In a solid the particles are all really close together and stuck like that. As the solid melts and becomes a liquid the particles spread out. A solid won’t easily change its shape because the particles are bound together but in a liquid the shape is more fluid, take water when you pour it into a container it will change to fit the shape of a container this is because the particles aren’t as close and can move around. The particles of a solid change when it melts because it is changing states to a liquid.
