In order to follow the scientific method, your child needs to do the following:
1. Come up with a research question: Which ages faster: bread stored in the fridge, or in the pantry?
2. Make a hypothesis, or an educated guess, about what will happen.
3. List all of the necessary materials to complete the experiment.
4. Detail the procedure: how the experiment will be carried out.
5. Observe, collect data, and record the results.
6. Come to a conclusion based on the results.
Below, I'm including an article in the Resources section which details the steps of the Scientific Method. You may find some helpful details within the article.