Same Science › Planning investigations › Writing a hypothesis
How do kids write a hypothesis?
A hypothesis is a testable prediction with a reason. Most classes use a three-part frame: If [I change this], then [this will happen to what I measure], because [science reason]. “If plants get more light, then they will grow taller, because plants use light to make food.” It's not a guess: it has to be testable and have a reason.
- If: what you'll change (the independent variable).
- Then: what you predict will happen to what you measure.
- Because: the science reason behind the prediction.
Why schools teach it
Predictions you can actually test
NGSS asks students to ask questions and plan investigations (science practices 1 and 3). A hypothesis links the question to the experiment: it names what will change and what will be measured.
The “because” keeps it from being a wild guess, and the frame makes the variables obvious, which sets up the fair test.
At the kitchen table
What to say, and what to skip
Say this
What will you change?
That goes after “If.”What will you measure, and what do you think will happen to it?
That goes after “then.”Why do you think so?
That's the “because.”Could you test it with an experiment?
Skip this
- Saying a hypothesis is “an educated guess.”It's a testable prediction with a reason.
- Hypotheses that can't be tested.“Blue is the best color” is an opinion.
- Treating a wrong hypothesis as a failure.Data that disproves a hypothesis is still a result.
See it in action
Question: does salt make ice melt faster?
If
If we sprinkle salt on ice,Then
then it will melt faster than ice with no salt,Because
because salt lowers the temperature at which water freezes.
Now the variables are clear: change salt, measure melting time.
Free practice sheet
Make a hypothesis sheet
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Parents also ask
Is a hypothesis just a prediction?
A prediction plus a reason. The “because” is what makes it a hypothesis.
What if the experiment proves it wrong?
Then you learned something. Scientists report results either way.
Does it always need “because”?
Many classes require it from about fourth grade. Some younger classes use just If… then…
Can a hypothesis be a question?
No. The question comes first; the hypothesis is the testable answer.