Chemical reactions don’t just occur in the science laboratory; they happen all around us and often in ways you might not expect. They’re responsible for a wide range of natural phenomena and are essential for sustaining life. 

In fact, around one billion biochemical reactions take place in the human body every second! Even everyday tasks such as boiling an egg, brewing coffee, or washing up involve a chemical reaction of some kind. 

Introduction: everyday chemistry

Even if we exclude the billions of biochemical reactions that naturally occur in living cells, the sheer volume of chemical reactions that take place every day is astounding. Examples of chemical reactions in daily life include natural processes such as photosynthesis, digestion, rusting, and combustion. Other activities like baking, washing with soap and water, or brushing your teeth also rely on chemical reactions.

Some reactions occur faster than a blink of an eye, while others may take years to be noticeable. For example, igniting a match takes a matter of seconds, whereas the weathering of rock occurs over millions of years. 

Many chemical reactions, such as the combustion of petrol in a car engine, are triggered deliberately for a specific reason. Others, however, happen spontaneously or unintentionally without any specific purpose. 

The chemistry of coffee

For many people, drinking coffee is their go-to solution when they want to feel more energised – but have you ever stopped to think about the chemistry behind this much-loved beverage?

There are more than 1,000 chemicals in coffee, but caffeine is by far the most well-known. In fact, it’s the main reason why most adults drink coffee in the first place. Caffeine is a plant alkaloid with the chemical formula C8H10N4O2. As the diagram below shows, it acts as a stimulant because it prevents adenosine binding to the receptors of the central nervous system. In doing so, it delays fatigue and can help you feel more awake.

Infographic showing the chemistry of coffee

About 45 minutes after you consume coffee, the caffeine reaches your liver. It’s then converted into three primary metabolites – paraxanthine, theobromine, and theophylline. Each of these metabolites has specific effects on the body:

  • Paraxanthine increases the breakdown of triacylglycerols or TAGs via hydrolysis, which increases the level of glycerol in the body
  • Theobromine dilates the blood vessels, thereby improving circulation and helping you feel more alert 
  • Theophylline relaxes your muscles and helps you breathe more efficiently

The release of these metabolites is the reason why coffee promotes a feeling of alertness and well-being. To learn more about the chemistry of coffee, read our blog post here.

The transformation of eggs during cooking

Eggs are composed of globular proteins that float in the water around them. These globular structures are held together by weak hydrogen bonds that can be broken by heat or acid.

When an egg is exposed to heat, the proteins start to bounce around and uncurl from their original position. This causes new chemical bonds to form and create a network of interconnected proteins. When this happens, the cooked egg sticks together and becomes edible. Whether you boil or fry an egg, the same chain of chemical reactions occurs. The scientific name for this process is the denaturation of proteins.

Man breaking egg into frying pan

The science of hair dye

When you colour your hair, a series of chemical reactions take place between the hair molecules and the pigment and chemicals in the dye. During the colouring process, the hair undergoes temporary protein denaturation. 

Most types of permanent hair dye contain hydrogen peroxide, which breaks down the natural colour of your hair. It then oxidises a polymeric reaction with the monomers of the dye, allowing the large colour molecules to stay inside the hair.

Applying hydrogen peroxide softens the proteins in the hair so it can absorb the dye more effectively. This chemical reaction is facilitated by the ammonia in the hair dye, which acts as a catalyst. The alkaline pH of ammonia separates the cuticle and allows the colour molecules to penetrate the cortex of the hair.

Fireworks: a blend of chemistry

Gunpowder (also known as black powder) was developed by Chinese alchemists around the 7th century. It’s still used today and is the main ingredient in fireworks, although other chemicals are also added to create the different coloured explosions.

Gunpowder is a mixture of an oxidising agent like potassium nitrate, and a reducing agent such as sulphur or charcoal. When fireworks are ignited, the rapid oxidation of the gunpowder results in an explosive reaction. This burns the other chemicals, which then give off colours based on the way the photons from the atoms are excited when the chemical bonds are broken. 

Chemicals used in tear gas

Tear gas is a chemically-manufactured non-lethal weapon that can be used by the police. It irritates the eyes and respiratory irritation, but generally doesn’t cause lasting or permanent damage. 

The common active ingredient in tear gas is 2-chloroacetophenone. When the pin is removed from a tear gas canister, a mechanism triggers a chain of chemical reactions. It begins with the reaction of charcoal and potassium nitrate. The charcoal is ignited and oxidised by the potassium nitrate. Oxygen is released, which sustains a fire. At high temperatures, grains of silicon melt into hot pieces.

The reaction can potentially become explosive if the pH becomes too acidic. To counteract this, magnesium carbonate in the canister serves as a neutralising agent. This prevents the canister from exploding like a bomb and ensures the tear gas is only released in controlled amounts.


Trillions of chemical reactions happen every day, many without us even realising. Simple activities like drinking coffee, dyeing your hair, or cooking an egg, all involve some type of chemical reaction. Some chemical reactions are triggered deliberately, whereas others happen naturally and spontaneously.


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