Chemistry happens in the world around you, not just in the laboratory. Substances interact through chemical reactions or chemical changes to form new products. Every time you cook or clean, it's chemistry. Chemical reactions enable your body to survive and grow. When you take medicine, light a match and breathe deeply, you will react. These examples of everyday chemical reactions are only a small part of the thousands of reactions you experience every day.
Photosynthesis
Plants convert carbon dioxide and water into food (glucose) and oxygen through a chemical reaction called photosynthesis. This is one of the most common and important daily chemical reactions because it is the way plants produce food for themselves and animals and convert carbon dioxide into oxygen. The reaction equation is:
6 CO2 + 6 H2O + light → C6H12O6 + 6 O2
Aerobic cell respiration
Aerobic cell respiration is the opposite process of photosynthesis. Energy molecules combine with the oxygen we breathe to release the energy required by cells, plus carbon dioxide and water. The energy used by cells is chemical energy in the form of adenosine triphosphate or adenosine triphosphate.
The following is the overall equation for aerobic cell respiration:
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (36 ATPs)
Anaerobic respiration
Anaerobic respiration is a group of chemical reactions that enable cells to obtain energy from complex molecules without oxygen. When you run out of oxygen delivered to muscle cells, such as during high-intensity or long-term exercise, muscle cells will breathe without oxygen. The anaerobic respiration of yeast and bacteria is used to ferment to produce ethanol, carbon dioxide, and other chemicals, which can make cheese, wine, beer, yogurt, bread, and many other common products.
The general chemical equation of anaerobic respiration is:
C6H12O6 → 2C2H5OH + 2CO2 + energy
Burning
Whenever you strike a match, light a candle, make a fire, or light a grill, you will see the reaction of burning. Combustion combines energetic molecules with oxygen to produce carbon dioxide and water.
For example, the combustion reaction equation of propane found in gas grids and some fireplaces is:
C3H8 + 5O2 → 4H2O + 3CO2 + energy
Rust
Over time, iron forms a red flake coating called rust. This is an example of an oxidation reaction. Other common examples include the discoloration of copper green and silver.
The following is the chemical equation for iron rust:
Fe + O2 + H2O → Fe2O3. XH2O
Exchange
If you mix vinegar and baking soda to make a chemical volcano or mix milk and baking powder to make a recipe, you will experience a double replacement or double decomposition reaction (plus some other reactions). These components recombine to produce carbon dioxide gas and water. Carbon dioxide forms bubbles in volcanoes, helping baked food rise.
These reactions may seem simple in practice, but they often involve multiple steps. The following is the overall chemical equation for the reaction of baking soda and vinegar:
HC2H3O2(aq) + NaHCO3(aq) → NaC2H3O2(aq) + H2O() + CO2(g)
Electrochemistry
Batteries use electrochemical or redox reactions to convert chemical energy into electrical energy. The spontaneous redox reaction takes place in the primary cell, while the nonspontaneous chemical reaction takes place in the electrolytic cell.
Digestion
Thousands of chemical reactions occur during digestion. When you put food in your mouth, an enzyme in your saliva called amylase begins to break down sugar and other carbohydrates into simple forms that your body can absorb. Hydrochloric acid in the stomach reacts with food to further decompose food, while enzymes decompose protein and fat so that they can be absorbed into the blood through the intestinal wall.
Acid-base reaction
When you mix an acid (such as vinegar, lemon juice, sulfuric acid, or hydrochloric acid) with an alkali (such as baking soda, soap, ammonia, or acetone), you are carrying out an acid-base reaction. These reactions neutralize acids and bases to produce salt and water.
Sodium chloride is not the only salt that can form. For example, this is a chemical equation of acid-base reaction to produce potassium chloride, a common salt substitute:
HCl + KOH → KCl + H2O
Soap reacts with detergent
Soap and detergent are cleaned by chemical reaction. Soap emulsifies dirt, which means that oil stains will adhere to soap, so they can be washed away by water. As a surfactant, detergent reduces the surface tension of water, interacts with oil, isolates them, and washes them off.
Cooking
Cooking uses heat to cause chemical changes in food. For example, when you boil an egg hard, the hydrogen sulfide produced by heating the egg white will react with the iron in the egg yolk to form a gray-green ring around the egg yolk. When you brown meat or baked goods, the Maillard reaction between amino acids and sugar produces a brown and satisfactory taste.
