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WELCOME TO CHEMISTRY

WELCOME TO CHEMISTRY. With Dr. Wieser. Chapter 1 Section 1. Chemistry can be defined as the study of matter. Matter is anything that has mass and occupies space. So chemistry is the study of pretty much everything.

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WELCOME TO CHEMISTRY

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  1. WELCOME TO CHEMISTRY With Dr. Wieser

  2. Chapter 1 Section 1 • Chemistry can be defined as the study of matter. • Matter is anything that has mass and occupies space. So chemistry is the study of pretty much everything. • We will focus on the structure of matter and the changes that matter can undergo.

  3. A chemical is defined as any substance that has a definite composition. • Look around the room-how many chemicals can you observe? • There are many different branches of Chemistry. See p4. • Also on PP4-5-different types of research are discussed.

  4. Section 2 Matter & Its Properties • We can define matter as anything that has mass and occupies space. All matter is composed of atoms. Elements and compounds are made up of atoms. • An atom is the smallest unit of an element that has the properties of that element. An element is a pure substance and can not be broken down into simpler substances.

  5. A compound is a pure substance that is made of two or more elements that can be broken down into simpler substances.

  6. Matter can exist in four states (three are found on Earth) • Solid • Liquid • Gas • Plasma (found in the interior of the sun)

  7. Note that energy must be supplied to go from one state or phase to another: • Solid →liquid→gas • Solids-have fixed volume and shape. • Liquids-have fixed volume but take on the shape of their container. • Gases-have neither fixed volume or shape.

  8. In addition to phase changes matter can undergo other physical changes: • Physical changes do not produce any new substances: • What happens to an ice cube when heat is supplied? • What about when sugar is dissolved in water?

  9. Chemical changes produce new substances. • In a chemical reaction one or more substances, the reactants are converted to one or more new substances, the products.

  10. A physical property is one that describes a physical change. When considering phase changes, the melting point of a substance is a physical property. In the case of ice, this temperature is______oC. • A chemical property describes the chemical change. Paper undergoes a chemical change when it burns, so the ability to react with oxygen is a chemical property of paper.

  11. Compounds and elements are both pure substances. • Compounds are a chemical combination of two or more elements. • Mixtures are a physical combination of two or more pure substances. • Mixtures that are uniform in composition are called homogenous mixtures (sugar in water) • Mixtures that are not uniform are heterogeneous mixtures (sand in water)

  12. End of Section 2 • Homework: always due at the beginning of the next class period. • P 14 #’s 1-2-4 • And p22 #’s 10-12

  13. Section 3 Elements • I mentioned previously that elements are composed of atoms. The periodic table lists all the known chemical elements. • The columns are called groups or families –there are 18 of them. • The rows are called periods. (see p 17). • There are three types of elements shown on the table.

  14. Metals • Non-metals • Metaloids or semi-metals • Pages 18-20 give examples. • Homework for section 3 • Page 20 #’s 1-4 • END of Chapter 1 a test will follow.

  15. The Scientific Method • Observation • Hypothesis • Observation or experiment • Theory • Observation or experiment • Law • See page 31

  16. Scientists ask questions and make observations. • A hypothesis is a possible explanation for an observation. A hypothesis must be testable-usually by performing an experiment and analyzing the result.

  17. Experiments are conducted under controlled conditions. • If the results of an experiment may support the hypothesis- which will lead to more experiments or not support it-then you need to look for a new hypothesis or the result may lead you in a whole new direction. • If over a relatively long period of time many experiments support the hypothesis then the hypothesis can become a theory.

  18. A theory is the best current explanation for a series of observations. If new information becomes available in the future then the theory may be modified or even replaced. This is all part of the scientific method! • In the course of performing experiments, sometimes a cause and effect relationship is observed.

  19. This relationship is a scientific law-scientific laws do not explain observations but point out connections between observations. For example later in the year we will study the Gas Laws-one says that when the temperature of a gas goes up so does its volume-the theory that explains this observation is called the Kinetic Theory of gases.

  20. Chapter 2 • One of the key parts of the scientific method is the ability to make measurements. • If I told you a measurement was 59.7. What would be your response?

  21. The metric system is the one used in science. The units are called SI units-we will see that not all the units we will use are SI units. • SI base units are listed on p 34.

  22. Some for you to try: • a. 1.34 g to kg • b. 15.2 cm to m • c. 2580. mg to kg

  23. Derived units: many measurements use more complicated units derived from the base units. For example volume (l x w x h) requires a cubic unit, if the measurements were in meters the unit would be m3. • The non-SI unit we commonly use for volume is the liter which is equivalent to a dm3 or 1000 cm3 (1000 mL)

  24. One important physical property of matter is density . • Density = mass/volume • Every substance has its own unique density. • See p 17 for a list. • Since the density formula has 3 variables, 3 types of problems are possible.

  25. 1. given mass and volume-find density • a substance has a mass of 23.2 grams and a volume of 18.5 cm3. Find its density. • 2. given density and volume, find mass (g) • D = m/V so m=D x V • The density of silver is 10.5 g/cm3. Find the mass of a block of silver with a volume of 40.0cm3.

  26. 3. Given the density and mass, find the volume of a substance. • D= m/V so V= m/D • Find the volume of a piece of iron that has a mass of 147grams. (from p 17 density of iron = 7.86 g/cm3)

  27. Chapter 1 Section 3 • Substances (pure) • - matter in which all samples have identical composition and properties. • Elements • substances that cannot be decomposed into simpler substances via chemical reactions • Elemental symbols • found on periodic chart

  28. Compounds • substances composed of two or more elements in a definite ratio by mass • can be decomposed into the constituent elements • Water is a compound that can be decomposed into simpler substances – hydrogen and oxygen

  29. The properties(chemical and physical) of compounds are unique and are totally different from the elements that make up the compound. • Sodium chloride for example. • NaCl

  30. Mixtures • composed of two or more substances • homogeneous mixtures • heterogeneous mixtures

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