Physical and Chemical Changes

What’s the difference between a physical and a chemical change?

Kids Talking Science

Sara's avatar

Hey Mark! Did you notice anything different today?

Mark's avatar

Yeah—you were actually on time for class!

Sara's avatar

Ha-ha. What about my hair?

Mark's avatar

Oh, right—you changed your hair color!

Sara: Good! You noticed the change in me.

Mark: Changes happen in nature all the time. It's fun to observe them.

Sara: Am I part of nature too?

Mark: Of course!

Sara: Then nature must be beautiful, right?

Mark: Nature is the most beautiful thing there is.

Sara: Great, now I’ll actually listen to you. Go on, science star!

Mark: Matter is always moving and changing. And we divide changes into two types: physical and chemical changes.

Sara: Just like properties of matter can be physical and chemical?

Mark: Exactly. If a new substance is created, it’s a chemical change. If not, it’s a physical change.

Sara: What kind of change is it when we freeze water?

Mark: Does it turn into a new substance, Sara?

Sara: No. It becomes ice, but ice is still water—just in a different state.

Mark: Right! Freezing, like other changes of state, is a physical change—because no new substance is formed.

Sara: Got it! And when we burn a piece of charcoal while making a barbecue, the black stuff turns into something else, right? So that's a chemical change?

Mark: Yes! Burning charcoal produces carbon dioxide gas—a completely new substance with different properties and particles.

Key Science Concepts

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Sara and Marko are having fun trying to come up with as many examples of physical and chemical changes as they can. Now it's our turn to write down the clear scientific definitions of these two important types of change.

Physical Changes
Changes in which no new substances are formed. The material may change shape or state, but it stays the same substance.
Chemical Changes
Changes that result in the formation of new substances. The original substance is transformed into something different.

Science Fun Fact

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A burning candle shows us both types of changes at once!

Burning a Candle – Both a Physical and a Chemical Change!

Candle burning

When you light a candle, both types of changes happen at the same time!

  • Physical change: The wax melts. It just changes from solid to liquid—its substance stays the same.
  • Chemical change: The flame burns the wax and turns it into gases like carbon dioxide and water vapor—these are new substances!

Quick Science Quiz

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