Introduction to Chemical Reactions

TL;DR

Chemical reactions are processes where atoms rearrange to form new substances. Reactants are the starting materials, and products are what you end up with. We represent these changes using chemical equations to show what's happening.

1. The Mental Model

Think of chemical reactions like building with LEGOs. You start with certain blocks (reactants), break them apart, and then connect them in new ways to build something completely different (products). The individual LEGO bricks (atoms) themselves don't change, just how they're connected.

2. The Core Material

Chemical reactions are fundamental to everything from cooking to how your body works. They're essentially processes where one or more substances, called reactants, are transformed into different substances, called products. This transformation involves breaking existing chemical bonds and forming new ones.

What Happens in a Reaction?

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When a chemical reaction occurs, you're not creating or destroying atoms, just rearranging them. This is a core principle in chemistry: the Law of Conservation of Mass. It means that the total mass of the reactants must equal the total mass of the products. You simply can't lose or gain atoms in the process.

Let's look at a common example: burning methane gas.

Methane (CH₄) + Oxygen (O₂) → Carbon Dioxide (CO₂) + Water (H₂O)

In this reaction:
* Reactants: Methane (CH₄) and Oxygen (O₂)
* Products: Carbon Dioxide (CO₂) and Water (H₂O)

The carbon atoms, hydrogen atoms, and oxygen atoms present at the start are all present at the end, just bonded together differently.

Evidence of a Chemical Reaction

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