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

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/why were you able to smell the particles inside the balloon?

Kinetic Theory Matter is anything that has mass and takes up space. The kinetic theory describes how matter behaves. 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.

Density Density measures how closely the atoms or molecules are packed. Density is a physical property which is calculated by dividing mass by volume. The higher the density the more tightly packed the atoms are in a substance.

Density (continued) Density can help determine if a substance will float or sink in another substance. Higher temperature means higher volume (particles will spread out more) Higher volume means less density (particles aren’t as packed) Low density means the object is more likely to float. Ex: Water has a density of 1 g/mL. Anything with a density less than 1 will float in water.

Density Formulas The units of density are grams per cubic centimeter or grams per milliliter. units: _g_ or _g_ cm3 mL To find density: To find mass: To find volume:

Practice Density Problems A substance has a mass of 55 g and a volume of 11 cm3. What is the objects density? d=? m= 55 g v= 11 cm3 d =m/v d = 55 g / 11 cm3 d= 5 g/cm3

2. An object has a density of 7 g/cm3 and a volume of 8 cm3, what is the objects mass? d= 7 g/cm3 m=? v= 8 cm3 m = d v m = 7 g/cm3 x 8 cm3 m = 56 g

3. An object has a density of 5 g/cm3 and a mass of 25 g, what is the objects volume? d= 5 g/cm3 m= 25 g v= ? v= m/d v= 25 g / 5 g/cm3 v= 5 cm3