Experiments
What is an experiment?
An experiment is one type of investigation scientists use to answer questions by gathering evidence. Experiments are often done in a laboratory, where scientists can control the conditions, but you can do an experiment at home! In an experiment, scientists change one thing to observe whether that causes something else to change. The things that are changing in an experiment are called variables.
How do I design an experiment?
In an experiment, everything is kept the same, except one thing is changed to see how that changes the outcome. The things that are changing in an experiment are called variables. A variable is any factor, trait, or condition that can exist in differing amounts or types. An experiment usually has three kinds of variables: independent, dependent, and controlled. These are highlighted in the example below.
Let's say that you grandmother is interested in growing plants. She wonders "How the amount of water I give to my plants affect how tall the plants grow?" She could design an experiment by putting two of the same plants, in the same kind of soil, in a place where they receive the same amount of sunlight. She would change the amount of water she gave each plant, while keeping everything else the same. Then, after some time, she could compare how tall each plant grew. This would help her understand how the amount of water affected her plants!
What she changed (independent variable): The amount of water she gave each plant.
What she kept the same (controlled variables): The type of plant, soil, and amount of sunlight.
What she measured and compared (dependent variable): The height of the plants.
Can you think of something else your grandmother could change about how she cared for her plants that might affect how tall they grow? Now you're thinking like a scientist!
What do I need to keep in mind?
Experiments don't have to be expensive or use fancy equipment, and they don't have to be done in a laboratory! You can be a scientist in your own home!
Scientists try to predict what will happen in their experiments. Sometimes results will not match the prediction, and that's OK!
When you repeat your experiment, you should get a similar result-- you might need to test multiple times to be sure that you can trust your results!
It's important that you only change one thing, otherwise, you won't be able to tell which one made a difference in your results!