Chemical reactions occur everywhere in the world around you, not just in a chemistry lab. Here are 20 examples of chemical reactions in everyday life and a closer look at what’s happening on a molecular level.
How to Recognize a Chemical Reaction
The first step to recognizing chemical reactions in the world around you is to identify when a reaction is taking place. Chemical reactions cause chemical changes. In other words, substances interact and form new products. Not every change in matter is a chemical reaction. For example, melting ice, tearing a sheet of paper into strips, and dissolving sugar in water are physical changes that don’t change the chemical identity of matter.
Here are some signs of a chemical reaction. If more than one sign is present, it’s like a reaction has occurred:
- Temperature change
- Color change
- Bubbling or gas production
- Formation of a solid called a precipitate when liquids are mixed
20 Examples of Chemical Reactions in Everyday Life
Here are some broad examples of chemical reactions in daily life:
- Aerobic cellular respiration
- Anaerobic respiration (including fermentation)
- Oxidation (including rust)
- Metathesis reactions (such as baking soda and vinegar)
- Electrochemistry (including chemical batteries)
- Soap and detergent reactions
- Acid-base reactions
- Rotting of food
- Electroplating metals
- Disinfecting surfaces and contact lenses
- Hair color
- Leaves changing color with seasons
- Salt keeping ice off roads and helping to freeze ice cream
A Closer Look at Chemical Reactions in Daily Life
Here is a closer look at some everyday reactions, along with some chemical equations.
You experience combustion reactions when you strike a match, burn a candle, start a campfire, or light a grill. In a combustion reaction, a fuel reacts with oxygen from air to produce water and carbon dioxide. Here is the reaction for the combustion of propane, a fuel used in gas grills and some fireplaces:
C3H8 + 5O2 → 4H2O + 3CO2 + energy
Plants use a chemical reaction called photosynthesis to convert carbon dioxide and water into food (glucose) and oxygen. It’s a key reaction because it generates oxygen and yields food for plants and animals. The overall chemical reaction for photosynthesis is:
6 CO2 + 6 H2O + light → C6H12O6 + 6 O2
Aerobic Cellular Respiration
Animals use the oxygen provided by plants to perform essentially the reverse reaction of photosynthesis to get energy for cells. Aerobic respiration reacts glucose and oxygen to form water and chemical energy in the form of adenosine triphosphate (ATP). Here is the overall equation for aerobic cellular respiration:
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (36 ATP)
Anaerobic Cellular Respiration
Organisms also have ways to get energy without oxygen. Humans use anaerobic respiration during intense or prolonged exercise to get enough energy to muscle cells. Yeast and bacteria use anerobic respiration in the form of fermentation to make everyday products, such as wine, vinegar, yogurt, bread, cheese, and beer. The equation for one form of anerobic respiration is:
C6H12O6 → 2C2H5OH + 2CO2 + energy
Rust, verdigris, and tarnish are all examples of common oxidation reactions. When iron rusts, it changes color and texture to form a flake coating called rust. The reaction also releases heat, but it usually occurs too slowly for this to be noticeable. Here is the chemical equation for the rusting of iron:
Fe + O2 + H2O → Fe2O3. XH2O
Electrochemical reactions are redox (oxidation and reduction) reactions that convert chemical energy into electrical energy. The type of reaction depends on the battery. Spontaneous reactions occur in galvanic cells, while nonspontaneous reactions take place in electrolytic cells.
Digestion is a complex process that involves thousands of chemical reactions. When you put food in your mouth, water and the enzyme amylase breaks down sugar and other carbohydrates into simpler molecules. Hydrochloric acid and enzymes break down proteins in your stomach. Sodium bicarbonate released into the small intestine neutralizes the acid and protects the digestive tract from dissolving itself.
Soap and Detergent Reactions
Washing your hands with water isn’t a chemical reaction because you’re just mechanically rinsing away grime. If you add soap or detergent, chemical reactions occur that emulsify grease and lower surface tension so you can remove oily grime. Even more reactions occur in laundry detergent, which may contain enzymes to break apart proteins and whiteners to prevent clothes from looking dingy.
Just mixing dry ingredients usually doesn’t result in a chemical reaction. But, adding a liquid ingredient often results in a reaction. Cooking with heat also causes reactions. Mixing flour, sugar, and salt is not a chemical reaction. Neither is mixing oil and vinegar. Cooking an egg is a chemical reaction because heat polymerizes proteins in egg white, while the hydrogen and sulfur in the yolk can react to form hydrogen sulfide gas. When you heat sugar, a reaction called carmelization occurs. When you heat meat, it browns due to the Maillard reaction. Baked goods rise due to carbon dioxide bubbles formed by the reaction between baking powder or soda and liquid ingredients.
Acid-base reactions occur anytime you mix an acid (e.g., lemon juice, vinegar, muriatic acid, battery acid, carbonic acid from carbonated beverages) with a base (e.g., baking soda, ammonia, lye). A good example of an acid-base reaction is the reaction between baking soda and vinegar to form sodium acetate, water, and carbon dioxide gas:
NaHCO3 + HC2H3O2 → NaC2H3O2 + H2O + CO2
In general, a reaction between an acid and a base produces a salt and water. For example, if you react muriatic acid (HCl) and lye (NaOH), you get table salt (NaCl) and water (H2O):
HCl + NaOH → NaCl + H2O
In this reaction, two clear liquids form another clear liquid, but you can tell a reaction occurs because it releases a lot of heat.