1. Classifying Matter 2.2

2. Pure Substances A pure substance is matter that always has exactly the same composition. A pure substance is matter that always has exactly the same composition. Pure substances are classified into two categories: elements and compounds Pure substances are classified into two categories: elements and compounds

3. Elements Element- a substance that cannot be broken down by ordinary means. Element- a substance that cannot be broken down by ordinary means. Atom- smallest part of an element still having the properties of that element. Atom- smallest part of an element still having the properties of that element. Examples: aluminum, gold, iodine Examples: aluminum, gold, iodine

4. Compounds Compound- 2 or more simpler substances combined chemically. Compound- 2 or more simpler substances combined chemically. Elements present are in specific ratios. Elements present are in specific ratios. Atoms are evenly distributed Atoms are evenly distributed Cannot be separated by ordinary means Cannot be separated by ordinary means Properties of compound differ from properties of simpler substances that make it up Properties of compound differ from properties of simpler substances that make it up Examples: Examples: H 2 O water H 2 O water NaCl salt NaCl salt

5. Mixtures A mixture is when two or more substances are physically combined. A mixture is when two or more substances are physically combined. Not set in specific ratios, not chemically bonded Not set in specific ratios, not chemically bonded Not evenly distributed Not evenly distributed Can be separated by ordinary means Can be separated by ordinary means Properties can vary because composition varies Properties can vary because composition varies Examples: pizza, salsa Examples: pizza, salsa

6. Two Categories of Mixtures Homogenous Mixture Homogenous Mixture Mixture looks the same throughout. Mixture looks the same throughout. Can’t see different parts. Can’t see different parts. Kool-aid, salt-water Kool-aid, salt-water Heterogeneous Mixture Mixture DOES NOT look the same throughout. Can see different parts. Mixed nuts, salad

7. 3 types of mixtures More specifically, there are 3 types of mixtures based on particle size. More specifically, there are 3 types of mixtures based on particle size. Solution Solution very small particles very small particles won’t separate into layers won’t separate into layers cannot be filtered cannot be filtered Ex: salt water Ex: salt water

8. Suspension Suspension large particles large particles separates into layers over time separates into layers over time can be filtered can be filtered Ex: Italian dressing. Ex: Italian dressing.

9. Colloid Colloid intermediate particles intermediate particles cannot be filtered cannot be filtered Ex: milk Ex: milk :