CHEMICAL REACTIONS
What are chemical reactions?
A chemical reaction is a process by which substances are converted to one or more substances.
Types of chemical reactions
Endothermic Reaction - An endothermic reaction is any chemical reaction that absorbs heat from its environment. The absorbed energy provides the activation energy for the reaction to occur. This type of reaction usually feels cold.
Exothermic Reaction - An exothermic reaction is a chemical reaction that releases energy through light or heat. It is the opposite of an endothermic reaction.
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What is the rate of reaction?
The rate of reaction is the speed at which a chemical reaction proceeds, which is, how fast or slow the is the reaction process. The rate of reaction can be observed by watching the disappearance of a reactant or the appearance of a product over time.
What is activation energy?
The minimum energy with which reactants must collide for a reaction to occur. Any chemical reaction results in the breaking of some bonds (needing energy) and the making of new ones (releasing energy). Activation energy is involved in breaking some of the original bonds.
How do we know when a chemical reaction is happening?
A chemical reaction is usually accompanied by easily observed physical effects, such as the release of heat, the evolution of gas, or a colour change.
What is the collision theory?
A basic principle of collision theory is that, in order to react, molecules must collide. These reactant collisions must be of proper orientation and sufficient energy in order to result in product formation.
What affects the rate of a chemical reaction?
Many factors affect the rate of a chemical reaction. These factors include:
Concentration
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The term concentration refers to the amount of a particular substance present in a particular volume of liquid or gas.
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Increasing the concentration of the reactants will increase the rate of reaction
​Temperature
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Increasing the temperature will normally increase the rate of a chemical reaction
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Increase in temperature increases the speed of the particles in liquid and gases which will make the particles collide more frequently
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Increasing the temperature gives the particle more energy and they will hit harder if the molecules collide
Agitation
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The term agitation is also known as stirring the reactants
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Able to increase the rate of reaction
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Ensures that the reactants are kept in contact, it does this by removing the build-up of products around the reactants
​Surface Area
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Increasing the surface area increases the rate of chemical reaction
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If a solid lump was broken into small pieces, then the particles inside the lump are exposed and can react with the solution
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Cutting up or crushing solid reactants into smaller pieces creates a much larger surface in contact between the reactants
​Catalyst
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Chemicals that speed up chemical reactions but are not used up during the reaction
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They reduce the activation energy
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They make it easier for reactants molecules to collide and form products