Chemistry I Mr. Crupi Colonial High School

1. Chemistry I Mr. CrupiColonial High School Unit: Matter- Properties and Change 2.1 - Properties of Matter 2.2- Changes in Matter 2.3- Mixtures of Matter 2.4- Elements and Compounds

2. Examining Matter • When examining matter, it helps to deal with pure substances • A pure substance is made up of only one type of matter • Elements are pure substances- they are made of only one kind of atom • Compounds are pure substances- they are made of one kind of molecule or formula unit

3. Examples: • Iron is a pure substance- made only of iron atoms • Sugar is a pure substance- composed only of sugar molecules • Air is not a pure substance- it is a mixture of different gases

4. Properties of Matter • Matter can be described by two kinds of properties: Physical Properties or Chemical Properties • Physical properties are observable without changing the composition of the substance • Chemical properties are only observable when the composition of the substance changes

5. Examples: • Color is a physical property • Flammability is a chemical property • Flexibility is a physical property • Reactivity with acids is a chemical property

6. More on properties • Physical and chemical properties can be either intensive or extensive • Intensive properties do not change depending on the amount of matter • Extensive properties change depending on the amount of matter

7. Examples: • Color is an intensive property • Mass is an extensive property • Volume is an extensive property • Reactivity with acids is an intensive property

8. Properties- More Examples

9. Matter can exist in three common states: • Solid- Matter with a definite shape and definite volume • Liquid- Matter with an indefinite shape but definite volume • Gas- Matter with an indefinite shape and volume • Liquids and Gases are fluids. (fluids flow) • Vapor is the gaseous state of a substance that is solid or liquid at room temperature

10. Solids/Liquids/Gases

11. Types of changes • Matter can undergo two types of changes- Physical changes or chemical changes • Physical changes do not change the composition of the substance • Chemical changes change the composition of a substance

12. Examples • Burning is a chemical change • Melting is a physical change • Shattering a glass is a physical change • Reacting with acid is a chemical change

13. The Law of conservation of mass • All matter obeys the law of conservation of mass • The law of conservation of mass states that in a chemical or physical change, matter is neither created nor destroyed

14. The law of conservation of mass

15. Some sample problems • If 14.0 grams of Nitrogen are reacted with 3.0 grams of Hydrogen to form ammonia, calculate the mass of ammonia 14 g N + 3 g H = 17 g ammonia • If 16.0 grams of Oxygen are reacted with Carbon to form 22.0 grams of Carbon Dioxide, calculate the mass of Carbon used 16.0 g O + x g C = 22.0 g CO2 C = 6.0 g

16. Mixtures • Matter is rarely found as pure substances. More often than not, it is in a mixture • Mixtures are combinations of two or more substances in which each substance retains its chemical properties. Can be separated physically.

17. Types of Mixtures • There are two types of mixtures: • Homogeneous mixtures- mixtures with constant composition throughout • Heterogeneous mixtures- One without a constant composition throughout.

18. Examples of Homogeneous mixtures • Kool-Aid • Tap Water • Gasoline • Homogeneous mixtures are also called solutions

19. Examples of Heterogeneous Mixtures • Pizza • Muddy Water • A Rat

20. Separating Mixtures • There are various ways to separate mixtures • Colored candies could be separated manually

21. Separating Mixtures • Mixtures of solids in liquids can be filtered

22. Separating Mixtures • Mixtures of liquids in liquids can be distilled • Distillation involves boiling away one of the liquids • Crystallization separates solids that are dissolved in liquids • Chromatography separates dissolved substances by their mobility

23. Elements • An Element is a pure substance that cannot be separated into simpler substances by physical or chemical means • All of the known elements are listed on the periodic table

24. Periodic Table

25. Periodic Table

26. Compounds • Elements combine with each other chemically to form compounds • A compound is a combination of two or more different elements combined chemically

27. Examples • Sodium chloride: NaCl is a compound made of 1 sodium atom and 1 chlorine atom • Calcium Carbonate: CaCO3 is a compound made of 1 calcium atom, 1 carbon atom, and 3 oxygen atoms • How many of each atom are in Aluminum sulfate: Al2(SO4)3?

28. The Law of Definite Proportions • All compounds obey the law of definite proportions • The law of definite proportions states that a compound, no matter how much of it you have, always has the same ratio of elements composing it.

29. The Law of Definite Proportions • If samples of matter have different ratios of elements, they are different compounds • To calculate the percent by mass of an element in a compound, you use the following formula:

30. Example • Calculate the percent by mass of each element in aluminum chloride, AlCl3

31. The Law of multiple proportions The law of multiple proportions states that when elements form compounds, they always combine in simple whole number ratios Example: H2O (Water): 2 hydrogens to 1 oxygen H2O2(Hydrogen Peroxide) 2 hydrogens to 2 oxygens