1. Kinetic Theory and Density Ch. 3 pg. 74-75

2. Balloon Demo Pass around the balloon and sniff it. What do you think is in the balloon? (Don’t shout it out!) Are the particles inside the balloon matter? How do you know? How were you able to smell the particles inside the balloon?

3. Kinetic Theory The kinetic theory describes how matter behaves and the differences between solids, liquids, and gases. There are 3 main points to the theory: –1. All matter is made up of atoms and molecules that act as tiny particles. –2. All particles are in motion. The higher the temperature, the faster they move. –3. At the same temperature, heavier (more massive) particles will move more slowly.

4. Density Density measures how closely the atoms or molecules are packed. Density is a physical property which is calculated by dividing mass by volume. –Density is an intensive property because it is determined by the kind of matter in an object The higher the density the more tightly packed the atoms are. –Which has the highest density, a sold, liquid, or gas? –Answer: solid

5. Density (continued) Density can help determine if a substance will float or sink in another substance. –The volume of most substances increases as the temperature increases, however the mass stays the same. The density of a substance will decrease as the temperature increases The units of density are grams per cubic centimeter or grams per milliliter. units: _g_ or _g_ cm 3 mL

6. Density Formulas To find density: To find mass: To find volume:

7. Buoyancy Buoyancy occurs when a more dense substance pushes a less dense substance upwards to floating.

8. Practice Density Problems 1.A substance has a mass of 55 g and a volume of 11 cm 3. What is the objects density? d=? m= 55 g v= 11 cm 3 d =m/v d = 55 g / 11 cm 3 d= 5 g/cm 3

9. 2. An object has a density of 7 g/cm 3 and a volume of 8 cm 3, what is the objects mass? d= 7 g/cm 3 m=? v= 8 cm 3 m = d v m = 7 g/cm 3 x 8 cm 3 m = 56 g

10. 3. An object has a density of 5 g/cm 3 and a mass of 25 g, what is the objects volume? d= 5 g/cm 3 m= 25 g v= ? v= m/d v= 25 g / 5 g/cm 3 v= 5 cm 3