When do cells use oxygen to release energy

Why are graphs useful when interpreting data

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

The voltage applied across a given parallel-plate capacitor is doubled. how is the energy stored in the capacitor affected?