Describing Substances Based on Physical Properties

1. Date: 8/28/2018 Unit 1: Chemistry Learning Goal: Describe substances based on their physical properties.   Investigative Science - Ms. Kohler Warm up:What happens to the energy of matter as we move from a solid state to a gaseous state? No, you DO NOT have a reflection today!

2. Date: 8/28/2018 Unit1: Chemistry Learning Goal: Describe substances based on their physical properties.  Investigative Science - Ms. Kohler Pure substances, continuedCompounds are pure substances • Pure substances that are not elements are compounds. Compounds are composed of more than one kind of atom. • example: carbon dioxide (CO2) • There may be easier ways of preparing them, but compounds can be made from their elements.  • Compounds can be broken down into their elements, though often with great difficulty.

3. Date: 8/28/2018 Unit1: Chemistry Learning Goal: Describe substances based on their physical properties.  Investigative Science - Ms. Kohler Mixtures • A mixture is a combination of two or more substances that are not chemically combined. • Air is a mixture of mostly nitrogen and oxygen.  • All the different gases in air are physically mixed. • The proportions of the gases can vary. • Water is not a mixture. • The H and O atoms are chemically bonded • The ratio of H to O atoms is always 2 to 1.

4. Date: 8/28/2018 Unit1: Chemistry Learning Goal: Describe substances based on their physical properties.  Investigative Science - Ms. Kohler Mixtures, continuedmixtures can vary in composition and  Properties • The proportion of the materials in a mixture can change.  • The properties of the mixture may vary. • An alloy is a solid mixture.  • example: An alloy of gold and other metal atoms is stronger than pure gold. • 18-karat gold contains 18 grams of gold per24 grams of alloy. • 14-karat gold contains 14 grams of gold per24 grams of alloy.

5. Date: 8/28/2018 Unit1: Chemistry Learning Goal: Describe substances based on their physical properties.  Investigative Science - Ms. Kohler PARTICLE MODELS FOR GOLD AND GOLD ALLOY  • A property of pure gold that is NOT desirable is that it is very soft and bends easily – gold jewelry is an alloy (mixture) of silver and copper to give it strength so it does not wear out or become misshapen.

6. Date: 8/28/2018 Unit1: Chemistry Learning Goal: Describe substances based on their physical properties.  Investigative Science - Ms. Kohler MIXTURES, CONTINUED: HOMOGENEOUS MIXTURES • A homogeneous mixture describes something that has uniform structure or composition throughout. •   examples: gasoline, syrup, and air • Because any two samples of a homogenous mixture will have the same proportions of ingredients, homogenous mixtures have the same properties throughout.

7. Date: 8/28/2018 Unit1: Chemistry Learning Goal: Describe substances based on their physical properties.  Investigative Science - Ms. Kohler MIXTURES, CONTINUED: HeteroGENEOUS MIXTURES • A heterogeneous mixture describes something that is composed of dissimilar components. • example: A mixture of sand and water is a heterogeneous mixture. • Any two samples of a heterogeneous mixture will have different proportions of ingredients. • Heterogeneous mixtures have different properties throughout.

8. Date: 8/28/2018 Unit1: Chemistry Learning Goal: Describe substances based on their physical properties.  Investigative Science - Ms. Kohler Examples of mixtures • Mixtures can be either homogeneous or heterogeneous

9. Date: 8/28/2018 Unit1: Chemistry Learning Goal: Describe substances based on their physical properties.  Investigative Science - Ms. Kohler Classifying matter