Which of the following observations indicates that a chemical reaction has occurred?

• Change in state

• Formation of a precipitate

• No colour change

• Change in size

Why does a precipitate form in a chemical reaction?

• Because the reactants become lighter

• Because the reaction absorbs heat

• Because at least one product is insoluble

• Because the reaction speeds up

What is a neutralisation reaction?

• A neutralisation reaction is a biological reaction between an acid and a base that results in the formation of water and a salt.
• A neutralisation reaction is a chemical reaction between two acids resulting in the formation of water and a salt.
• A neutralisation reaction is a physical reaction between an acid and a base that results in the formation of water and a salt.
• A neutralisation reaction is a chemical reaction between an acid and a base that results in the formation of water and a salt.

Which tests can be used to identify hydrogen?

• squeaky pop test

• limewater test

• relights glowing splint

• smells bad

How can the formation of a precipitate indicate a chemical reaction? (indicate means show)

• It indicates the formation of a gas

• It indicates the loss of reactants

• It indicates the formation of a new substance

• It indicates a decrease in temperature

According to the particle model, what happens to particles during a chemical reaction?

• They disappear

• They change color

• They rearrange to form new substances

• They increase in size

How do we know the picture is showing a chemical reaction? Choose two.

• Particles have rearranged

• The size of particles changed

• A new substance was formed

• A gas was released

Which gas test involves passing the gas through lime water?

• Hydrogen test

• Carbon dioxide test

• Oxygen test

• Nitrogen test

What is the result of passing carbon dioxide through lime water?

• Limewater remains unchanged

• Limewater turns milky

• Limewater turns blue

• Limewater turns yellow

Which gas test involves relighting a glowing splint?

• Hydrogen test

• Carbon dioxide test

• Oxygen test

• Nitrogen test