Constants in Science: Definition & Examples

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  • 0:03 Constants Are Critical
  • 1:36 An Experiment with Constants
  • 3:16 Lesson Summary
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Lesson Transcript
Instructor: Rachel Torrens

Rachel is a Nurse Practitioner with experience working as a high school teacher, skin surgery center, and as a family NP.

Change is usually considered a good thing. However, in a science experiment, it's really important to not change some things. In this lesson, learn why constants are so critical to sound experimentation.

Constants Are Critical

Mercedes wants to make cookies, but she's not sure which temperature will produce the best-tasting cookies so she decides to experiment. She will cook one batch of cookies at 325 degrees, one at 350 degrees, and one at 375 degrees. Which will be tastiest?

In an experiment, the goal is to answer a specific question. To answer that question, you make one specific change, observe the effects, record the data, and draw your conclusion. The one thing that is changed in the experiment is known as the manipulated variable. The effect this change produces is measured and is known as the responding variable.

To understand the relationship between the manipulated variable and responding variable, it's important for the scientist to keep everything else identical. Why? Because this allows the scientist to know if the one change is causing the effect.

Let's get back to the experiment. Remember, Mercedes wanted to know which cooking temperature makes the most delicious cookies, so she only changed the oven's temperature. Everything else in the experiment stayed the same.

If a scientist conducted an experiment, but changed everything at once, he'd have no idea which change produced the result. For example, if Mercedes changed the oven's temperature, the recipe, the baking sheets, and the cooking time, how would she know which change affected the cookies' outcome?! She could never know because she changed too many things at once. For this reason, a constant, or an unchanging variable, is critical in a science experiment.

An Experiment with Constants

Now, Mercedes is performing an experiment with bubbles. Specifically, she wants to know what bubble mix makes the longest lasting bubble. She makes three bubble mixes using different ingredients. They're in identical jars, so she labels them #1, #2, and #3.

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