Physical Sciences Gr 11 Revision Terms 3 and 4 Chemical change

Enthalpy (H)

The sum of the internal energy (E) of a system and the pressure (P) times volume (V).

Enthalpy change (ΔH)

The transfer of energy to or from a system, typically occurring with a heat transfer.

Exothermic reaction

A process that releases energy, typically in the form of heat, to the surroundings.

Endothermic reaction

A process that absorbs energy from the surroundings, often resulting in a temperature decrease.

Activation energy

The minimum energy required to initiate a chemical reaction.

Open System

A system where matter and energy can leave the system.

Closed System

A system where matter cannot leave, but energy can.

Isolated System

A system where neither matter nor energy can leave.

Heat of reaction

The amount of energy absorbed or released during a chemical reaction.

Potential Energy Graphs

Graphs that depict the change in potential energy during a chemical reaction.

Catalyst

A substance that increases the rate of a chemical reaction without changing its products.

ΔH < 0

Indicates an exothermic reaction where the products have lower potential energy than the reactants.

ΔH > 0

Indicates an endothermic reaction where the products have higher potential energy than the reactants.

Surroundings

Everything outside the system, where observations and measurements are taken.

Reactants

The starting substances in a chemical reaction that undergo transformation to form products.

Products

The substances formed as a result of a chemical reaction.