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Tweaking things in the PBS science lab

Barby Little, Science Teacher, and the PBS Science Team

How do we learn about something? By doing something to it and observing how it responds!

In the PBS science lab, students learn how to tweak things and see how they change. In this way, they learn about the nature of the things around them.

This is a fun lens through which to look at the world! As your children notice interesting things in the world around them, encourage them to think about what could be changed and what would happen as a result of that change.

The thing we are changing is called the variable. To find out what happens when we change the variable, we have to measure something. As students move up through the grades at PBS, they have increasingly sophisticated experiences with this.


For example, if we have a balloon blown up by a chemical reaction in a bottle, what happens if we use more chemicals? The variable is the amount of chemicals. To measure what happens when make this change, we can measure the size of the balloon. The Kindergarten students tested this in their first weeks of science.

2nd grade

What happens if we soak shells in acid? How is it different if we soak them in water? The variable here is acid versus water. The 2nd-graders conducted this experiment to find out what acid does to teeth. They discovered that acid is able to dissolve shells (and teeth), but plain water didn’t dissolve the shells much.

Then we took our data and applied it to other things we know: The bacteria that grow on our teeth make acid. This is why you want to brush your teeth!

The 2nd-graders also tested the ingredients in toothpaste to see which ones make better cleaners. They stained a tile “tooth” with blueberry juice and then measured the cleaning ability of several different substances. The variable in this experiment was the ingredients. They found that calcium carbonate was the best cleaner. They conducted similar experiments to see which ingredients made the most foam. The results of these experiments helped the students design their own toothpaste formulas.

5th grade

Which forest is more flammable, one with plenty of bushy undergrowth or one that has a clear forest floor? The 5th-graders created a simulation where they burned two different tiny model forests. The variable here was the density of plant growth on the forest floor. They discovered that fire spread much more quickly through a forest with dense undergrowth.

The 5th-graders also measured the flammability of a mixture of water and rubbing alcohol. They changed the ratio of water and alcohol to see what would happen. The variable in this case was the percentage of alcohol in the mixture. They measured whether or not it would burn. They were looking for the tipping point: what was the lowest percentage of alcohol that would still burn?

Bringing it home

You can apply this idea at home as students notice things around them and are curious about them. If they are noticing some interesting plants growing in a yard or school: How is the plant growth different in the shadow of the building vs. further out in the sunshine? One type of car uses more gas than the other. What do they think is different about the car that makes it use more gas?

The world around us is full of fun inquiries that can be explored through the lens of tweaking the variables!

Barby Little has taught students from Kindergarten through college, and topics from art to math and science. She came to PBS only 2 years after its founding, and has been a cherished member of our community ever since. Barby is supported by the rest of the PBS science team, Associate Teacher Erik Romano and consultant Lisa Dettloff, a lifelong science educator with experience at Lawrence Hall of Science, Nueva School, Al Gore’s Climate Education Project, and Microsoft’s Next Media Research Lab.

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