Grade 12 Physical Sciences: Chemical Change and Reaction Rates

Vocabulary flashcards covering chemical reaction rates, activation energy, catalysts, and experimental variables for Grade 12 Physical Sciences.

Activation energy

The minimum energy that reacting particles must possess for a successful collision to occur.

Reaction rate

The change in concentration of reactants or products per unit time.

Factors affecting reaction rate

The six factors include temperature, concentration of reactants, pressure (for gases), surface area (particle size), catalysts, and the nature of reactants.

Independent variable

The factor that is manipulated in an experiment, such as temperature or concentration.

Dependent variable

The factor being measured in an experiment, such as reaction rate or the time taken for a cross to disappear.

Controlled variable

A factor kept constant during an experiment to ensure a fair test, such as the volume of $HCl$ or the concentration of $Na_2S_2O_3$.

Exothermic reaction

A reaction where more energy is released than absorbed, or where the energy of the reactants is greater than the energy of the products.

Catalyst

A substance that speeds up a reaction by providing an alternative pathway of lower activation energy.

Effective collisions

Successful collisions between particles that result in a reaction because the particles possess energy equal to or greater than the activation energy.

Copper(II) oxide ($CuO$)

A substance identified in the transcript as a catalyst used to increase the reaction rate or to measure gas production.

Reaction rate trend

The rate decreases with time because the concentration of reactants decreases, resulting in fewer effective collisions per second.

Reaction rate units

Standard units used in calculations such as $mol \cdot dm^{-3} \cdot s^{-1}$ or $mol \cdot min^{-1}$. Alphabetical substitutions for chemical amounts often use $g \cdot mol^{-1}$ for molar mass.