Speed is different from velocity because a. velocity has a direction
b. speed uses distance/time
c. velocity does not include time
d. velocity does not include distance

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