Chemical Equation and Reactions

A chemical reaction or a chemical equation can be defined as a process in which a chemical change occurs. In a chemical reaction, the substances take part in the reaction, react, and are transformed into new substances. 

• The substances or elements in the chemical reaction must be present in the gaseous, liquid, or solid form
• The properties of these products do not exist in the original substances known as reactants
• The product may be an element, compound, or another pure substance
• How quickly a chemical reaction takes place depends on a number of factors, including the energy (heat) added to the reaction and how much is available
• The rate at which the atoms of the reactants break apart and join together – this is also called the reaction rate – affects how quickly they react with one another
• The type of chemical bonds present can also make a difference in how fast a reaction will take place
• An extremely cold environment may also make it take longer for molecules to either react with one another or move around within their container
• In a chemical reaction example, we can say that the two things present in the reaction can be termed as:
  • Substances or things that are participating in a reaction are known as reactants
  • After the reaction, a new substance is formed, and thus, it is called a product
• Examples of chemical change are:
  • When magnesium is burnt in the air, this forms magnesium oxide, and thus it is a chemical reaction

2Mg(s) + O2(g) 2MgO(s)

A piece of magnesium ribbon that is burned in the air yields a substantial amount of white smoke. This is mainly due to the liberation of MgO and CO gases and secondarily due to the combustion of some parts of the carbon coating left by the sanding process. 

Properties of Chemical Reactions

• Gas Evolution

Zinc and dilute sulphuric acid react to produce hydrogen gas, water, and zinc sulfate. Adding zinc to dilute sulphuric acid takes time at first, but once the reaction has started it produces hydrogen rapidly. The solution changes colour from clear to cloudy as it is oxidized and the hydrogen gas accumulates in the test tube.

Zn  + dilute H2SO4  → ZnSO4 + H2(g)

• State Change

When the wax is heated, it melts into a liquid before evaporating and turning back into a solid. It becomes neither a liquid nor a gas. But after you add an oxidising agent to the molten wax, it becomes oxidized (and hence, partly reduced). When the oxidizing agent reacts with the oxidizable element in meltable wax, carbon dioxide is formed and water is produced. The whole process of complete combustion of melted wax takes place at the temperature of boiling water in the open air.

• Temperature Change

In this experiment, you will identify both exothermic and endothermic reactions. Given an unknown mixture of two solutions, you are required to identify which of the solutions will absorb heat (endothermic reaction)and which will release heat(exothermic reaction). There is a rise in temperature in both these processes, by virtue of the chemical reaction that takes place. Combustion and Respiration are examples of exothermic reactions whereas melting of ice and baking of bread are examples of endothermic reactions.

• Colour Change

A colour change may also indicate that a chemical reaction has occurred. A reaction has occurred if two solutions are mixed and there is a colour change that is not simply the result of dilution of one of the reactant solutions. It may occur when a solid and liquid are mixed. For example, the colour of the solution turns blue to green, when we add an iron nail or iron pieces to the Copper sulphate solution.

 Fe + CuSO4 (Blue colour)   → FeSO4 (Green colour) + Cu (brown deposit)

• Chemical Change Examples 

The chemical change examples include rusting of iron, made from the reactants iron and oxygen gas. Here the reactants are being oxidised, (receiving oxygen) and rust (Fe2O3) is formed as the product which does not change the chemical properties significantly. You also observe a similar reaction with magnesium, where it forms MgO (oxide) as it changes its state completely into a new compound. The colour of the formed compound remains the same in both reactions, orange in the case of rusting of iron and white in case of oxidation of magnesium. These chemical change examples will help you understand the topic better.

Properties of Chemical Change 

• The first and most important thing to realise here is that molecules always react differently depending on the type of reaction they undergo
• Molecules also change their form when in contact with different solvents and under different conditions such as temperature, pH, and pressure
• When a chemical reaction occurs, the molecules of the reactants rearrange to form new compounds
• The process of change in the arrangement of subatomic particles—the atoms or groups of atoms that make up the molecules—is called a chemical change
• During a chemical change in an endothermic reaction, energy is absorbed whereas during exothermic reaction energy is released
• A chemical change occurs when atoms are rearranged in a compound, a new substance is formed, or old compounds are broken down into elements
• A chemical change always results in energy being released
• Chemical reactions play an important role in everyday life They are involved in the burning of fossil fuels and in the processes that produce plastics and synthetic rubber

Conclusion 

In this material, we got to learn about chemical reactions and chemical equations that can be important in the exams. The properties of the chemical reactions mentioned in this will help the students to understand the topic better. Moreover, we got to understand the chemical changes and the properties associated with them as it will help the students to have good knowledge about the questions. The chemical equations and reactions given in this material will help the students to learn more.