1. Describing Matter To describe matter we use properties! Property- a way to describe matter, a characteristic 2 types: Physical Chemical

2. Describing Matter Physical property- a way to describe matter using your senses, it can be observed or measured without changing the identity of the matter Example: you do not need to change an apple if you see that it is red

3. Describing Matter You use physical properties all the time!! Examples: Determine if your socks are clean by odor Determine if you can fit all your books in your backpack by volume Determine if your shirt matches your pants by color

4. Physical Properties Physical PropertyDefinitionExample State or phaseThe ability to transfer thermal energy from one area to another Ice is a solid form of water. DensityMass per unit volumeLead is used to make sinkers for fishing line because lead is more dense than water. Thermal ConductivityThe ability to transfer heatPlastic foam is a poor conductor, so hot chocolate in a plastic foam cup will not burn your hand. DuctilityThe ability to be drawn into a wire Copper is often used to make wiring. MalleabilityThe ability to be pounded into thin sheets Aluminum can be rolled or pounded into sheets to make foil. SolubilityThe ability to dissolve in another substance Sand does not dissolve in water.

5. Physical Properties: Density Density= the amount of matter in a given space Density= mass = m volume v Units for density are g/cm3, g/mL, kg/m3, kg/L **MEMORIZE: Liquid water has a density of 1.0 g/cm3.

6. Describing Matter Chemical Property- a way to describe matter based on its ability to undergo a chemical change Example: a piece of wood can be burned to create new substances with properties different from the original piece of wood *****Chemical properties can be observed but aren’t always as easy to observe as physical properties.

7. Chemical Properties Chemical PropertyDefinition FlammableThe ability to burn ReactiveWhen 2 substances get together, something can happen

8. Physical VS Chemical Properties SubstancePhysical PropertyChemical Property HeliumLess dense than airNon-flammable WoodGrainy textureFlammable Baking SodaWhite powderReacts with vinegar to produce bubbles Powdered SugarWhite powderDoes NOT react with vinegar Rubbing AlcoholClear liquidFlammable Red Food ColoringRed colorReacts with bleach and loses its color IronMalleableReacts with oxygen (O)

9. Physical Changes Physical change- affects one or more physical properties of a substance Example: breaking chalk- you change its size and shape BUT no matter how many times you break it is still chalk, NO CHEMICAL PROPERTIES CHANGE.

10. Physical Changes Examples More examples of physical changes Freezing water for ice cubes Sanding a piece of wood Cutting your hair Crushing an aluminum can Bending a paper clip Mixing oil and vinegar Breaking a paper towel

11. Can physical changes be undone? Yes! They don’t change the identity of a substance

12. Chemical Changes Chemical change- occurs when 1 or more substances are changed into entirely new substances with different properties Example: baking a cake

13. Chemical Changes Examples More examples of chemical changes Soured milk- bacteria forms new substances in milk Hot gas- forms when hydrogen and oxygen join to make water during a space shuttle launch Effervescent tablets- bubble when baking soda reacts with water Statue of liberty- the shiny, orange-brown copper reacts with carbon dioxide in the air and rusts creating a green looking statue of liberty

14. Can chemical changes be undone? Mostly, NO! Why? Because new substances are formed You cannot reverse chemical changes Only some chemical changes can be reversed under the right conditions Can you un-bake a cake or turn milk un-sour? NO!

15. Questions: Classify each of the following properties as either physical or chemical: Reacts with water Dissolves in acetone Is blue Does not react with hydrogen peroxide What is the difference between physical changes and chemical changes?

16. Test Bonus Question (+1 point): A block of wood has a length of 3 cm, a width of 1 cm, and a height of 2 cm. It has a mass of 12 g. What is the block of woods density?