This week I got several e-mails from students (and parents) working on science fair projects. We will take a look at a word that many students, parents and teachers misunderstand. To see what I mean, lets start with an imaginary science project. Let's use a classic, which laundry detergent works best. I have judged quite a few science fairs, and this one always turns up.
Now the teacher says you need a hypothesis. What in the world is that? Many people will tell you that it is an educated guess, so you might think you should guess which one will work the best. A hypothesis is not a guess, but it should be educated. The first thing to do in this project would be to look what really makes the detergents different. Does the color of the bottle make a difference? No. What about the price? No. Then what makes them different? Their ingredients! Look at the label to see what they contain. Oops! No luck there. Most laundry detergents contain very little information about what they contain. The internet provides more useful information though.
After a bit of Google searching, you find a ton of information on the ingredients of the various detergents. The first thing you find is that many of them are very similar. Still, you do find small differences. Now you have something to work with. More searching would give you some information about the properties of the different ingredients.
Notice that up to this point, we have not done any experimenting. For a good project, we need to do quite a bit of research before we do anything else. So now it is time for us to form our hypothesis, right? No, not yet. First, we need to define the subject of our project. "Which Laundry Detergent is the Best" is far too broad a topic. By best, do you mean the cheapest? Or that it works best on stains? What kind of stains? Maybe different detergents work better with different stains. Do you want to try all the detergents in the store? In the interest of time and money, we need to narrow this down quite a bit. For our imaginary project, lets compare detergents with enzymes and those without the enzymes.
Now, we are ready to form our hypothesis, right? No, not yet. Now it is back to the research. We need to find out about these enzymes. Detergents grab onto the oil that holds dirt to your clothes. By attaching to the oil and to the water, it pulls the oil away, releasing the dirt. The problem is that some stains are stuck to the cloth with other things, such as guar gum. This chemical is used as a thickener in all sorts of things you use every day. Read a few labels in your kitchen, and it won't take long to find it.
The enzymes used in detergents are chemicals that attack certain kinds of stains. For example, Tide Deep Cleaning Formula contains a mannanase enzyme that attacks certain carbohydrate based stains, including guar gum. Now we are sufficiently educated to set the goal of our project. It could be something along the lines of "Are detergents with enzymes better at removing carbohydrate based stains?" Now, finally we are ready to form our hypothesis. Based on our research, we could state that we think that an enzyme based detergent would be much better at removing carbohydrate based stains.
Now, does that seem like an educated guess? No, not at all. Instead, it seems that we are stating the obvious. Still, all we have to go on so far is our research. We don't know how much better the enzymes will actually work. The difference may be almost too small to notice. Now it is time to act on our hypothesis by actually doing some experimentation.
So a hypothesis is far from being an educated guess. Instead, it is a tentative explanation for an observation, phenomenon, or scientific problem that can be tested by further investigation.
A scientific hypothesis that survives experimental testing may become part of a scientific theory, another very misunderstood word. Many people think the word theory also means a guess. Now we know that a hypothesis is much more than a guess, and a scientific theory is a big step up from a hypothesis. When a scientist says that he has a theory, it means that the idea has already been researched and tested. That does not mean that new evidence can't disprove the theory, but it does mean that there is a lot of evidence to support that explanation of things.
At this point, if you are forming a hypothesis that I might do your science fair project for you, an experimental e-mail will show that while I am always glad to offer advice, you have to do the work.
Hypotheses, Laws, and Theories - What Do Scientists Do?