1. Phase Changes

2. Phase Changes
Phase changes occur when substances move from one state of matter to another.
Ex: ice cube melting
This is a physical change.
Why is it not considered a chemical change?

3. Phase Changes
The Kinetic Theory helps explain how and why phase changes take place.
Gaining energy/heat  atoms move faster
Losing energy/heat  atoms slow down
When a substance condenses from a gas back to liquid, has it absorbed or released heat?

4. Phase Changes

5. Phase Change Graph

6. Properties of Matter

7. Properties of Matter Ways we describe matter Two categories: Physical
Chemical

8. Physical Properties Observed with your senses
Can be observed without changing the material
Examples:
Color
Shape
Density

9. Chemical Properties Cannot be observed without changing the matter
Describes how the matter reacts with other substances
Examples:
Flammability
Reactivity

10. Physical vs. Chemical Changes
Physical Changes
Chemical Changes
A change in size, shape, or state
No new substance is formed
Examples:
Tearing paper
Crushing a rock
Ice melting
A change in physical and chemical properties
A new substance is formed
Examples:
Burning paper
Frying an egg
Rusting

11. Signs of a Chemical Change
Chemical reactions either absorb or release energy.
Energy can be in many forms:
Heat
Light
Sound
Color
Bubbles

12. Density

13. Density Physical property
Density is the amount of matter (mass) compared to the amount of space (volume) the object takes up.

14. Density
Density is mass divided by volume
D = m/v
Our unit for density is g/ml or g/cm3

15. Density Formula Triangle

16. Water and Density
Since one gram of water has a volume of one mL, then the density of water will always be 1 g/mL.
50 mL of water will have a mass of 50 grams, so again the density of water will be 1 g/mL.
What would be the volume of 1000 mL of water? What would be the density?

17. Floating and Sinking
Less dense materials will float on top of more dense materials.
Objects with a density of less than 1 g/mL will float on top of water.
Objects with a density greater than 1 g/mL will sink in water.

18. Comparing Densities
Where is the most dense object?
Where is the least dense object?

19. Density Practice
What is the density of a 16 gram pencil with a volume of 8 cm3?
What is the volume of a substance that has a mass of 30 grams and a density of 3 g/mL?
What is the mass of 40 mL of milk if it has a density of 2 g/mL?