why do things expand when heated
Objects expand when heated because the heat 'gives' molecules more energy, so they move around more.This vibration, as molecules are pushed further apart, is manifested as a larger volume. An exception is water, which contracts as it cools until you reach about 3.98 Â° C then starts to expand as it cools more.y heating the gas, you are adding energy to the particles, and as a result, they will move faster and with more force. If the gas does not have room to expand (set volume), t â¦ hen the pressure will increase because temperature and pressure vary directly.