The Nature of Matter
The particulate nature of matter
Explain the three states of matter by how tightly their particles are held and how much space sits between them.
Break a stick of chalk, break the pieces, grind what is left in a mortar and look at the powder through a magnifying glass. Each speck is still chalk. Keep going in your imagination and you reach units that cannot be broken any further — the constituent particles the chalk was built from.
Particles, and what holds them
Matter is made of a great many extremely small particles, too small to see even through an ordinary microscope. They are held together by attractive forces called interparticle attractions, and the gaps left between them are called interparticle spaces. How strong those attractions are is what decides whether a substance is a solid, a liquid or a gas.
Worked example
Two teaspoons of sugar are stirred into a glass of water. The water level rises when the sugar goes in, then drops back a little once it has dissolved. Why?
Before stirring, the sugar grains sit on top of the water and take up room of their own, so the level goes up.
At this point nothing has dissolved. The grains are behaving like any insoluble solid dropped in, such as sand.
Try it together
A syringe with no needle is filled with air, its open end blocked with a thumb, and the plunger pushed in.
A short answer is enough each time.
1.Does the volume of the air inside the syringe increase, decrease or stay the same?
Have a go
Have a go on your own. The temperature at which a solid melts to become a liquid, at atmospheric pressure, has a two-word name. What is it?
Ready to practise?
Eight questions on what you have just read. Nothing is timed, and you can play as many times as you like.