The Scientific Method (more kitchen science)

[science_spot]

Scientists don't just start fiddling around with things, just to "see what happens".  Well, sometimes, we do, but that's just for fun.  When we get down to business, we have a set method of doing things.... the Scientific Method!

One of my favorite website for science experiment help is http://www.sciencebuddies.org/, and it's not just for the experiment ideas, but for the background information as well.  This site goes beyond giving a simple idea for a science fair experiment.  They give a variety of resources, including their forums, that allow the kids to actually master their experiment while learning the details of the Scientific Method.  The image below, from their site,  shows a diagram of the method, and I'll go into a little more detail below.

 

Ask a Question.  The Scientific Method ALWAYS starts with a question.  You MUST ask a question that you would like to answer with your experiment.  Just "seeing what will happen" is not a question.  A more detailed question is better than a vague one. Let's work through an example.  Will using dilute coffee to water my houseplants make them grow faster than using plain water?

 

Do background research.  Here is where you will do a little research to see if anyone has already answered your question.  If so, you may decide to confirm their findings, or ask a different question, possibly building upon the information their work has provided.  Let's say someone has already performed an experiment to answer this question, but we don't agree with the design of their experiment, so we decide to try to answer this question anyway.

 

Construct a hypothesis.  The hypothesis is your educated guess of what you think will happen.  You want to word it in a way that you can test, take measurements, and answer your original question.  A bad hypothesis would be "it doesn't matter" or "it will make them grow tall" because they are not specific enough.  A good hypothesis is something like "Watering my plants with weak coffee instead of water will have no effect on the growth rate of the plants." or "Watering my plants with strong coffee will increase their growth rate over those that are watered with rainwater."

 

Perform the experiment.  First you will need to design the experiment and set it up.  Here we will want to define what plants to use, how many plants to use in each group, and how many experimental groups we need.  We will want one group fed with rainwater and at least one group fed with dilute coffee.  We could try two different concentrations of coffee if we wanted to, setting up one group for each coffee concentration.  The key to a good experimental design is to have only one variable.  In this case the variable will be the substance used to water the plants.  So we want to make sure we give each plant the same amount of water (or dilute coffee), and on the same days.  We also want to make sure that each plant started at the same height (or from seed), each plant gets the same amount of sun, is planted in the same soil, gets water at the same temperature, etc.  For our experiment, we may use the following scheme:

Group 1 - 3 plants, each fed with 1/2 cup room temperature water 2x per week for 8 weeks.

Group 2 - 3 plants, each fed with 1/2 cup strong coffee at room temperature 2x per week for 8 weeks.    Strong coffee will be brewed fresh that morning using double the beans called for in the directions.  Allow to sit until it reaches room temperature before watering the plants.

Group 3 - 3 plants, each fed with 1/2 cup weak coffee at room temperature 2x per week for 8 weeks.  Weak coffee will be brewed fresh that morning using half the beans called for in the directions.  Allow to sit until it reaches room temperature before watering the plants.

When designing the experiment, we need to have a method to show the results.  Measurements with numbers are always preferred to general descriptions.  In this case, we will measure the height of the plants.  We can measure as often as we want to, or just measure the endpoint (at the8 week close of the experiment).  Record your measurements on a paper, and any additional comments you have (such as the leaves turning brown, or the plant appearing to die or get dry).

 

Analyze the results.  Once you have all your measurements, you can analyze your data in order to see the results of your experiment and determine if your hypothesis is correct or not.  In our case, say we have recorded the following data:

Group 1 measurements:

Week 4 - plant 1 = 6", plant 2 = 7", plant 3 = 7 3/4"

Week 8 - plant 1 = 7", plant 2 = 9", plant 3 = 11"

 

Group 2 measurements:

Week 4 - plant 1 = 4", plant 2 = 6", plant 3 = 5 1/2"

Week 8 - plant 1 = 5", plant 2 = 6", plant 3 = 6"

 

Group 3 measurements:

Week 4 - plant 1 = 7", plant 2 = 6", plant 3 = 9"

Week 8 - plant 1 = 8", plant 2 = 9", plant 3 = 10"

 

Although we recorded measurements at 4 weeks, we aren't going to use them. We'll average the measurements for the three plants of each group to get the following data:

Group 1 average = 9"

Group 2 average = 5.7"

Group 3 average = 9"

 

So it turns out that the weak coffee group and water group were grew to the same size!  We also showed that the group watered with strong coffee didn't grow as fast.  So if we return to our hypothesis (in purple, above), we can say that our hypothesis is true!  If it were not true, that would still be okay, because we learned something whether our guess (hypothesis) was correct or not. If it was not correct, we could use what we learned to design a new hypothesis and experiment in order to learn more.

 

Report your results. Often scientists write journal publications in order to share their experiment and results with others so everyone can learn from the experiment.  Students often do the same thing, either in a published paper or a poster contest or science fair.

 

So you can see the method scientists use to ask questions, design experiments, and report results is described very well.  This method has been proven to work in a wide variety of experimental types and scientific disciplines.  Once you get the hang of it, it's really easy to follow, too.

Once we get back to "science fair season", I encourage you to come back to this post for help designing your experiments and projects.  If you need more help, check out my group, The Science Spot, or the Science Buddies website.  But you don't have to wait until a science fair project is announced.... you can ask a question and test your hypothesis anytime you want, right in your kitchen.  Happy experimenting!

 

Tonya

AKA sunmoonstars

The Science Spot

 

[MotherofIreland]

Jul. 10, 2009 at 2:08 PM

Awesome! Thank you!!