Scientific Method Test Tube Experiment for Kids

Test tube experiments for kids.

This test tube experiment is an easy, fun way to demonstrate the scientific method to lower elementary kids.

No STEM education is complete without a thorough understanding of the scientific method.  The good news is, you can use the scientific method to incorporate almost any of your child’s interests into science.

Does your little one love race cars?  Design an experiment around adding variables to increase the speed of her favorite matchbox car.

Whether they love cooking, ballet, photography or knitting, there’s a way to use science to explore almost anything.

Personally, I love coming up with creative ways to get kids interested in botany and the science of plants.  I think it’s a great way to explore the natural world and teach kids to appreciate what makes nature beautiful and interesting.

Test Tube Experiment

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Recently, we got some test tubes to play around with.  I find them an infinitely useful, open-ended teaching tool and love designing lessons around them.

With gardening season in full swing, I decided to take my homeschoolers outside and cut a few sprigs from our herb garden, and bring them indoors for a little STEM project.

Introducing the Scientific Method to Elementary Students

Of course, the scientific method is the foundation of a child’s entire science-based education all the way through college.

So, the sooner you can get them thinking about how it works, the more they will begin to apply its logic to their everyday lives.

You’ll be amazed at how quickly they start to connect the dots and use it in everything from baking (“What happens if we bake the bread without yeast?” to matchbox cars “Does a heavier, bigger car go faster or slower than a smaller, lighter one?”)

If it’s been a while since you’ve been over it yourself, here’s a quick reminder of the basic steps of the scientific method.  Some curriculums add or subtract steps from this list, but this is the sequence we used.

#1  Observation

Identify a clear observation.  An observation is simply something that you notice about the world around you.  In this case, our observation was cut plants take water from the vase through their stems at different rates.

#2  Question

Ask a question that relates to the observation.  Point out to your students/homeschoolers that in order to use the scientific method, your observation must be testable.  A testable question is one that can be answered using an experiment with a single variable.

For this experiment, our question was Which cut herb will drink the water the fastest?

#3  Hypothesis

Next, it’s time to make a prediction about what you think will happen based on your observations.  This educated guess is called a hypothesis and it’s the basis of all scientific experiments.  In this case, my child’s hypothesis was:

I think the plant with the biggest leaves will drink the water the fastest.

#4  Experiment

This is the fun part.  Design an experiment to test your hypothesis and whether or not your hypothesis is correct.  An experiment is an intentional, controlled procedure to test a hypothesis or demonstrate a scientific phenomenon.  Our experiment was simple:

We placed some cut herbs from the garden into test tubes overnight to see which waterline fell the fastest.

#5  Results

After your experiment is complete, make a note of your results.

A result is the final outcome of your experiment.

In this case, the plant with the biggest leaves drank the water the fastest.

As a homeschooler, you can incorporate some age-appropriate math here if you want (measuring the water line with a ruler for younger kids, for example, or charting out the results on a graph for older ones).

#6  Conclusion

Once your results are in, it’s time to draw a conclusion.  A conclusion is a summary analysis of your results.  Conclusions are not infallible and often result in new questions and new ideas for another experiment.  Our conclusion was

Plants with larger leaves seem to need more water than plants with smaller leaves.

#7 Confirmation

Notice that our conclusion is actually a new hypothesis.  So, you may opt to continue your research by designing a new experiment to confirm your hypothesis.

Confirmation is the retesting of a hypothesis in order to determine if your results are consistent.

Things You Will Need

This experiment is

*test tubes (or small glass jars)

*herb cuttings from the garden or grocery store


1.  Begin by explaining the scientific method (see above).  Discuss each step and its role in the scientific process.

2.  Ask each child what he or she thinks will happen and why.  Which plant will drink the water the fastest?  What reason do they have for making that guess?

3.  Leave the cuttings in a sunny window.

4.  Have fun watching the cuttings “race” to see which one drinks the water the fastest.

5.  Record and discuss your results.  Are there any new experiments you can design based on your observations?

Ideas for variations.

Each experiment should ideally have only a single variable.  A variable is one condition that is applied one or more of the test subjects, but not the others.

In this experiment, our variable was the kind of plant.  But each plant (to the extent that it could be controlled) received the same kind of treatment—same amount and type of water, same sunny spot in the window, ect.

If you’d like to experiment with other variables, here are some ideas.  Remember, you only want to test one variable at a time to avoid confusing results.

-Use the same kind of plant in each test tube, but incorporate an additive.  For example, add asprin to one or more of the test tubes and see if that affects the rate of water consumption.

-Split one or more of the stems lengthwise at the end to increase the stem’s interior exposure to the water.

-Vary the kind or amount of light.  Do the plants under grow lights consume water at a faster, slower or the same rate as those in sunlight?  What about full sun versus partial shade?


Use test tubes to introduce the scientific method.

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