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Chemical Reaction

 


In our earlier blogs, we talked about the fundamentals of Chemistry and Physics based on syllabus of grade 9. In this blog we are going to discuss fundamentals of chemistry based on the syllabus of grade 10. We will start our first blog with the discussion of chemical reactions.

 

Chemical Reaction

A chemical reaction is a process in which atoms or molecules of one or more substances are rearranged to form new substances. Chemical reactions are all around us, from the metabolism of food in our bodies to the combustion of fuels.

There are four obvious observations that help us to figure out whether the chemical reaction has taken place or not. Those are;

  • Change in state.
  • Change in color.
  • Evolution of gas.
  • Change in temperature.

For example, let’s suppose a magnesium ribbon is burned and the ashes collected in a watch glass. To determine if the reaction has taken place in this process or not, we will check for the given observations. We can check that the state of magnesium is still solid, but the state of oxygen is turned from gaseous state to solid state. Magnesium ribbon has a shiny, silvery gray color. After burning in the presence of oxygen it turned into white powder of magnesium oxide. While burning the magnesium ribbon we can also see the evolution of gas and change in temperature of the magnesium oxide. After this observation we can definitely say about the example that the reaction has taken place in this example.

To represent the chemical reaction in short and simple language, we write the reaction in a symbolic format. This symbolic format is known as a chemical equation.


Chemical equation

The chemical equation shows the change of reactants to products through an arrow placed between them. The reactants are written on the left-hand side with a plus sign (+) in between them and the products are written on the right-hand side with a plus sign (+) in between them. The arrowhead points towards the product and shows the direction of the reaction.

For example, let’s write the word-equation of the previous example first.

Magnesium + Oxygen → Magnesium Oxide

By putting the atomic symbols instead of name, we can turn word-equation into chemical equation. Like this

Mg + O2 → MgO

In this equation, Mg stands for Magnesium, O stands for oxygen and MgO stands for magnesium Oxide.

Every chemical reaction can be divided into two parts.

  • Reactants:  the substances that start the reaction are called reactants. They are written on the left-hand side of the chemical equation. For example, Magnesium (Mg) and Oxygen (O) are reactants in the previous equation.
  • Products: The substances that are produced by the reaction are called products. Products are written on the right-hand side of the chemical equation. For example, Magnesium Oxide (MgO) is the product in the previous equation.

 

Every chemical equation can be divided into two categories.

  • Skeleton chemical equation: A skeleton chemical equation is a chemical equation in which the number of elements is not necessarily equal on either side of the equation. It is a simplified version of a chemical equation that shows only the reactants and products of the reaction. The physical states of the reactants and products are not shown in a skeleton chemical equation.
    For example, Mg + O2 → MgO is a skeleton chemical equation. Because the number of elements is not equal on both sides of the equation.
  • Balanced chemical equation: A balanced chemical equation is a chemical equation in which the number of atoms of each element is equal on both sides of the equation. That means, mass is conserved during the chemical reaction.
    For example, 2Mg + O2 → 2MgO is a balanced chemical equation. Because the number of elements is equal on both sides of the equation.





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