A solid is one of the states of matter.
Examples of solids include wood, glass, clay, ice, and metals such as steel.
The particles in a solid are closely packed together.
Since solids do not need a container to maintain their shape — they have a definite shape — does that mean that their shape cannot change?
Not at all!
The shape of solids can change when an outside force is applied — such as when they are bent, pressed, hammered, or cut.
This lesson focuses on physical changes that solid materials undergo.
Solid materials can be changed by:
These are really just terms that we use to describe what is being done to a solid material, and a lot of these processes are similar to each other or have similar results, such as breaking and cutting, or bending and twisting.
Solid materials can also undergo many of these processes in such quick succession as to be one continuous process — the act of kneading dough, for example, can involve pressing, stretching, and folding, one after the other.
Not all solids can undergo these processes, and some undergo a certain process more easily than others. For example, you can’t fold a rock you find in your garden, but you can fold cloth. A plastic straw can be bent easily, but not a metal straw. Paper can be cut readily, but if you try to stretch it, it might get torn instead.
When solid materials are bent, their size and shape — their physical appearance — may change but no new material is formed.
Example: bending your body!
When solid materials are pressed, their size and shape may change. Their texture may also change — something rough may be smoothened by pressing. Still no new material is formed — only a physical change happens.
Example: pressing clay
When solid materials are hammered, their size, shape, and possibly even their texture may be changed. Again, only physical changes take place; no new material is formed.
Materials that can be hammered and formed into shapes without breaking are said to be malleable. Metals, in particular, are known to be malleable.
Example: hammering gold into jewelry
When solid materials are cut, their size and shape may change but, again, no new material is formed.
There is a huge range of tools for cutting. The most common are scissors, which we can use at home to cut paper, for example. Saws can be used to cut wood. Metal cutters can vary from snips and pliers to huge machines for cutting iron and steel. Some machines even use flames, lasers, high-pressure water, and plasma to cut solid materials.
Example: cutting grass
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