Chemical Reactions

Front

What is a physical change?

Back

A physical change is a change that affects one or more physical properties of a substance without altering its chemical composition. Example: Getting a haircut.

Front

What is a chemical change?

Back

A chemical change occurs when a substance transforms into a different substance with different properties. Example: Rust forming on metal.

Front

What is the formula to produce hydrogen gas?

Back

To produce hydrogen gas, you need a metal such as magnesium and an acid such as hydrochloric acid.

Front

What happens to a candle placed under a jar?

Back

The candle goes out as it uses up the oxygen and releases carbon dioxide.

Front

How many molecules are represented in the chemical formula H2O?

Back

There are 2 molecules of hydrogen and 1 molecule of oxygen in H2O.

Front

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

Back

A physical change does not change the substance's chemical identity, while a chemical change results in the formation of new substances.

Front

What is an example of a physical change?

Back

Examples of physical changes include melting ice, boiling water, and breaking glass.

Front

What is an example of a chemical change?

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Examples of chemical changes include burning wood, rusting iron, and baking a cake.

Front

What is the law of conservation of mass?

Back

The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction.

Front

What are reactants in a chemical reaction?

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Reactants are the starting substances that undergo a chemical change in a reaction.