Understanding how reactants change into products can be done in several simple ways:

1. Chemical Equations: A balanced equation shows how reactants turn into products. For example, when hydrogen and oxygen come together to make water, we write it like this: $2H_2 + O_2 \rightarrow 2H_2O$

2. Mole Ratios: The numbers in the balanced equation tell us how many parts of each substance are needed. In the above example, $2$ parts of hydrogen ($H_2$) mix with $1$ part of oxygen ($O_2$) to create $2$ parts of water ($H_2O$).

3. Visual Models: Pictures or 3D models can help show the reactants and products. You might use colored balls or shapes to represent different atoms or molecules.

4. Energy Diagrams: Graphs can help show how energy changes during a reaction. They can highlight when a reaction takes in energy (endothermic) or gives off energy (exothermic).

These tools make it easier to understand what happens to reactants and products before and after chemical reactions.