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 describing 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 not 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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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 the substance itself.

• ​​Properties like color, size, and shape can be observed using your senses.

• ​Melting point and boiling point can be measured with scientific tools.

Chemical Properties

• ​These describe how a substance can change into a completely new substance.

• ​​Flammability, the ability of a substance to catch on fire, is one example.

• ​Oxidation is how a substance reacts with oxygen, such as a nail rusting.

Multiple Choice

Which statement best defines a physical property?

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

• 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.

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Physical vs. Chemical Changes

Physical Change

• The appearance of a substance changes, but its chemical identity remains the same.

• No new substance is formed, and the change can often be reversed easily.

• For example, ice melting into water is a physical change; both are H₂O.

Chemical Change

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

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

• For example, burning wood is a chemical change because it creates ash and smoke.

Multiple Choice

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

• Whether or not a new substance is formed.

• How long the change takes to happen.

• How much energy is used during the change.

• Whether the change involves a solid or a liquid.

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What Are the Signs of a Chemical Reaction?

• A new substance is formed, which is the essence of a chemical reaction.

• You might see gas bubbles (fizzing) or the emission of light.

• Another clue is a distinct and noticeable change in the substance's color.

• A solid (precipitate) forms, or the temperature changes, getting hotter or colder.

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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 becomes smaller.

• The original substance dissolves completely.

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Common Misconceptions

Misconception	Correction
Any change in a substance's appearance is a chemical change.	Changes in appearance, such as melting ice, are often physical changes.
Dissolving a solid in a liquid is always a physical change.	Dissolving an antacid tablet is a chemical change because it produces a gas.
A chemical reaction must produce bubbles or a flame.	Other signs include a change in color, forming a solid, or temperature change.

Multiple Choice

When an iron nail rusts, it combines with oxygen to form a new substance. How does this demonstrate the nail's chemical properties?

• It shows the chemical property of reactivity with oxygen.

• It shows the physical property of changing color.

• It shows that the nail can be easily bent without breaking.

• It shows that the nail has a high melting point.

Multiple Choice

Baking a cake involves mixing ingredients like flour, sugar, and eggs, and then heating them to create a cake. Why is this considered a chemical change?

• Because new substances with different properties (the cake) are formed.

• Because the ingredients have been physically mixed together.

• Because the oven temperature caused a physical change.

• Because the cake has a different shape than the ingredients.

Multiple Choice

A student mixes two clear liquids. They observe the container getting warmer and a yellow solid forming at the bottom. What evidence suggests a chemical reaction occurred?

• The temperature change and the formation of a solid precipitate.

• Only the fact that two liquids were mixed together.

• Only the formation of a yellow color.

• The fact that the container did not produce gas or light.

Multiple Choice

Analyze the process of digesting food. Which statement best justifies the conclusion that digestion involves chemical changes?

• Acids and enzymes in the stomach break food down into new, simpler substances that the body can absorb.

• Food is physically broken down into smaller pieces by chewing in the mouth.

• The food changes in texture and form as it moves through the digestive system.

• Water is absorbed from the food, changing its consistency.

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Summary

• Matter is described by its physical and chemical properties.

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

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

• Evidence of a chemical change includes a color change, temperature change, gas production, or solid formation.

Poll

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

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