Chemical Reactions for Grade 9

What are the four main types of chemical reactions?

• Synthesis, Decomposition, Single Replacement, Double Replacement

• Combustion

• Neutralization

• Redox Reaction

Define a synthesis reaction and provide an example.

• The displacement of zinc by copper: Zn + CuSO4 → Cu + ZnSO4.

• The combustion of methane: CH4 + 2O2 → CO2 + 2H2O.

• An example of a synthesis reaction is the formation of water: 2H2 + O2 → 2H2O.

• The decomposition of water: 2H2O → 2H2 + O2.

What is a decomposition reaction? Give an example.

• The combination of hydrogen and oxygen to form water is a decomposition reaction.

• The rusting of iron is an example of a decomposition reaction.

• An example of a decomposition reaction is the breakdown of water (H2O) into hydrogen (H2) and oxygen (O2) gas when subjected to electrolysis.

• The digestion of food in the stomach is a decomposition reaction.

Explain what a single replacement reaction is.

• A single replacement reaction is a chemical reaction where one element replaces another in a compound.

• A single replacement reaction is when elements are created from nothing in a chemical reaction.

• A single replacement reaction involves two compounds exchanging elements.

• A single replacement reaction is a process where two elements combine to form a compound.

What is a double replacement reaction? Provide an example.

• CaCO3 + H2SO4 → CaSO4 + CO2 + H2O

• NaOH + HCl → NaCl + H2O

• An example of a double replacement reaction is: AgNO3 + NaCl → AgCl + NaNO3.

• H2 + O2 → H2O

What is the pH scale used for?

• The pH scale is used to measure the acidity or alkalinity of a solution.

• To measure the temperature of a solution.

• To determine the color of a solution.

• To assess the viscosity of a solution.

How do acids and bases react with each other?

• Acids turn into bases upon reaction with each other.

• Acids and bases explode when mixed together.

• Acids and bases neutralize each other to form water and a salt.

• Acids and bases form gas and a liquid when they react.

What is the difference between a strong acid and a weak acid?

• Strong acids do not conduct electricity in solution.

• Weak acids have a higher pH than strong acids.

• Strong acids fully dissociate in solution; weak acids partially dissociate.

• Strong acids are always more concentrated than weak acids.

What is the role of a catalyst in a chemical reaction?

• A catalyst slows down a chemical reaction by increasing the activation energy.

• A catalyst is a substance that is consumed in the reaction.

• A catalyst changes the products of a chemical reaction.

• A catalyst speeds up a chemical reaction by lowering the activation energy.

How does temperature affect the rate of a chemical reaction?

• Temperature has no effect on the rate of a chemical reaction.

• Higher temperatures slow down chemical reactions.

• Temperature increases the rate of a chemical reaction.

• Temperature only affects physical changes, not chemical reactions.