Grade 9 Chemistry: Energy Changes, Reversible Reactions, and Equilibrium

Vocabulary practice flashcards covering energetic changes, bond calculations, reversible reactions, dynamic equilibrium, and industrial ammonia processes for Grade 9 Chemistry.

Surroundings

Everything around the reacting chemicals, including the solvent, container, and air.

Enthalpy change ($\Delta H$)

The transfer of thermal energy during a reaction, expressed in units of $\text{kJ/mol}$.

Activation energy ($E_a$)

The minimum energy that colliding particles must have to react.

Bond energy

The energy needed to break one mole of a particular bond.

Exothermic reaction

A reaction where thermal energy is transferred to the surroundings, causing the temperature of the surroundings to increase and resulting in a negative enthalpy change ($\Delta H$).

Endothermic reaction

A reaction where thermal energy is taken in from the surroundings, causing the temperature of the surroundings to decrease and resulting in a positive enthalpy change ($\Delta H$).

Reversible reaction

A reaction that can go in both directions (forwards and backwards), represented by the symbol $\rightleftharpoons$.

Hydrated

Containing water of crystallisation.

Anhydrous

Without water.

Closed system

A system where no substances can enter or leave.

Dynamic equilibrium

A state in a reversible reaction where the rates of the forward and reverse reactions are equal and the concentrations of reactants and products do not change.

Position of equilibrium

The relative amounts of reactants and products present at equilibrium.

Catalyst

A substance that speeds up a reaction without being used up and speeds up forward and reverse reactions equally, leaving the position of equilibrium unchanged.

Haber process

An industrial manufacturing process that combines nitrogen from the air and hydrogen from methane to produce ammonia: $\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g)$.

Grey ammonia

Ammonia manufactured from methane without capturing the released carbon dioxide.

Blue ammonia

Ammonia produced from methane where most of the released carbon dioxide is captured and stored underground.

Green ammonia

Ammonia produced using hydrogen made by the electrolysis of water powered by renewable electricity, releasing almost no carbon dioxide.

Eutrophication

An environmental process where fertiliser washed into water bodies causes rapid algal growth, leading to a fall in dissolved oxygen levels.

Explain (Command Term)

Give a detailed account including reasons or causes (using "because" and "therefore").

Evaluate (Command Term)

Weigh up strengths and limitations to make a judgement.