What is a Chemical Reaction?

A chemical reaction is a transformation of matter in which reactants (initial chemical species) are converted into products (final chemical species). According to Lavoisier’s law of Conservation of Mass, the mass of the reactants is equal to the mass of the products. A chemical reaction causes the breaking and formation of new chemical bonds.

We can tell that a reaction is taking place by observing a change in the solution’s color, the development of an odor, a change in the state of matter (solid, liquid, or gas), or the formation of a solid precipitate.

The Combustion Reaction

The first and most important chemical reaction is combustion. Combustion involves the oxidation of a fuel by an oxidizing agent (usually oxygen in the air), accompanied by the release of heat and electromagnetic radiation, which often includes light. It is important because it is a redox reaction, in which one compound is oxidized (an atom that loses electrons) and the other is reduced (an atom that gains electrons).

Signs that a Chemical Reaction is taking place

• Change in the color of the liquid solution;
• Formation of a solid precipitate;
• Gas development;
• Release or absorption of energy in the form of heat;

States of Matter: Properties

(g) Gas state: They have a very low density compared to solids and liquids; they fill the space of the container holding them; they consist mainly of empty space; gas molecules are widely spaced apart from one another; collisions between molecules and with the walls of the container are also possible; they represent the most disordered state of all.

(l) Liquid state: They have a higher density than gases but a lower density than solids; they occupy a fixed volume and take on the shape of the container holding them; the molecules are closer together, and collisions between them occur more frequently than in gases; they can evaporate at a certain temperature; a liquid can offer resistance to flow (viscosity).

(s) Solid state: They represent the most ordered state of matter; there is no possibility of movement within a solid, or if there is, it is minimal; they usually have higher densities than liquids and gases; they can be more or less hard (hardness) when subjected to physical forces.

Balancing a Chemical Reaction

It reads: Two moles of H₂O are produced after consuming 2 moles of H₂ and 1 mole of O₂.

Overall, the reaction is balanced because there are the same number of H and O atoms on both the left and right sides.

Bibliographic sources:

1. Ralph H. Petrucci, F. Geoffrey Herring, Jeffry D. Madura, Carey Bissonnette (2017). General Chemistry: Principles and Modern Applications (11th ed.) by Pearson Education Canada Inc.

Read more on Chemical Fundamentals 101:

• 05. Chemical Formulas explained: The Laws of Conservation of Mass and Definite Proportions: Chemical formulas represent the elements in molecular or ionic compounds, such as CO₂ for carbon dioxide and NaCl for sodium chloride. They can be empirical, molecular, or structural, each providing different information about the compound. Empirical formulas show simplest ratios, while molecular formulas indicate actual ratios and structural formulas illustrate atomic connections.
• 04. The Properties of Groups in the Periodic Table: The text discusses elements in Groups 1, 2, 3-12, 17, and 18 of the Periodic Table. Alkali and alkaline earth metals are reactive, with distinct conductivity properties. Transition metals are malleable and ductile. Halogens are nonmetals, lacking conductivity, while noble gases are very unreactive, colorless, and odorless.