A solid is like your favorite toy block. When you hold it, you can feel that it’s hard and it doesn’t change its shape. It stays the same whether you push it or pull it. Solids have a fixed shape and volume, which means they don’t spread out like water or float away like air. Think of an ice cube. Even when it’s cold and hard, it stays in the shape of the cube until it melts.
Imagine a rock in your hand. You can touch it and feel that it’s firm and doesn’t squish like a pillow. This is because the tiny pieces inside, called particles, are packed tightly together. They don’t move around much, which is why the rock stays the same shape.
Picture a tree. The trunk is solid because it stands tall and strong. You can lean against it without worrying it will fall over. The tree’s solid trunk helps it stay upright and reach for the sky. Solids are like that tree trunk; they are sturdy and reliable, giving them the ability to support other things.