Physical Changes

Physical Changes

Middle School

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Learning Objectives

• Define a physical change and describe its effects on the properties of matter.

• Identify evidence of physical changes, like changes in shape, size, or state.

• Explain why physical changes are often reversible and do not create new substances.

• Differentiate between physical and chemical changes by using examples from everyday life.

Key Vocabulary

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Physical Change

A change that alters the form of a substance, not its chemical makeup or identity.

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State of Matter

The different physical forms matter can take, such as a solid, a liquid, or a gas.

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Phase Change

A transition of matter from one state to another, for example, from a solid to liquid.

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Reversible Change

A change that can be undone, letting matter go back to its original state and properties.

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What Is a Physical Change?

• A physical change does not result in a new substance.

• The chemical identity of the substance stays exactly the same.

• It affects properties like shape, size, form, or state.

• A key feature is that these changes are often reversible.

Multiple Choice

What is the primary characteristic of a physical change?

• A new substance with different properties is formed.

• The change is permanent and can never be undone.

• The identity of the substance does not change.

• Energy is always absorbed in the form of heat.

Evidence of Physical Changes

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Change in Shape or Form

• ​The object's structure is altered, but its material stays the same.

• ​​An example is crumpling a piece of paper into a ball.

• ​You can also break a pencil or squish a soft marshmallow.

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Change in Size

• ​A substance is made smaller without changing its chemical composition.

• ​​Examples include cutting paper into smaller pieces or slicing a pizza.

• ​Chopping a log into smaller pieces is a similar size change.

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Change in State

• ​This is when a substance transitions between solid, liquid, and gas.

• ​​An example is an ice cube melting into liquid water.

• ​Water boiling to become steam is another common phase change example.

Multiple Choice

Which of these is the best example of a physical change involving a change in state?

• Tearing a piece of paper.

• Water freezing and turning into ice.

• Breaking a crayon into two pieces.

• A car's frame getting crunched in an accident.

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Common Misconceptions

Misconception	Correction
Dissolving is a chemical change because the solid 'disappears'.	This is a physical change; the particles have just spread out.
Changes that are hard to reverse must be chemical changes.	The real test is whether a new substance has been formed.
A change in state is a chemical change.	It's a physical change. Water, ice, and steam are all H2O.

Multiple Choice

A student notices that a puddle of water on the sidewalk has disappeared after a few hours on a sunny day. How can this be explained as a physical change?

• The water reacted with the sun to form a new, invisible gas.

• The water changed its state from a liquid to a gas (evaporation) but is still water.

• The heat from the sun caused a chemical reaction that destroyed the water molecules.

• The water soaked into the concrete, which is a chemical change.

Multiple Choice

If you use a blender to make a fruit smoothie, you are causing a physical change to the fruit. Why is this considered a physical change?

• Because the fruit changes color.

• Because the blender adds energy to the fruit.

• Because the fruit is changed in size and form, but not into a new substance.

• Because a new, sweet-smelling substance is produced.

Multiple Choice

A student is given a piece of paper and a glass of water. Which combination of actions would result in only physical changes occurring?

• Burning the paper and then pouring water on it.

• Dissolving salt in the water.

• Tearing the paper into pieces and then getting the pieces wet.

• Mixing baking soda into the water to see if it fizzes.

Multiple Choice

A car crashes and its metal frame is bent and crumpled. Based only on this observation, why is this considered a physical change?

• Because a loud noise was produced during the crash.

• Because the car's appearance is significantly different.

• Because no new substance was created; the bent metal is still metal.

• Because the change is permanent and cannot be easily reversed.

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Summary

• A physical change alters a substance's properties but not its basic identity.

• No new substances are formed during a physical change.

• Phase changes between solid, liquid, and gas are always physical changes.

• Many physical changes are reversible and can be undone.

Poll

On a scale of 1-4, how confident are you about identifying physical changes?

• 1

• 2

• 3

• 4