GCSE Chemistry - Factors Affecting the Rate of Reaction

The video introduces four main factors that affect the rate of chemical reactions: temperature, concentration or pressure, surface area, and the presence or absence of a catalyst.

Before diving into the factors, the video explains collision theory, stating that particles must collide with sufficient energy (activation energy) to react. If the energy is insufficient, they just bounce off each other. The rate of reaction depends on the energy of particles and the frequency of collisions.

Increasing temperature gives particles more energy, causing them to move faster. This leads to more frequent collisions and collisions with higher energy, increasing the likelihood of exceeding the activation energy and thus speeding up the reaction rate.

Concentration (for solutions) and pressure (for gases) both refer to the number of particles per unit volume. Increasing either means more particles are present, leading to more frequent collisions and a higher reaction rate.

A higher surface area increases the reaction rate. For example, powdered magnesium reacts faster than a solid block. This is because a larger surface area allows for more contact points for collisions with other reactants, increasing collision frequency.

Catalysts are substances that speed up reactions without being consumed. They work by lowering the activation energy through an alternative reaction pathway, leading to a higher proportion of successful collisions. Transition metals and enzymes (biological catalysts) are common examples.