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.

Fill in the Blank

The particle model explains that matter is composed of tiny particles that are in constant motion. These particles can be ___ or molecules.

Multiple Choice

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

• Liquid

• Solid

• Gas

• Plasma

Fill in the Blank

A substance that has a fixed shape and volume is called a ___.

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

Fill in the Blank

In a chemical reaction, one or more new ___ are formed.

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

Fill in the Blank

In a chemical reaction, the total number and type of ___ stay the same.

Fill in the Blank

A chemical reaction is the transformation of one or more substances into ___ 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