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Physical Science is the study of matter and energy . It is broken into two main sciences, physics and chemistry. Chemistry- studies the forms of matter and how it interacts and changes. Physics- studies energy and how it affects matter. What is matter?.
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Physical Science is the study of matter and energy. It is broken into two main sciences, physics and chemistry Chemistry- studies the forms of matter and how it interacts and changes Physics- studies energy and how it affects matter
What is matter? Matter is anything that has mass and takes up space Matter has mass and volume Mass-the amount of matter in an object Volume-the amount of space occupied by an object How is mass measured? How is volume measured? Mass is measured using a balance Volume is measured using a meter stick and calculations or a graduated cylinder
Volume How do you find the volume of a regular shaped object? (Length)(Width)(Height) = Volume How do you find the volume of an irregular shaped object? Place it in a graduated cylinder and observe the change in water level. 1mL = 1 cm³
Mass Mass is also known as the measure of inertia Inertia- tendency of an object to resist a change in its state of motion Mass is not the same thing as weight! Weight- measure of gravitational force exerted on an object Your weight is different on the Moon than on Earth, but your mass is the same. Mass -constant, no matter where in the universe the object is -measured using a balance and expressed in grams Weight -Varies, depending on where the object is in the universe -measured using a spring scale and expressed in newtons (unit of force)
Practice using a balance and a spring scale. Remember that the units are different!
How do we distinguish one example of matter from another? Physical Properties of Matter A Physical Property is something that can be observed or measured without changing the matter’s identity. -They help you identify a substance Examples: Conductivity- ability to transfer heat or electricity State- solid, liquid, or gas Density- mass per unity volume of a substance Solubility- ability to dissolve in another substance Ductility- ability to bend (be pulled into wire) Malleability- ability to be flattened without breaking Color- wavelengths of light reflected by the substance Hardness-resistance to bending, stretching, or flattening
Density- describes the ratio of mass to volume. i.e. dense objects have a lot of mass squeezed into a small volume Density tells you what will float and what will sink. -If one object is less dense than another, it will float above it. e.g. oil and water -Why do boats float? Boats float because the overall density of the boat (including the air inside of it) is less than the density of water.
Density = Mass/Volume The units for density coincide with the equation (g/cm³ or g/mL) The density of water is 1 g/mL Anything with a density greater than one sinks. Anything with a density less than 1 floats. M ÷ ÷ X V D
Why does density determine floating and sinking? -Force of gravity (weight) increases with mass -Buoyancy Force is equal to the volume of the liquid displaced Basically, the denser the object the greater the force of gravity and the weaker the buoyancy force. If gravity is stronger it sinks. If buoyancy is stronger it floats.
Physical Changes- change of matter from one form to another that does not involve a chemical change. -You manipulate one of its physical properties but do not transform it into a new substance Examples include: -Melting -Freezing -Vaporization -Stretching -Smashing -sometimes mixing Physical changes can be undone by physical means (reshaping, adding heat etc.)
States of Matter There are three main states of matter, Solids, Liquid, and Gas. -A fourth, plasma, also exists but under rarer circumstances on Earth Which state matter is in depends on the energy of the molecules and the degree of entropy. Entropy- disorder or lack of organizational structure between molecules -Entropy usually increases as energy increases -High entropy means matter cannon take a definite shape, low entropy allows for a definite shape What is easier to control, a group of tired, well-behaved kids or a group of sugar-high, hyper kids?
Solids • low entropy • definite shape • definite volume • usually low energy/temperature Crystalline- orderly arrangement of particles Amorphous-particles arranged in no specific pattern
Liquid • Higher entropy • Indefinite shape (conforms to container) • Definite volume • Higher energy/temperature Surface Tensions- how strong particles at the surface of a liquid cling to each other. Viscosity- how much a liquid’s molecules cling to each other and their surroundings. -resistance to flow
Gas • High Entropy • Indefinite shape • Indefinite volume (fills all available space) • High energy/temperature Volume, and resultantly pressure on surrounding matter, increases as energy/temperature increases
Matter moves from one state to another by adding energy. The amount of kinetic energy in a molecule (how much it is vibrating in place) is its temperature. So…adding or losing heat causes matter to move from one state to another
How much energy a type of matter needs to change states is a physical property -liquid water can only exist between 0 and 100° Celsius, above that it changes to gas, below that it changes to ice Each state change has a name… Solid to liquid- melting Liquid to gas- vaporization/evaporation Gas to liquid- condensation Liquid to solid- freezing Solid to gas- sublimation
What about Plasma? Plasma is similar to gas in that he has no definite shape or volume, but its particles are electrically charged or ionized. It carries so much energy that atoms are missing particles, leaving some with a positive charge and others with a negative charge Since it is ionized, it reacts to magnetism and can be directed Because of the overwhelming mass of stars, plasma makes up most of the matter in the universe Common examples of plasma… -Lighting -Stars -Flames -fluorescent lamps -neon displays -plasma TVs
Chemical Properties tell us which chemical changes will take place under certain conditions. Chemical Change-When one or more substances transform into one or more new substances with different properties Chemical changes take place everywhere. Brainstorm a few examples…
Chemical Properties and Changes Chemical Properties- characteristics of matter based on its ability to transform into a new form of matter, to change from one substance to another. e.g. flammability and reactivity They can also be used to classify substances, but they are harder to observe or measure than physical properties Flammability is a substance’s ability to burn Reactivity is a substance’s ability to combine with other substances to form new substances e.g. rusting, acid base reactions
How do we know when a chemical change has taken place? Often the appearance (texture, color, physical state) can change. Other signs of change include… -heat -odor -fizzing and foaming -sound -light Unlike physical changes, chemical changes are hard to reverse -You can undo some reactions by chemical means, but most of the time it is difficult
Elements, Compounds, and Mixtures We can describe matter based on its physical and chemical properties, but how do we organize it? Pure substances- any form of matter made of uniform particles Mixture- matter made of multiple types of particles that are not chemically bound
Pure substances are split into two categories… Elements- pure substance made up of only one type of atom -cannot be broken down into simpler substances by physical or chemical means Compounds- pure substance made up of multiple types of atoms, chemically bound to form particles called molecules
Elements are all made up of different types of atoms and organized according to their physical and chemical properties on the periodic table.
The three main groups are metals, nonmetals, and metalloids Metals- shiny, malleable, conductive (to heat and electricity) Nonmetals- dull, nonconductive, usually brittle (often are gases or liquids at room temperature) Metalloids- share properties of both metals and nonmetals Number of protons and electrons, atomic mass, electronegativity, and polarity also affect where an element falls on the periodic table. Based on an element’s position on the periodic table and the properties of the elements around it you can usually predict its properties
Compounds Compounds are made of chemically bound elements, but their properties can be different than the properties of the elements that make them. dangerous elements can make harmless compounds and vice versa A type of molecule is always made up of the same ratio of its component elements Examples- water is always 2 Hydrogen atoms and 1 oxygen -table salt is always 1 sodium atom and 1 chlorine atom
Compounds can be broken down during a chemical change. -Sometimes they need a catalyst, sometimes they need an input of energy, and sometimes they just degrade over time. Eat a steak, its proteins are broken down into amino acids (mechanical and chemical digestion) then your body reassembles the amino acids into other proteins (translation). Can you come up with any other examples of compound breaking down or being formed? Glucose Deoxyribonucleic acid
Mixtures You have a mixture when two or more pure substances are blended together with no particular ratio between the amounts of each substance. Unlike compounds, they can be separated using only physical means -distillation (boiling) -centrifuging (spinning) Mixtures are categorized by how well they are mixed…
There are three main types of mixtures, solutions, suspensions, and colloids. Solutions- mixed so well that they look like a single substance -they have two parts, the solute or substance being dissolved and the solvent or the substance in which the solute is dissolved examples… Suspensions- particles of the added material are large enough that they eventually settle to the bottom of the mixture. examples… Colloids- particles are evenly distributed throughout, large enough to see, but not large enough to settle to the bottom -If you shine a light through them they block some of the light. examples…
Atoms: Theory and Structure Atoms are the smallest unit of an element Each element is made-up of a different type of atom, distinguished by the number of the different subatomic particles that compose them. There are three subatomic particles that make-up an atom Proton: + charge and large mass (1amu) Neutron: 0 charge and large mass (1amu) Electron: - charge and small mass Protons and neutrons are found in the nucleus of the atom and electrons orbit around it, in what is called the electron cloud.
John Dalton (late 1700’s)- after observing that elements combine in certain proportions to create compounds and experimenting to test his theory, he published his atomic theory. • All substances are made of atoms. Atoms are small particles that cannot be created, divided, or destroyed. • Atoms of the same element are exactly alike, and atoms of different elements are different • Atoms join with other atoms to form new substances He was close, but later research required a few changes.
1897- John Thomson discovered that atoms had negatively charged particles inside them (electrons). 1909- Ernest Rutherford discovered that atoms had to be mostly dead space with (-)electrons distantly surrounding a dense (+)nucleus. 1913- Niels Bohr proposed that electrons orbit the nucleus at varying energy levels. Modern theory states that the paths of an electron cannot definitively be predicted -electrons roughly move in patterns called orbitals which coincide with their energy level, but their exact position cannot be determined.
All atoms of a particular element have the same number of protons in their nucleus, but the number of neutrons can vary. Carbon-12 Stable The different versions of an element are called isotopes -some isotopes are radioactive, which means they decay over time
Atomic Mass Unit (amu)- approximate mass of one proton or neutron Mass Number- number of protons and neutrons in an atom Atomic Mass- weighted average mass of the varying isotopes of an element Chlorine-35 makes up 76% of all chlorine in nature Chlorine-37 makes up the other 24% How do we find the atomic mass?
How can we revise Dalton’s Theory? • All substances are made of atoms, which in turn are made of smaller particles called electrons, protons, and neutrons. • They can be divided or combined (difficultly)- nuclear fusion and fission • Atoms of the same element will all have the same number of protons and electrons, but the number of neutrons and as a result the mass may vary (isotopes). • Atoms do join with other atoms to form new substances (compounds)
Chlorine: (35) (0.76) = 26.60 (37)(0.24) = 8.88 8.88 + 26.60 = 35.48 amu Try a few… Boron-10 = 20% Boron-11 = 80% Atomic mass = Silicon-28 = 92% Silicon-29 = 5% Silicon-30 =3% Atomic mass=
Color Quiz • An atom is the base unit of a(n)… • Black- element -Orange-compound • Can you identify the exact position of an electron? • Black- yes -Orange- no • The weighted average mass of an element’s isotopes is its… • Black- mass number -Orange- atomic mass • Who first attempted to describe atomic theory? • Black- John Dalton -Orange- Ernest Rutherford • What takes up the most an atom’s volume? • Black- nucleus -Orange-Electron Cloud
Periodic Table of Elements A table that organizes the elements according to their physical and chemical properties. An element’s position on the table, relative to those around it, makes it possible to predict its properties -atomic mass, melting temperature, electronegativity, polarity, etc.
The periodic table is laid out in groups (vertical columns) and periods (horizontal rows) The number of valence electrons increases as you move from left to right, so elements on the left are the most positively charged and elements on the right are the most negatively charged. Groups 1-13 are positive Group 14 is +/- Groups 15-18 are negative
What are valence electrons? Valence electrons are electrons in the outermost shell (energy level) of an atom and are the ones involved in reacting with other atoms -they can either be transferred to or shared with another atom in forming a compound A full shell (energy level) has 8 electrons, atoms react with other atoms to try to fill their outer shell. -Hydrogen and Helium only need 2 for a full shell If you have 1 valence electron, is it easier to give away that electron or to get 7 more?
Important Metals sections- • Alkali metals-highly reactive • Alkaline Earth metals • Transition metals • Lanthanides • Actinides- all radioactive (decay over time) • Important nonmetal sections- • Noble Gases- nonreactive • Halogens- highly reactive, bind with metals to form salt • Other elements- • Elements between groups 13-16 can be reactive, but they usually bond covalently rather than ionically
Different periodic tables provide you with different information about each element, but they all at the least give you… • Atomic number • Atomic mass • Element symbol Some element symbols are based on the element’s Latin names. Ferrum = Iron Aurum = Gold
What are chemical reactions/changes? How do we know when one has happened? Why do they happen? Are atoms ever created or destroyed during chemical reactions?
Signs of Chemical Reactions Chemical reactions often give us physical evidence to know that a reaction is taking place. Such as… Color change Precipitate formation (forming a solid) Gas release (creating a gas) Heat (energy release)
Compounds are represented using chemical formulas (e.g. H2O) and chemical reactions are represented using chemical equations. Chemical equations tell you the chemical formulas of all of the compounds involved and how many of each compound is involved. We know… -the number of each compound -The kinds of atoms involved -the number of each kind of atom The compounds entering the reaction are called reactants The compounds produced in the reaction are called products
The one BIG rule The atoms in the reactants much equal the atoms in the products The Law of Conservation of Mass -Mass (matter) is neither created nor destroyed during a normal chemical or physical reaction As a result the atoms present before a reaction must also be present after a reaction
To balance equations and make sure that no matter is lost or created, we use coefficients. -they tell us how many of a particular compound is involved in a reaction -By adding them to one, two, or all of the compounds involved in a reaction we can be sure that the same number of atoms enter and leave a reaction. CO2 + H2O C6H12O6 + O2 6CO2 + 6H2O C6H12O6 + 6O2 Balancing chemical equations is part of a branch of chemistry called Stoichiometry http://education.jlab.org/elementbalancing/index.html
