The Scientific Method

#1: State the problem in question form

You notice something interesting about the world that you do not understand and you want to figure out what is happening. You are just asking a question about something that interests you.

Suppose that you go to the store to buy soil for your potted plant. There are lots of types of soil and you do not know which one will work best. You might ask this question, Will my ivy plant grow better in soil A (you would give the actual name of the soil here) or in soil B (give the actual name)?

#2: Gather information about the problem

Probably someone else has had a similar question or has asked a question that will help you get the information that you need. You can gather information by reading books, talking to people, making observations. . . .

You could gather information about your question by reading the information on the bag of soil. If it lists ingredients that you are not familiar with, you could look up information about those ingredients in a book. You could ask someone who knows something about soil or about ivy what they think about your question.

#3: Form a hypothesis

A hypothesis is your educated guess about what is happening. We say that it is a guess because you do not know the answer to your question at this point. We say that it is educated because you did some research, so you have probably made a good guess. Another important thing to know is that a hypothesis is stated in an "If..., then..." statement. You will not always see hypotheses written in that format, but that is the format that we expect to see in class and for the science fair.

Your hypothesis might be: If I put two ivy plants in two different types of soil, then the plant in soil A will grow faster. Notice that the if part of the statement describes what you are going to do, and the then part tells what you think will happen.

#4: Perform the experiment

Now you have to check to see if your guess was correct, so you do an experiment. There are a few important words that you need to know with an experiment. You want to test just one thing in the experiment. That one thing is called the variable. It will be too confusing for you if you try to test more than one variable at a time. Since you are only testing one variable, there are a lot of things that you do not want to change. The things that you keep the same are called the constants.

Now you need to do the experiment. The variable in this case is the type of soil: soil A or soil B. You only want to test one thing, so you want everything else to stay constant. Therefore, you want to use the same kind of ivy plants. They should be the same size and in the same kind of containers. You need to place them close to each other so that they get the same amount of sunlight. You need to water them exactly the same. They should have the same amount of soil, but one plant needs to have soil A while the other has soil B. You will want to watch the plants for at least a few weeks.

#5: Record and analyze the data

During your experiment, you will be observing and measuring. You need to write down your observations and measurements. Remember that scientists use metric units (meters, degrees Celsius) so you want to measure everything using metric units. Then you need to look at your data to see if it answers your question. It is best to use tables and graphs for this step.

Your data in this case might be the height of the plant, the number of leaves, or the longest branch on the plant. Say that you count the number of green leaves every day. You would record that information in a table and at the end, you would make a graph comparing the two plants.

#6: State a conclusion

In your conclusion you need to say if your hypothesis was right or wrong. It is fine for your hypothesis to be wrong. It would not make any sense to do the experiment if you knew that your hypothesis was correct. You should also summarize what you found out. You can talk about new experiments that you would like to do that would answer questions that you thought of when you were doing this experiment. You can also talk about sources of error here. A source of error is a mistake that might have been made in the experiment. It is something that is not really your fault, but it might affect the results. For example, if you are trying to find out whether a sugar cube dissolves faster in cold water or warm water, the size of the sugar cube could affect the results. You can weigh the sugar cubes, but you cannot be sure that there are exactly the same number of sugar crystals in each sugar cube.

If the plant in soil A grew better, you would say that your hypothesis was correct. Then you would say that ivy plants grow better in soil A. You cannot talk about all plants, though, because you only looked at ivy plants. Then you might suggest that you do a similar experiment with a spider plant. For sources of error, you might say that one plant might have been healthier than the other plant when you began the experiment.

#7: Repeat your work

Everyone will make mistakes. Sometimes they are your fault and other times they are things that you cannot control. A scientist needs to make sure that his or her results are correct before telling the world what has been discovered. Therefore, you should do your experiment again to make sure that you get the same results. When scientists publish their discoveries in magazines, they always tell people exactly how they did their experiment so that someone else can try it to see if they get the same results.

To check your results, you could repeat the entire experiment. You could have started with four plants: two plants in soil A and two plants in soil B. In this case, you would have been repeating the experiment while you were doing it the first time.

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