Matter and Its Interactions

Physical Changes happen when something changes how it looks, feels, or is shaped, but it is still the same kind of matter.

In other words, the material does not turn into something new. It may be bigger or smaller, straight or bent, solid or liquid, but it is still the same thing.

For example, if you tear paper, it is still paper. If ice melts, it is still water. These are physical changes.

Let’s learn how to spot a physical change.

Main Idea: A physical change changes the appearance, size, shape, or state of matter.

• Appearance means how something looks.
• Size means how big or small it is.
• Shape means the form of an object.
• State means if something is a solid, liquid, or gas.

When a physical change happens, the matter is still the same material after the change.

Physical changes can happen in many ways.

• Cutting
• Tearing
• Folding
• Bending
• Breaking
• Melting
• Freezing

These actions change what something looks like, but they do not make a brand-new material.

Changing shape is a physical change.

If you bend a straw, it is still a straw. If you fold a piece of paper, it is still paper. The object changed shape, but not what it is made of.

Changing size is a physical change.

If you cut a sandwich in half, you now have two smaller pieces. But it is still the same sandwich. If you break a crayon, the pieces are still crayon.

Changing state is a physical change too.

Matter can be a solid, liquid, or gas.

• Solid: keeps its shape, like an ice cube
• Liquid: flows, like water
• Gas: spreads out in the air, like steam

When ice melts, it changes from a solid to a liquid. But it is still water.

When water freezes, it changes from a liquid to a solid. But it is still water.

This means melting and freezing are physical changes.

How can we tell if something is a physical change?

1. Ask: Does it only look different now?
2. Ask: Is it still the same kind of material?
3. If the answer is yes, it is probably a physical change.

Here are some clues:

• The object may be smaller or bigger.
• The object may have a different shape.
• The material may change from solid to liquid or back again.
• It is still the same material in the end.

Worked Example 1: Tearing paper

You have one whole sheet of paper. You tear it into two pieces.

What changed? The size and shape changed.

What stayed the same? It is still paper.

Answer: This is a physical change.

Worked Example 2: Melting an ice cube

An ice cube sits in the sun. After a while, it turns into a puddle of water.

What changed? The state changed from solid to liquid.

What stayed the same? It is still water.

Answer: This is a physical change.

Worked Example 3: Breaking a pencil

A pencil falls and snaps into two parts.

What changed? The size and shape changed.

What stayed the same? The pieces are still parts of the same pencil.

Answer: This is a physical change.

Worked Example 4: Freezing water

You pour water into an ice tray and put it in the freezer. Later, the water turns into ice cubes.

What changed? The state changed from liquid to solid.

What stayed the same? It is still water.

Answer: This is a physical change.

Let’s compare some physical changes.

• A folded towel is still a towel.
• A crushed can is still the same can material.
• A broken cookie is still cookie pieces.
• Melted butter is still butter.

In each example, the matter changed in a way we can see, but it did not become a new kind of matter.

Things to remember:

• Physical changes are changes you can often see.
• The material keeps being the same kind of matter.
• Shape, size, and state can change.
• No new material is made.

Quick Check

Is each one a physical change?

• Cutting an apple into slices — Yes, it is still apple.
• Rolling clay into a ball — Yes, it is still clay.
• Ice cream melting — Yes, it is still ice cream.
• Snapping a twig — Yes, it is still the same twig.

Summary

A physical change changes how matter looks, feels, or changes state, but it does not change what the matter is. If something is still the same material after the change, it is a physical change. Tearing, bending, breaking, melting, and freezing are all common physical changes.