What holds the particles together

If a stick of chalk is really a crowd of separate tiny particles, what holds them together as one solid stick?

The constituent particles of matter pull on each other. These attractive forces are called interparticle attractions.

How strong they are depends on two things:

• the substance itself: different materials hold their own particles with different strengths;
• the distance between the particles: even a slight increase in distance makes the attraction drastically weaker.

The strength of these attractions is what decides whether a substance is a solid, a liquid or a gas. The rest of the chapter looks at each state with exactly this idea.

People have wondered how far matter can be broken down since ancient times. Acharya Kanad, an ancient Indian philosopher, was the first to speak of the Parmanu, an atom. He believed matter is made of tiny, indivisible, everlasting particles called Parmanu, and he wrote about it in the Vaisheshika Sutras.