnitude Estimations using scientific notation
focus on the exponent on 10
if the decimal part of the number is less than 5, just drop it
if the decimal part of the number is greater than 5, increase the exponent on 10 by 1
multiply by adding exponents, divide by subtracting exponents
126. Tro, Chemistry: A Molecular Approach - Chap 1 126 Estimate the Answer Suppose you count 1.2 x 105 atoms per second for a year. How many would you count?
127. Tro, Chemistry: A Molecular Approach - Chap 1 127 Problem Solving with Equations When solving a problem involves using an equation, the concept plan involves being given all the variables except the one you want to find
Solve the equation for the variable you wish to find, then substitute and compute
128. Tro, Chemistry: A Molecular Approach - Chap 1 128 Using Density in Calculations
129. Example 1.12 Find the density of a metal cylinder with mass 8.3 g, length 1.94 cm, and radius 0.55 cm
130. Tro, Chemistry: A Molecular Approach - Chap 1 130 Important Terms Chemistry
Experiment
Hypothesis
Natural Law
Scientific Method
Theory
Density
Measurement
Unit These are some of the important terms from the chapter. Make sure that you know their definitions and understand the relationships between them.These are some of the important terms from the chapter. Make sure that you know their definitions and understand the relationships between them.
131. Tro, Chemistry: A Molecular Approach - Chap 1 131 Homework You should examine and be able to answer all of the ‘Problems’…some of them (or similar questions) may be on the test
To be handed in for grading: 1.38, 1.42, 1.46, 1.48, 1.52, 1.58, 1.64, 1.72, 1.84, 1.92
Due date :
Home work for chapter 1 is :
Due date :Home work for chapter 1 is :
Due date :
