Question

A ____ speeds up a reaction without being consumed.

Short answer

A catalyst is a substance that speeds up a chemical reaction without being consumed in the process, by lowering the activation energy required for the reaction to occur.

Step-by-step solution

Identifying the term for the substance

The term we are looking for is "catalyst." A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process.

Understanding the role of a catalyst

Catalysts work by lowering the activation energy required for a reaction to occur, which allows the reaction to proceed more quickly or at a lower temperature. They are not consumed in the reaction and can therefore continue to facilitate additional reactions.

Key concepts

Reaction Rate

The reaction rate tells us how quickly a chemical reaction proceeds. It is often expressed as the change in concentration of a reactant or product over time. Understanding how fast or slow a reaction occurs is vital in both industrial and everyday chemical processes.
Factors affecting the reaction rate include:

• Concentration: Increasing the concentration of reactants typically increases the reaction rate because more reactant molecules are available to collide and react.
• Temperature: Higher temperatures generally raise the reaction rate by supplying energy that makes molecules move faster, increasing the likelihood of collisions.
• Catalysts: Adding a catalyst speeds up a reaction by lowering its activation energy, allowing more molecules to acquire the energy needed to react.
• Surface Area: When a reactant is solid, grinding it into a powder can increase its surface area, leading to more collisions and an increased reaction rate.

By understanding and controlling these factors, chemists can optimize the speed of reactions for desired outcomes.

Activation Energy

Activation energy is the minimum energy that reactant molecules must possess for a chemical reaction to occur. It acts as an energy barrier that must be overcome for reactants to transform into products. A higher activation energy means a slower reaction because fewer molecules will have enough energy to reach this threshold.
Envision this concept as a hill that reactants must climb over:

• If the hill (activation energy) is high, few molecules have the energy to climb it, resulting in a slow reaction.
• If the hill is low, many molecules can easily surpass it, speeding up the reaction.

Catalysts play a crucial role here by lowering the activation energy. They provide an alternative pathway for the reaction with a lower energy requirement, making it easier for the reaction to proceed quickly. This reduction in activation energy is why reactions in the presence of a catalyst can occur more rapidly or at lower temperatures.

Chemical Reaction

A chemical reaction involves the transformation of reactants into products through breaking and forming chemical bonds. These reactions are characterized by observable changes such as color change, temperature change, gas production, or precipitate formation.
Consider the basic components of a chemical reaction:

• Reactants: The starting materials that undergo a transformation.
• Products: Substances that result from the reaction, composed of the reactants' atoms rearranged.
• Catalysts: Substances that speed up the reaction without being consumed, making them a valuable tool for controlling reaction rates.

Chemical reactions are classified based on patterns such as synthesis, decomposition, single replacement, double replacement, and combustion. The ability to influence and predict these reactions is foundational in chemistry, enabling the creation of a vast array of products and materials.