Hink about the friction activity. return to this activity to see it again if you need to. explain what happened in each of the two demonstrations, and then compare them. use the terms resistance, vacuum, gravity, velocity, and friction.

The freezing and boiling point of a substance changes as the air pressure around it changes. for example, at a lower air pressure (higher altitude) it is easier for water molecules to escape from liquid into the air. in a high altitude city such as denver, colorado compared to a sea-level city such as houston, texas, water