Simple Experiments

The use of our senses and instruments to test hypotheses about the physical world.

We've all heard of experiments — done by scientists, in a lab, with complicated, costly equipment. But what are they exactly? Why are they so important to science?

Experiments are a structured and controlled way to answer questions. Sometimes the question is about a fact we think we already know, and we want to see if it's still true — we experiment to confirm a fact. Sometimes we have a guess or prediction that something is true, and we want to test to see if our prediction is true — we experiment to test a hypothesis. And sometimes we set out to look or test for one result and find something unexpected and new — we experiment and make a discovery.

Anyone, anywhere can do experiments. Scientists do them in a special way.

The word “science” comes from scientia, the Latin word for knowledge. There are some characteristics of science as we do it today that make it unique.

• For one thing, scientists focus on gaining knowledge of the physical world. Scientists observe and study the physical world because they can learn about it using their five senses. They often use instruments, like telescopes and microscopes, that can make their senses more powerful. For example, a telescope lets astronomers see objects in deep space like galaxies while microscopes let biologists see tiny living things like cells. These are things we had no idea even existed before the telescope and microscope were invented.
• Scientists also focus on phenonmena that can be measured. Standard units of measurement, such as for size, weight, time, temperature, energy used, and so on, help scientists compare the results of their experiments with each other — even if they come from different countries and speak different languages!
• Another characteristic of science is that it tries to ask questions that can be tested. A scientist can ask a question like, “At what temperature does water boil?” because she would be able to perform an experiment to test the answer.
• Science involves doing experiments that can be repeated by others, so scientists must share their results. A result from an experiment isn't considered knowledge if only one scientist can produce it. Good science can only happen when an answer to a question is backed up by the data from many scientists repeating the same experiment.

As more and more people began to study the natural world through similar ways of observing, measuring, and testing, scholars came up with a term to describe what they were all doing — the Scientific Method. Let's learn more about it.

Scientists start by observing the world around them and asking some question about it. This is a special kind of question, one that we can formulate a hypothesis about and design an experiment to test. Sometimes the experiments are complicated and sometimes the experiments are simple, but the data we collect all work to establish a fact or set of facts that help us understand our world.

The scientific method is simply an organized way of investigating a question — making observations, coming up with hypotheses, testing them through experiments, and measuring results. Benjamin Franklin used this method when he experimented with electricity. At its simplest, it is a five step process.

1. Purpose — State the problem. Ask your question. What do you want to learn? Just about everything starts with a question, usually by looking at the world around you.
2. Observation and Research — Find out as much as you can about the phenomenon you are investigating.
3. Hypothesis — Predict the answer to your question. A hypothesis is not a random guess, but an informed one based on observations.
4. Experiment — Design a test or procedure to prove or disprove your hypothesis. Scientists run experiments more than once to verify that results are consistent. Each time that you perform your experiment is called a run or a trial.
5. Analysis/Conclusion — Record what happened during the experiment. This is called collecting your data. Conclusion- Review the data and explain the meaning of your results. Did your experiment support your hypothesis? You have to be able to prove every answer you give.

Here are some examples of the Scientific Method in action.

If you can ask a question, measure, hear, feel, hear, see, smell, or taste you can be a scientist. Asking questions is first part of finding knowledge. Then dig in to find the answer.

As we've noted before, science is unique because the results of its experiments can be repeated. But usually there are many different factors that cause something to be the way it is or to behave in a certain way. Scientists need a way to tell whether one factor rather than another is a cause. Say, for example, they want to find out the cause of a certain cancer — is it a defective gene? a virus? something in the environment? something else?

To find out, they design an experiment so that changes to one item cause something else to vary in a predictable way. These changing quantities are called variables, and an experiment usually has three kinds: independent, dependent, and controlled. For more detail, Science Buddies has definitions and examples of the different variables.

How can a future scientist repeat an experiment? Easy — because the previous scientists kept careful records of everything they did.

Don't forget to write everything down in your laboratory notebook. You must keep a record of everything you do. There are many ways to organize a notebook, and many choices about what to include. But however you do it, good scientists keep track of their observations, procedures, and questions.

Here is a description of what might go into a science notebook.

Science builds builds on what has been learned and recorded before. This process allows our knowledge about the world to advance. Because of what Benjamin Franklin learned and wrote down about lightning and electricity, we have been able to use that information for more advanced experiments.

You are now ready to move on to doing your own simple experiments!

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