Chemical Changes GIZMOS

A white powder is added to a solution. The images show observations made before the powder is added, just after the powder has been added, and a little while later. (The liquid in the small beaker is phenol red solution.) What evidence shows that a chemical change has taken place?

• A gas is produced

• The pH changes

• The temperature changes

• All answers are correct

A reaction produces a gas, which is collected in a glass cylinder. When a glowing splint is placed inside the container, it burns brightly, as shown. Which gas was produced in the reaction?

• Hydrogen

• Oxygen

• Carbon Dioxide

• Ammonia

A chemical reaction is done in the setup shown, resulting in a change of mass. What will happen if the same reaction is done in a sealed container that is placed on the electronic balance?

• • The mass will decrease because matter is lost in this reaction.

• The mass will stay the same because the gases produced in the reaction are kept inside the container.

• The mass will increase because the solids react with gas to produce more solids.

• There is not enough information to predict what will be produced.

Based on its formula, what type of reaction occurs between silver nitrate (AgNO₃) and copper (Cu)?

2AgNO₃ + Cu → 2Ag + Cu(NO₃)₂

• Synthesis

• Decomposition

• Single replacement

• Double replacement

When hydrogen peroxide (H₂O₂) is added to potassium iodide (KI) solution, the hydrogen peroxide decomposes into water (H₂O) and oxygen (O₂). The chemical equation for this decomposition reaction is:

2H₂O₂ → 2H₂O + O₂

In this reaction, the potassium iodide is needed for the reaction to happen, but it isn’t changed in the reaction and can be used again. What is the role of potassium iodide in this reaction?

• Reactant

• Product

• Precipitate

• Catalyst

_______ occurs when one or more substances are transformed into different substances.

• A splint test

• A chemical change

• A catalyst

• A mixture

The terms endothermic and exothermic are used to describe which type of change?

• color

• gas

• temperature

• pH

An indicator, such as phenol red, will give you what type of information about a chemical reaction?

• a change in mass

• a product change

• a temperature change

• a pH change