How does a comet change when it comes close to the sun

It loses mass. The comet speeds up, this is because higher gravity = higher speed, also the ices of water, methane, and ammonia vaporize because of the heat, this creates dust and jets of gases. These gases and the dust form a cloud called a com

A comet is like a giant dirty snowball, the size of a town or city. It is made of ice, dust, and small pieces of rock. As a comet gets closer to the Sun, it starts to melt. It becomes surrounded by lots of gas and dust.