As the air molecules move through the valve they have friction as they hit the walls, and its this friction that causes it to heat up.
<u>Answer:</u>
All living things are not made of cells.
The subatomic particle involved in chemical bonding is the electron. Electrons are the smallest of all subatomic particles and orbit the nucleus in discrete energy levels called shells. Electrons are negatively charged and the nucleus is positively charged due to the protons.
