Question

Describe what happens during a chemical reaction.

Short answer

A chemical reaction involves breaking and forming bonds to transform reactants into products, conserving mass and being represented by a balanced equation.

Step-by-step solution

Identifying Reactants and Products

In any chemical reaction, we start by identifying the reactants and products. Reactants are the substances you start with, and products are the new substances formed. For instance, in the reaction of hydrogen and oxygen to form water, hydrogen and oxygen are reactants, and water is the product.

Understanding the Process of Reaction

During the chemical reaction, the bonds between atoms in the reactants are broken, and new bonds are formed to create the products. This involves a reorganization of atoms, which is facilitated by the breaking and forming of chemical bonds. This process is typically driven by an energy change, such as the release of energy in an exothermic reaction or absorption of energy in an endothermic reaction.

Conservation of Mass

In a chemical reaction, mass is conserved. This means that the total mass of the products is equal to the total mass of the reactants. This is because atoms are neither created nor destroyed in a chemical reaction; they are merely rearranged. This aligns with the law of conservation of mass, ensuring that the number of each type of atom is the same on both sides of the equation.

Writing a Balanced Chemical Equation

To represent the chemical reaction, we write a balanced chemical equation. This equation shows the exact number of atoms and molecules involved in the reactants and products. An example is the formation of water, which is represented by the equation \(2H_2 + O_2 \rightarrow 2H_2O\). Each element's atoms are balanced on both sides of the equation.

Key concepts

Reactants and Products

In any chemical reaction, understanding the role of reactants and products is key to comprehending the process. Reactants are the starting materials, the substances that undergo transformation during the reaction. These substances react with each other under certain conditions. They are like the ingredients in a recipe, whose interaction produces something new.
On the other hand, products are the substances formed as a result of the reaction. They are the new compounds or elements that emerge once the reaction is complete. For example, when hydrogen gas and oxygen gas react, water is formed as the product. Essentially, the reactants break down and recombine to create these products, showcasing the transformative nature of chemical reactions.

Bond Formation and Breaking

Chemical reactions involve the breaking of old bonds and the formation of new ones. This cycle of bond breaking and forming drives the transformation of reactants into products. When reactants come into contact, the bonds that hold their atoms together may break. This breaking of bonds requires energy, while the formation of new bonds releases energy.
The energy exchange is pivotal in determining the reaction type:

• **Exothermic reactions** – If the energy released in forming new bonds is greater than the energy needed to break the original bonds, the reaction releases energy. An example is combustion, where heat is released.
• **Endothermic reactions** – If more energy is consumed in breaking bonds than is released in forming them, the reaction absorbs energy. Photosynthesis is an illustration of this process.

Understanding bond dynamics is essential for predicting reaction behavior and energy changes.

Conservation of Mass

The principle of conservation of mass is foundational in chemistry. It asserts that mass remains constant during a reaction. Despite the transformation of reactants into products, the total mass does not change.
This constancy is because atoms themselves are neither created nor destroyed during a reaction. They merely rearrange themselves, maintaining the total count of each type of atom. For instance, when you burn a log of wood, it may seem that it disappears, but in reality, the atoms have simply transformed into different compounds like carbon dioxide and water vapor.
Demonstrating this principle ensures accuracy in chemical analysis and validates the predictability of reactions.

Balanced Chemical Equations

Writing balanced chemical equations is a critical skill in showcasing chemical reactions. These equations visually represent how reactants form products and ensure the conservation of mass is clearly displayed.
To balance a chemical equation, one must ensure that the number of each type of atom is equal on both sides of the equation. This balancing act aligns with the conservation of mass, reflecting the reality that atoms are not lost or gained, just rearranged.
An example is the formation of water from hydrogen and oxygen:
\[ 2H_2 + O_2 \rightarrow 2H_2O \]
Here, the count of hydrogen and oxygen atoms is equal on both sides of the equation, making it balanced. A balanced equation provides a clear quantitative depiction of the reaction.