Density Making sure we KNOW what density is and how the density of air affects air pressure.

What is the formula for density? density = mass / volume density = mass ÷ volume density equals mass divided by volume

= ________ per ________ density (how crowded something is) how much mass (stuff) how much volume (space you fit it into)

Which is more dense? Why? The box on the right is more dense, because there is more mass (more molecules) crammed into the same volume.

Which is more dense? Why? The box on the left is more dense, because the same amount of mass (9 molecules of air) is crammed into a smaller volume.

Density changes with altitude More Less

Air pressure decreases when altitude increases

Heat up the air inside a balloon and… The molecules gain energy. They move around more. They take up more space, so the volume increases. Because the volume increases, density ________ decreases Lower density means the balloon will RISE.

3 ways to increase the density of air inside a balloon 2. Squeeze the balloon so that it has less volume. 1.Cool the air so that the molecules have less energy, move less, and therefore take up less volume. 3. Add more molecules so it has more mass.