Many students complain that they do not understand chemistry and consider it one of the most difficult school subjects. For example, one phrase “heterogeneous reactions” causes panic in many students. In some ways, they are no doubt right. But nevertheless, chemistry can and should be friends. She surrounds our lives everywhere. The best advice for students who are determined to make friends with this difficult science is to learn the material given by the teacher for each lesson. Preparing for classes is not based on the principle: “I won’t be asked today, so you can’t not teach me!” Only with such an approach to business chemistry will become an open book for you. And you will begin to understand and notice it in all manifestations of our lives.
In this article we will focus only on such a chemical concept as heterogeneous reactions. How to understand this term? If the reaction is more or less clear with the word (it means the interaction of substances), then with the word “heterogeneous”, many students have problems. Here we need to recall the translation from the Greek word “heteros” - which means different, different.
Heterogeneous reactions: examples from life
Heterogeneous reactions occur between substances that are different in nature, or rather the physical state. Even from elementary school, each student knows that any substance can be in 3 aggregate states (or in 3 phases): in solid form, in the form of a liquid, or in a gaseous state. So, a reaction is considered heterogeneous if the substances entering it are in different aggregate states, for example:
- gas + liquid
- gas + solid
- liquid + solid.
If the substances reacting with each other are in the same state of aggregation, then such reactions are called homogeneous. The word can also be translated from Greek: "homos" - the same, similar.
Homogeneous and heterogeneous reactions are widely found in our lives. Consider, for example, the reaction of burning wood. Firewood is, by and large, a chemical substance of organic origin - cellulose. Without a doubt, firewood is a substance that is in a solid state of aggregation. They burn due to the action of oxygen. Oxygen is a gas. As a result of the wood burning reaction, coal, carbon dioxide and water are formed. Firewood burning, like alcohol burning, is a heterogeneous reaction. Examples can be given ad infinitum.
1) Rusting iron. Firstly, this is a chemical reaction, because as a result a new substance is formed from iron - rust iron (III) hydroxide. Secondly, this is a heterogeneous process, since iron is a solid substance, and water and air oxygen, under the influence of which rusting occurs, are liquid and gas, respectively. This process can be written using the following reaction equation :
Fe (solid) + H2O (g) + O2 (g) = Fe (OH) 3 (solid)
2) Extinguishing soda with vinegar. Many mothers use this chemical reaction to make gingerbread dough. In this case, solid NaHCO3 soda in powder form and a 3% solution of acetic acid CH3COOH are taken, therefore, this is also a heterogeneous process, since 2 substances in different aggregate states interact. This process is described by the equation:
NaHCO3 + CH3COOH = CH3COONa + H2O + CO2
Note that the reaction products here are in different states of aggregation - sodium acetate CH3COONa and water + H2O are liquids, and CO2 is carbon dioxide.
3) The blackening of bronze monuments or silverware under environmental conditions is also a heterogeneous reaction.
I hope that now this term does not cause you any difficulties. And if you still have questions, do not be too lazy to open a chemistry textbook for grade 8 and repeat the material you have covered again. This will never hurt, because it is not for nothing that the Russian proverb says: “Repetition is the mother of learning!”