Finding Causes and Effects

Today you will learn how to find cause-and-effect relationships and use them to explain why things happen in science.

A cause is the reason something happens. An effect is what happens because of that cause. Scientists look for these pairs all the time. When you know the cause, you can explain the effect. You can even predict what will happen next time.

Think about a hot Texas afternoon in August. You leave a cup of ice water on the picnic table outside. An hour later, the ice is gone and the cup is dripping wet on the outside. The heat from the air is the cause. The melted ice is one effect. The water drops on the outside of the cup are another effect, because water vapor in the warm air cooled down and turned back into liquid on the cold cup. One cause can lead to more than one effect.

To investigate a cause-and-effect relationship, you change one thing and watch what happens. You could put one cup of ice in the shade and one cup in the sun. Everything else stays the same, like the size of the cup and the amount of ice. If the ice in the sun melts faster, you have evidence that sunlight causes faster melting. Evidence is the information you collect that supports your idea.

Be careful, though. Two things happening at the same time does not always mean one caused the other. Ice cream sales go up in summer, and so do mosquito bites. Ice cream does not cause mosquitoes. Hot weather causes both. Good scientists test their ideas instead of guessing.

Cause and effect shows up in every science, from weather to plants to machines. It helps you solve problems, too. If your flashlight will not turn on, you look for the cause, like dead batteries.

Try it: A plant on a windowsill leans toward the glass. What is the cause?