Physical and Chemical Properties

Physical and Chemical Properties

Middle School

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Learning Objectives

• Define physical and chemical properties and provide examples of each.

• Differentiate between physical and chemical changes in matter.

• Identify the five key signs that indicate a chemical reaction has occurred.

• Apply knowledge to classify properties and changes as either physical or chemical.

Key Vocabulary

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Matter

The stuff that every physical thing is made of and can be classified by its properties.

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Property

A characteristic or feature of a substance or an object that can be observed or measured.

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Reactivity

The chemical property that describes how readily a substance undergoes a chemical reaction with other substances.

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Physical Change

A change that alters the form of a substance but does not change its basic chemical identity.

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Chemical Change

A change where a substance is transformed into a new substance with different chemical properties.

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Reactant

A substance that is present at the start of and participates in a chemical reaction.

Key Vocabulary

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Precipitate

A solid substance that forms from a solution and settles out during a chemical reaction.

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Flammability

The ability of a substance to burn or ignite, causing fire or combustion, a key chemical property.

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Physical vs. Chemical Properties

Physical Properties

• These are traits you can observe or measure without changing what the substance is.

• You can see properties like color, size, and shape with your own senses.

• Others like melting point and boiling point can be measured with scientific tools.

Chemical Properties

• These describe how a substance changes into a new substance during a chemical reaction.

• Examples include flammability, which is the ability of a substance to catch fire.

• Another example is oxidation, which is how a substance reacts with oxygen, like rusting.

Multiple Choice

Which statement defines a physical property?

• A trait that can be observed or measured without changing what the substance is.

• A trait that describes how a substance changes into a new one.

• A trait that involves a substance reacting with fire or oxygen.

• A trait that can only be measured with scientific tools.

Multiple Choice

What is the key difference between physical and chemical properties?

• Physical properties are measured with tools, while chemical properties are observed with senses.

• Observing a physical property does not change the substance, while observing a chemical property does.

• Physical properties include color and shape, while chemical properties include flammability and rusting.

• Physical properties describe a substance's appearance, while chemical properties describe its reactions.

Multiple Choice

When an iron nail rusts, it demonstrates a specific property. Which of the following best explains what type of property is being shown and why?

• A physical property, because the nail only changed its color and texture.

• A chemical property, because the ability to react with oxygen (rust) changes iron into a new substance.

• A physical property, because the shape and size of the nail remained the same.

• A chemical property, because the nail demonstrated its ability to catch fire.

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Physical vs. Chemical Changes

Physical Change

• ​The appearance or form of a substance changes, but its chemical composition remains the same.

• ​​No new substance is created, and the original substance can often be recovered.

• ​For example, when ice melts into water, it is still chemically H₂O.

Chemical Change

• ​A chemical change results in the formation of one or more entirely new substances.

• ​​The new substances have different chemical properties from the original substance.

• ​For example, burning wood turns it into new substances like ash and gases.

Multiple Choice

What is the main difference between a physical change and a chemical change?

• How long the change takes to happen.

• Whether the change involves a solid or a liquid.

• Whether or not a new substance is formed.

• How much energy is used during the change.

Multiple Choice

When a chemical change occurs, what is true about the result?

• The original substance can be easily recovered.

• The new substances have different chemical properties than the original substance.

• The change only alters the appearance of the substance.

• The change happens very quickly.

Multiple Choice

If you dissolve salt in water, what kind of change has happened and why?

• A physical change, because the salt could be recovered by evaporating the water.

• A chemical change, because the salt dissolved and disappeared.

• A physical change, because the water changed color.

• A chemical change, because a new liquid was formed.

Signs of a Chemical Reaction

• A new substance is formed during a chemical reaction.

• Observable signs include fizzing, light, or a color change.

• A solid forming or a temperature change are also clues.

Multiple Choice

What is the primary result of a chemical reaction?

• A new substance is formed.

• The original substance changes its shape.

• The original substance dissolves completely.

• The original substance becomes smaller.

Multiple Choice

What is the significance of seeing fizzing or a change in color during a process?

• They are the new substances that are formed.

• They are the causes of all chemical reactions.

• They are observable clues that a reaction may be happening.

• They are proof that the reaction has ended.

Multiple Choice

A student mixes two clear liquids in a beaker. The beaker feels warmer, and a white powder settles at the bottom. Which statement is the best conclusion?

• A chemical reaction likely occurred, because a solid formed and the temperature changed.

• Only a physical change occurred, because the two substances mixed together.

• No reaction happened, because there was no fizzing or light produced.

• The new substance that formed was heat.

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Common Misconceptions

Misconception	Correction
Any change in appearance is a chemical change.	Changes in appearance, like melting ice, can also be physical changes.
Dissolving a solid in a liquid is always a physical change.	Dissolving can be a chemical change, like an antacid tablet producing gas.
A chemical reaction must produce bubbles or a flame.	Reactions are also shown by changes in color or temperature.

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Summary

• Matter has both physical and chemical properties that describe it.

• A physical change alters a substance’s form but not its identity.

• A chemical change creates a new substance with different properties.

• Evidence of a chemical change includes a color or temperature change.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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