Solids micro-lesson

Solids are one of the three states of matter. And the two key properties of solids that you need to remember are they have a fixed weight or volume, and they keep their shape. Look around you right now. You're going to see lots of solid objects. Most things that you can pick up and hold in your hands will be solid. So, solids cannot flow and they do not take the shape of their container. For example, my sunglasses are a solid. When I put them in their case, they stay the exact same size, the exact same shape, and the exact same weight. And solids also will not expand to fill the volume of their containers so when I put them in the case, they do not fill the entire case up. Now, the reason solids do not change shape is because of the particles in solids. They're arranged really close together and they're held in place by really strong forces called bonds. Now, these particles can vibrate but they do not move around so solids do not change shape without external forces. Paper is a solid. Yes, it bends but it only bends when I'm pushing or pulling or bending it with external force. So, some examples of solids are bricks, wood, glass, plastic, rocks, paper, flowers and most metal. But what about Play-Doh? So, Play-Doh is a very interesting solid which we call an amorphous solid. Yes, it does change shape but it only changes shape when you manipulate it, when you use external forces. So, solids have a fixed weight and volume and they keep their shape.