Changes in the starting materials (reactants) can make it hard to understand what the final products of a chemical reaction will be.

1. Variability: Different reactants can create surprising products. This makes it tough to predict what will happen.

2. Complexity: The paths that reactions take can be different. For example, if you change the temperature or how much of something you use, the results can change too.

Solutions:

• Run controlled experiments to get clear results.
• Use software programs to simulate reactions. These can help you see how reactants and products are related.

Even with these tools, figuring out all the different possibilities can still be challenging.