Year 9 Chemistry Revision

Multiple Choice

Which of the following best describes a molecule?

• A single atom

• A pure substance made of one type of atom

• Two or more atoms held together by chemical bonds

• A mixture of different substances

Multiple Select

Which of the following are signs of a chemical reaction?

• Change in color

• Formation of a gas

• Change in shape only

• Production of heat

Open Ended

Describe how atoms are rearranged during a chemical reaction and why this is important for understanding changes in matter.

Multiple Choice

Which state of matter has a fixed volume but takes the shape of the bottom of its container?

• Liquid

• Solid

• Gas

• Plasma

Multiple Select

Which of the following are examples of physical changes?

• Boiling water

• Burning wood

• Folding paper

• Rusting iron

Open Ended

Explain why the same substance is present before and after a physical change, using examples from the images.

Multiple Choice

What happens to the particles of a substance during a physical change?

• They remain the same but move to new positions

• They change into different particles

• They disappear

• They combine to form a new substance

Multiple Choice

Which of the following best describes a physical change as shown with the iron nail?

• The composition of the iron changes

• The shape of the iron changes but it remains iron

• A new substance is formed

• The iron melts

Multiple Choice

Which of the following is NOT a sign of a chemical change?

• Change in colour

• Change in temperature

• Change in shape

• Production of light

Open Ended

Explain how the Law of Conservation of Mass applies to chemical reactions. Use your own words and examples if possible.

Multiple Choice

In a chemical reaction, what do we call the substances that are present before the reaction takes place?

• Products

• Reactants

• Solvents

• Mixtures

Multiple Choice

Which statement best describes the Law of Conservation of Mass?

• Matter can be created or destroyed in a closed system.

• Matter can only be transformed, not created or destroyed, in a closed system.

• The mass of products is always greater than the mass of reactants.

• The total mass of a system can change during a chemical reaction.

Multiple Select

Based on the chemical equation shown, which of the following are conserved during the reaction?

• The total mass of the substances

• The number of atoms of each element

• The volume of the substances

• The color of the substances

Multiple Choice

How many Hydrogen atoms in 3H₂O

• 1

• 2

• 3

• 6

Multiple Choice

How many Carbon atoms in 5CO₂

• 1

• 2

• 5

• 10

Multiple Choice

How many Carbon atoms in 6CuCO₃

• 1

• 3

• 6

• 18

Multiple Choice

When balancing chemical equations, you can change the...

• Coefficient

• Subscript

Multiple Choice

Mg + O2 --> MgO

• Synthesis

• Decomposition

• Displacement

Multiple Choice

CuSO₄ + Zn --> ZnSO₄ + Cu

• Synthesis

• Decomposition

• Displacement

Multiple Choice

H₂O₂ --> H₂O + O₂

• Synthesis

• Decomposition

• Displacement

Multiple Choice

In an exothermic reaction, energy is:

• Absorbed from the surroundings

• Released to the surroundings

• Stored in bonds of products

• Destroyed

Multiple Choice

Which statement best describes an endothermic reaction?

• Energy is released and the temperature of surroundings increases.

• Energy is absorbed and the temperature of surroundings decreases.

Multiple Choice

A student mixes two chemicals and the beaker feels warmer. What does this indicate?

• The reaction is endothermic.

• The reaction is exothermic.

Multiple Choice

Which reaction has a faster rate, red or blue?

• Red

• Blue

Multiple Choice

What is meant by the “activation energy” of a reaction?

• The maximum energy particles can have

• The energy needed to break bonds and start the reaction

• The energy released when bonds form

• The total energy of the products

Multiple Choice

According to collision theory, for a chemical reaction to occur:

• Energy must always be absorbed

• The temperature must be very high

• Particles only need to touch each other

• Particles must collide with enough energy and the correct orientation

Multiple Choice

Increasing the temperature of a reaction mixture usually makes the reaction faster because:

• Particles move slower and collide less often

• Particles have more energy, so more collisions are successful

• Activation energy increases

• The particles are larger

Multiple Choice

A student crushes a solid tablet before dissolving it in water to react. According to collision theory, why does this increase the reaction rate?

• It lowers the activation energy

• It reduces the surface area for collisions

• It increases the surface area for collisions

• It cools the particles

Multiple Choice

Why does a catalyst increase the rate of reaction?

• It increases the number of collisions

• It lowers the activation energy needed

• It is used up during the reaction

Multiple Choice

Which of the following will increase the rate of reaction according to collision theory?

• Decreasing the concentration of reactants

• Decreasing the surface area of a solid reactant

• Increasing the concentration of reactants

• Lowering the temperature