What factors influence density?
Density: The amount of matter in a given space (Mass ÷ Volume).
Same mass, different volume
1. The box below contains a gas and has a mass of 2 grams. Draw what the gas molecules would
look like if the volume of the container were to increase from 20ml to 50ml.
= 1 gas molecules
2. Calculate the density of each box
Box 1
Box 2
Mass: 2 g
Volume: 20mL
Mass: 2g
Volume: 50ml
Box 1:
Box 2:
3. Conclusion- When the volume of a gas increases but the mass remains the same, the density will
INCREASE/DECREASE (circle one).
Same volume, different mass
1. The box below contains a gas with a mass of 2 grams. The volume of the box is 20ml. Suppose
more gas molecules are added to the container so that the new mass is 5 grams. Draw what the
molecules would look like.
2. Calculate the density of each box
= 1 gas molecules
Box 1
Mass: 2 g
Volume: 20ml
Box 2
Mass: 5 g
Volume: 20ml
Box 1:
Box 2:
3. Conclusion- When the mass of a gas increases but the volume remains the same, the density will
INCREASE/DECREASE (circle one).
When temperature changes
1. The syringe below contains a gas that, at a temperature of 23oC, has a mass of 2 grams and a
volume of 20ml. The gas was heated to 43oC. The new volume is 40ml. Draw what the molecules
might look like in the syringe. Be sure to draw the new location of the pump on the syringe.
2. Conclusion: When the temperature of a gas
increases, the volume will also increase
allowing the molecules to spread further
Syringe 1
Mass: 2 g
Volume: 20ml
Temp.: 23oC
apart. This causes an INCREASE/DECREASE
(circle one) in density.
Syringe 2
Mass: 2 g
Volume: 40ml
Temp: 43oC
v v v When pressure changes
1. The box 40ml below contains a gas with an initial mass of 2 grams. The pressure is then increased
from 100kPa to 120kPa. Draw what the gas molecules might look like in the container.
Box 1
Mass: 2g
Volume: 40ml
Pressure: 100kPa
v Box 2
Mass: 2g
Volume: 20ml
Pressure: 120kPa
Figure 1
v v 2. Look at Figure 1. What happens to air pressure as the
altitude increases?
3. According to Figure 1, what happens to the density of air
as the altitude increases?
http://www.visionlearning.com/en/library/Eart
h-Science/6/The-Composition-of-EarthsAtmosphere/107