What Is Thermal Contraction? — Reading Comprehension

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Grades

Standards

MS-PS3-4
4-PS3-3
4-PS3-2

About This Reader

This middle school science passage introduces the concept of thermal contraction, aligned with NGSS standard MS-PS1-4. It explains how materials shrink when they lose heat and how the particles inside them move closer together. The passage gives real-world examples like power lines tightening in cold weather and cracks forming in sidewalks, helping students relate to physical science concepts. It also discusses why engineers must consider thermal contraction when designing roads, bridges, and buildings. This passage builds vocabulary, improves reading comprehension, and supports crosscutting NGSS concepts like structure and properties of matter. It’s a great way to blend science and literacy in the classroom or at home.

CONTENT PREVIEW

Have you ever noticed that metal seems to shrink a little when it gets cold? That’s an example of thermal contraction in action!

Thermal contraction happens when materials cool down and their particles move closer together. As things lose heat, their particles slow down and take up less space. This makes the object shrink slightly.

All materials are made of tiny particles, like atoms or molecules. When something is warm, those particles move around quickly and spread out. But when the temperature drops, the particles lose energy and move more slowly. As a result, they get closer together—and that’s thermal contraction!

One common place you can see this is in power lines. On a hot day, the lines may sag a little because the metal wires expand. But on a cold day, those same wires tighten and look straighter. That’s because the metal contracts as it cools.

Thermal contraction also affects roads, bridges, and buildings. Engineers must plan for it when designing large structures. Without the right gaps or joints, parts can crack or break when the temperature changes suddenly.

It’s the opposite of thermal expansion, where things get larger when heated.

So, the next time you see a tight power line on a cold morning or a small crack in a sidewalk, you might be looking at thermal contraction at work!

Fun Fact: The metal lids on glass jars are easier to open if you run them under hot water. That’s because the metal expands with heat—just the opposite of thermal contraction!

What is thermal contraction?

When materials heat up and expandWhen materials break apartWhen materials cool down and shrinkWhen materials change color

What happens to particles during thermal contraction?

They move faster and spread outThey stop movingThey get biggerThey move closer together

Why do materials shrink when they get cold?

Because they meltBecause the particles lose energy and slow downBecause they freeze solidBecause they gain heat

Which of the following is an example of thermal contraction?

Ice melting into waterPower lines tightening on a cold dayA balloon poppingA sponge soaking up water

What is the opposite of thermal contraction?

Thermal freezingThermal blendingThermal expansionThermal reflection

Why do engineers need to plan for thermal contraction?

To decorate bridgesTo keep lights brightTo prevent cracks or breaks in structuresTo change colors