Describe what happens to the particles of a solid, in terms of movement and kinetic energy, as it is heated to its melting point, including whether this is a physical or chemical change.

- In a solid, atoms (or molecules) are bond together, so they cannot move freely but they can only vibrate around their fixed position.

- As the solid is heated, more energy is provided to the atoms (molecules), so they begin vibrating faster and faster as the solid is heated

- When the temperature of the solid reaches the melting point, the atoms (molecules) are vibrating fast enough to break the bonds between each other. During this phase, the temperature of the solid does not increase, because all the energy provided is used to break the molecular bonds

- When all the bonds are broken, particles are free to move, so the solid has turned into a liquid

This process (melting of a solid substance) is a physical change, not a chemical change, because the chemical composition of the substance does not change, but only the form of the substance changes.