Chemical Reactions in Junior Science

What is a chemical reaction?

• A chemical reaction is a process that involves only one chemical substance.

• A chemical reaction is a process that does not involve any change in properties of substances.

• A chemical reaction is a process that leads to the transformation of physical substances.

• A chemical reaction is a process that leads to the transformation of one set of chemical substances to another.

List three signs that a chemical reaction has occurred.

• Release of light

• Formation of a precipitate, evolution of gas, and change in color.

• Formation of a solid

• Change in temperature

Explain the difference between physical and chemical changes.

• Physical changes occur in living organisms, while chemical changes occur in non-living things.

• Physical changes are always faster than chemical changes.

• Physical changes involve a change in color, while chemical changes do not.

• Physical changes are reversible, while chemical changes are irreversible.

What are reactants and products in a chemical reaction?

• Reactants are the substances formed at the end of a chemical reaction

• Products are the substances present at the beginning of a chemical reaction

• Reactants and products are interchangeable terms in a chemical reaction

• Reactants are the substances present at the beginning of a chemical reaction, and products are the substances formed as a result of the reaction.

Define exothermic and endothermic reactions.

• Endothermic reactions release energy

• Exothermic reactions release energy, while endothermic reactions absorb energy.

• Exothermic reactions absorb energy

• Exothermic reactions have no energy change

Give an example of a chemical reaction that releases energy.

• Decomposition of hydrogen peroxide

• Electrolysis of water

• Combustion of methane (CH4)

• Photosynthesis of glucose

What is a catalyst in a chemical reaction?

• A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process.

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

• A catalyst is a substance that decreases the rate of a chemical reaction.

• A catalyst is a substance that has no effect on the rate of a chemical reaction.

Describe the Law of Conservation of Mass in relation to chemical reactions.

• In chemical reactions, the total mass of the reactants equals the total mass of the products.

• In chemical reactions, the total mass of the reactants is always less than the total mass of the products.

• The Law of Conservation of Mass states that mass can be created or destroyed during a chemical reaction.

• Chemical reactions can violate the Law of Conservation of Mass by changing the total mass of the reactants and products.

What is a balanced chemical equation?

• A balanced chemical equation is one where the reactants are in a higher quantity than the products.

• A balanced chemical equation has an equal number of atoms for each element on both the reactant and product sides.

• A balanced chemical equation is one where the products are in a higher quantity than the reactants.

• A balanced chemical equation has an equal number of molecules for each element on both the reactant and product sides.

Explain the role of enzymes in biological chemical reactions.

• Enzymes have no role in biological chemical reactions

• Enzymes have the same function as hormones in biological chemical reactions

• Enzymes play a crucial role in facilitating and regulating biological chemical reactions by lowering activation energy and increasing reaction rates.

• Enzymes inhibit biological chemical reactions