Reactivity - Explanation

Explain collision theory

For a chemical reaction to occur, particles must collide at the correct orientation with sufficient energy

Explain rate of reaction

change in concentration of reactants or products per unit of time

Explain how changes in temperature affect reaction rates. (speed of particles)

“AT A HIGHER TEMPERATURE, THE PARTICLES HAVE

MORE (AVERAGE) KINETIC ENERGY. THE PARTICLES

ARE MOVING FASTER - THIS MEANS MORE COLLISIONS

PER SECOND, WHICH MEANS MORE SUCCESSFUL

COLLISIONS PER SECOND, WHICH MEANS A FASTER

RATE.

Explain how changes in concentration affect reaction rates.

“A HIGHER CONCENTRATION MEANS MORE

PARTICLES PER VOLUME. THIS MEANS

MORE COLLISIONS PER SECOND, WHICH

MEANS MORE SUCCESSFUL COLLISIONS PER

SECOND, WHICH MEANS A FASTER RATE.”

Explain how changes in surface area affect reaction rates.

“THE MORE SURFACE AREA, THE MORE

AREA/PLACES THERE ARE FOR COLLISIONS TO

HAPPEN. THIS MEANS MORE COLLISIONS PER

SECOND, WHICH MEANS MORE SUCCESSFUL

COLLISIONS PER SECOND, WHICH MEANS A

FASTER RATE.”

Explain how catalysts affect reaction rates.

provides an alternate pathway for a reaction, lowering the activation energy required. This increases the proportion of collisions that are successful, so more successful collisions occur per second and the rate of reaction increases.

Explain how temperature affects reaction rates

HAVING A HIGHER AVERAGE KINETIC ENERGY

MEANS MORE OF THE PARTICLES WILL HAVE ENOUGH

ENERGY TO OVERCOME THE ACTIVATION ENERGY.

THIS MEANS A HIGHER PERCENTAGE OF THE

COLLISIONS WILL BE SUCCESSFUL, SO THIS MEANS

MORE SUCCESSFUL COLLISIONS PER SECOND, WHICH

MEANS A FASTER RATE.”

Describe activation energy

minimum energy required by the reactant particles to initiate a chemical reaction.

How do catalysts decrease activation energy

lowers the activation energy by providing an alternate pathway for the reaction to occur. Therefore, a greater number of reactant particles will collide with sufficient energy to overcome the activation energy, which increases the number of successful collisions per second, increasing the rate of reaction

How can the rate of reaction be measured

monitoring the change in concentration of reactants or products over time. The rate is then calculated as the change in the measured property divided by the time taken.

What is an open chemical system?

An open system allows both matter and energy to be exchanged with the surroundings. in an open beaker, gases can escape and heat can be transferred freely.

What is a closed chemical system?

A closed system allows energy transfer but not matter transfer. So no reactants or products can enter or leave the container.

Define the term reversible reaction

A reaction that can go both forward and backward. the products can react to form the original reactants again.

explain how changes in concentration of reactants and products eventually lead chemical reactions to reach an equilibrium

At the start of a reversible reaction, the concentration of reactants is high, so the forward reaction occurs quickly, producing products. As products form, their concentration increases, so the reverse reaction speeds up.
Eventually, the forward and reverse reactions occur at the same rate.