An exothermic reaction is a chemical reaction that generates heat. Exothermic is a Greek word that means exterior and thermic means heat. The exothermic reaction is a chemical reaction where the heat is released. The reaction is studied in explosion and fire studies as well as in forensic science experiments.
Exothermic reactions take place in our day-to-day lives. Only the speed of this reaction changes. The reaction is seen when an iron piece starts to rust. This is an exothermic reaction in a mild form. Another example is when you boil water.
The normal room temperature cannot make the water to boil. This is an endothermic reaction, and when the same water lets out heat and starts to freeze, an exothermic reaction begins, and the water becomes ice cubes.
In an exothermic reaction, the temperature of the objects that surround it starts to increase. This happens because the exothermic process leaves out heat. The endothermic process, on the other hand, takes up the heat from the surrounding.
Let us now read through some simple but common exothermic reaction examples found in real life.
Making ice cubes
The melting of ice is an endothermic reaction. Now take water in an ice tray and place it in your refrigerator. The water starts to let out its heat and cools down, and converts to ice cubes. It is an exothermic reaction.
So what happens to the heat that was in the water? It gets transferred to the environment in the form of air. The heat moves out through the compressor. The compressor is made of coils that help the heat to pass through wires, and for this reason the compressor is placed towards the back of the fridge.
Forming snow in clouds
Snow formation is an exothermic reaction. The clouds are formed because of water vapour condensation. Some clouds also have ice particles, and this gets heated from crystallisation and condensation.
The exothermic process always lets the heat out, which is the energy that it gives out in the chemical process of forming snow in clouds. Heat gets generated, and this is a by-product of the reaction.
Burning of candle
The candle body is made of paraffin, and this is a hydrocarbon. When paraffin burns along with the flame. it reacts with oxygen and creates water and carbon dioxide, this is an exothermic reaction because it lets out heat in the atmosphere and the other products.
The chemical reaction will determine the amount of heat that is generated between the oxygen and the hydrocarbon. Oxygen is present on the flame’s outer edge, and the atmosphere is also made of oxygen.
Rusting of iron
Rusting iron is a chemical reaction. Iron is oxidised at a slow pace. Rusting is thus an exothermic reaction between oxygen and iron. Rusting happens when the iron is either in its pure form or in the form of an alloy.
The process causes the release of heat, and this occurs when iron and oxygen come in contact with each other. Rust is a chemical substance that forms when iron comes in contact with moisture.
Burning of sugar
The sugar that you eat goes through a complex chemical reaction in the body. Sugar is formed of oxygen, carbon, and hydrogen, and when it goes inside the body, it produces heat, and this results in energy. This heat then goes out from the human body and gets added to the environmental heat. Thus the burning of sugar, as you see, is an exothermic reaction.
Forming an ion pair
Ions in the gaseous form react intensely with water and makes hydrated ions. This is an exothermic process. The smaller is the radius of the ion; the bigger is its charge. Because of this, the ion hydration enthalpy grows bigger, and this causes a huge exothermic reaction.
Cellular respiration is an exothermic reaction that happens in each cell of the body and provides energy to the cells to carry out vital body functions. The sugar molecules present in the body break down into water and carbon dioxide molecules, and thus they release energy. The energy that is released because of sugar breakdown is used to synthesize ATP which is the molecule of the cell that carries energy.
The lighting of a matchstick
Matchsticks are made of sulfur, phosphorus, and many other chemicals. When you ignite the matchstick, it causes a chemical reaction between the sulfur, phosphorus, and air. This causes a fire that releases heat. The burning of a matchstick is thus an exothermic process.
Setting the concrete and cement
Cement hydration is a process that occurs between water and cement. Cement hydration is an exothermic process. When water and cement are mixed, it causes the heat to get rapidly liberated in a few minutes. This heat evolution is caused because of a chemical substance that is present in cement.
The reaction of water and a strong acid
Heat is needed to break any chemical bond. However, when a chemical bond is formed, it causes the release of energy. The bond formation is an exothermic reaction. Let us take the example of HCl, which is a strong acid. When this strong acid is dissolved in water, it causes the hydrogen and the water to react in a complex reaction.
The hydrogen reacts, and this releases a huge amount of heat concentrated within a small area. This draws the polar water molecules to it. The hydrogen ion causes a covalent bond along with water. It also attracts a huge number of hydrogen bonds that are very strong. So this is an exothermic reaction that takes place when a strong acid and water are mixed with each other.
Exothermic reactions in our real-life could be gentle and safe or dramatic. Explosive reactions are caused by physical and chemical reactions that cause energy release forming flames, sparks, and smoke, sometimes even sound.
The exothermic reaction releases thermal energy, which flows out from the system. The thermal energy is denoted as a negative because this energy is being released out. The initial potential energy of the reactants was more than the energy that was released from the product.