Chemical Properties and Changes

Changes of Matter (feat. Law of Conservation)

By J Senghor

​There are two types of changes in matter; physical change and chemical change. As the names suggest, a physical change affects a substance’s physical properties and a chemical change affects its chemical properties.

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• ​occur when there is a change to one or more physical properties

• ​does not result in a change in chemical identity

• are reversible​ in many cases

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Physical Changes

• occur when one substance changes into another​ after a chemical reaction

• ​"ingredients" are called reactants and end results are called products

• irreversible​

Chemical Changes

Multiple Choice

A physical change...

• changes the physical properties of an object, but does not create a new substance.

• creates a new substance and cannot be undone.

Multiple Choice

A chemical change

• changes the physical properties of an object, but does not create a new substance.

• creates a new substance and cannot be undone.

• Production of gas/bubbles​

• Production of odor

• Change in color

• Formation of precipitate

• Exothermic/Endothermic reaction

• ​Release of light

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Identifying chemical changes

​Signs of a chemical change

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Chemical reactions tend to happen more quickly at higher temperatures. When temperatures are higher, atoms and molecules have more kinetic energy which enable them to move around and rearrange more quickly and easily.

This law states that mass cannot be created or destroyed during a physical or chemical change. The mass you have before the change is always equal to the mass after the change. For example, a chemical reaction between 93g of mercury and 7g of oxygen will produce 100g of mercuric oxide.

The Law of Conservation of Mass

Multiple Choice

What kind of change occurs if matter changes in amount, size, or shape?

• substance change

• chemical change

• physical change

• elemental change

Multiple Choice

Which of the following is NOT an example of a physical change?

• Smashing a soda can

• Wood breaking apart

• Salt dissolving in water

• Iron rusting

Multiple Choice

A change where one or more new substances are created.

• Physical Change 
• Chemical Change 

Multiple Choice

Which of these is a result of a chemical change?

• A mixture
• A solution
• A new substance
• Melting or freezing

Multiple Choice

Which of the following is a sign that a chemical reaction has occurred?

• change in shape
• melting
• formation of a gas
• dissolving

Multiple Choice

Physical or Chemical Change?  Baking a cake.

• Chemical Change
• Physical Change

Multiple Choice

Which of the following is NOT an example of chemical change?

• sour milk
• burning wood
• breaking a pencil
• rust

Multiple Choice

Which block model could represent Na₂SO₄?

Multiple Choice

Which block model could represent SrCl₂?

Multiple Choice

Matter can not be created nor destroyed: it can only be

• Destroyed a little bit
• Invisible
• Transformed, changed
• None of the above

Multiple Choice

If reaction starts with 20g of reactants it should produce 

• a total of 40g of products
• a total of 10g of products
• a total of 80 g of products
• a total of 20g of products

Multiple Choice

According to the Law of Conservation of Mass, what happens to the wood and oxygen when it is burned?

• The wood disappears.

• It stays the same chemically.

• The atoms in the wood and oxygen rearrange and form smoke and ash.

• Nothing.

• Building an Argument about Changes:

  • We can use what we see to show if a substance changes in two ways: physically or chemically.

  • Observing Physical Changes:

    • Changes in state (solid, liquid, gas) without forming new substances.

    • Changes in shape or size that can be reversed.

  • Observing Chemical Changes:

    • Color changes indicating a new substance is formed.

    • Formation of bubbles or gas, showing a chemical reaction.

    • Release of heat or light during the change process.

  • 
    

Multiple Choice

Which of the following is an example of a physical change?

• Color changes indicating a new substance is formed.

• Formation of bubbles or gas, showing a chemical reaction.

• ) Changes in state (solid, liquid, gas) without forming new substances.

• Release of heat or light during the change process.

Multiple Select

What indicates a chemical change taking place?

• Changes in shape or size that can be reversed.

• Changes in state from solid to liquid.

• Color changes indicating a new substance is formed.

• Formation of bubbles or gas that disappear quickly.

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• Backing Up Our Claims:

  • Give examples of changes we can see and explain why they are physical or chemical.

• Examples of Changes:

  • Physical Changes:

    1. Melting Ice: Ice becomes water, still the same substance.

    2. Tearing Paper: Paper rips into smaller pieces, but it's still paper.

  • Chemical Changes:

    1. Burning Wood: Wood becomes ash and smoke, not wood anymore.

    2. Rusting of Iron: Iron reacts with air to form rust, changing its makeup.

Multiple Select

During a science experiment, you mixed baking soda and vinegar in a test tube. As a result, the mixture started fizzing and bubbling. You and your lab partner are discussing if this reaction represents a physical or chemical change. Choose ALL of the evidence that supports a chemical change has occurred.

Which of the following observations support that a chemical change has occurred by mixing baking soda and vinegar?

• The mixture started fizzing and bubbling.

• The test tube felt warm to the touch after mixing the substances.

• A new substance with a different color was formed.

• The mixture can be easily separated back into baking soda and vinegar.

Multiple Choice

In a kitchen experiment, you mixed flour and water to create a dough. Your friend claims that the dough formation is a chemical change. Choose ALL of the evidence that supports a physical change has occurred.

Which of the following observations support that a physical change has occurred by mixing flour and water to create dough?

• The dough can be flattened and reshaped multiple times.

• The dough changes color when baked in the oven

• The dough becomes hard and solid after baking.

• The dough smells different than the original flour and water mixture.