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Why Bridges Have Gaps in the Road

5th grade nonfiction passage about heat makes solids grow: 218 words, six questions, an answer key and vocabulary.

5th grade nonfiction heat makes solids grow 218 words

Why Bridges Have Gaps in the Road

Drive across a long bridge and you may feel a bump as the tires cross a strip of metal with jagged teeth. Those strips fill gaps in the road, and they are called expansion joints. The reason for them is heat.

Nearly all solid materials grow a tiny bit larger when they warm up and shrink a tiny bit when they cool down. Inside the steel and concrete, the atoms jiggle faster when they are warm, so they push a little farther apart. A bridge on a hot summer afternoon is slightly longer than the same bridge on a freezing winter night. For a long bridge, the change is enough to measure with a ruler.

Without a gap, the road would have no room to grow. Its ends would shove against each other with great force, and the slabs could buckle or crack. The gap gives the bridge space to stretch in summer and shrink in winter. Many bridges also rest one end on rollers or sliding plates, so that the whole span can move a little without any strain.

An old railroad sound comes from the same idea. Tracks were once laid in short pieces with small spaces between them. The wheels went clickety-clack over each space, and the spaces let the hot metal grow safely.

Questions

  1. What are the metal strips in a bridge road called? in the text

  2. What happens to most solid materials when they warm up? in the text

  3. Why do warm materials grow? in the text

  4. When is a bridge slightly longer, on a hot afternoon or a freezing night? in the text

  5. Why would a road with no gaps be in trouble on a hot day? think about it

  6. Why were old railroad tracks laid with small spaces between the pieces? think about it

Words to know

expansion
growing larger or taking up more room
atom
a tiny building block of all matter
buckle
to bend or bulge out of shape
slab
a flat, thick piece of hard material
strain
a pressure that pulls or pushes too hard
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One passage, three levels

The same topic and facts written three ways, so a mixed class can read and talk about one text. Each group’s sheet shows only a shape; the key says which is which.

● Easier · 197 words · Flesch-Kincaid grade 2.7

Drive over a long bridge and you may feel a bump. The tires cross a strip of metal with teeth. The strip fills a gap in the road. It is called an expansion joint. It is there because of heat.

Most solid things grow a tiny bit bigger when they get warm. They shrink a tiny bit when they get cool. The atoms inside jiggle faster when it is warm, so they push a little farther apart. A bridge on a hot summer day is a bit longer than on a freezing winter night. On a long bridge, you could measure the change with a ruler.

If the road had no gap, it would have no room to grow. Its ends would push on each other hard. The slabs could bend up or crack. The gap gives the bridge room to stretch in summer and shrink in winter. Many bridges also rest one end on rollers, so the bridge can move a little.

Old train tracks did the same thing. They were made of short pieces with small spaces between them. The wheels went clickety-clack over each space. The spaces let the hot metal grow safely.

▲ This passage · 218 words · Flesch-Kincaid grade 5.4

Drive across a long bridge and you may feel a bump as the tires cross a strip of metal with jagged teeth. Those strips fill gaps in the road, and they are called expansion joints. The reason for them is heat.

Nearly all solid materials grow a tiny bit larger when they warm up and shrink a tiny bit when they cool down. Inside the steel and concrete, the atoms jiggle faster when they are warm, so they push a little farther apart. A bridge on a hot summer afternoon is slightly longer than the same bridge on a freezing winter night. For a long bridge, the change is enough to measure with a ruler.

Without a gap, the road would have no room to grow. Its ends would shove against each other with great force, and the slabs could buckle or crack. The gap gives the bridge space to stretch in summer and shrink in winter. Many bridges also rest one end on rollers or sliding plates, so that the whole span can move a little without any strain.

An old railroad sound comes from the same idea. Tracks were once laid in short pieces with small spaces between them. The wheels went clickety-clack over each space, and the spaces let the hot metal grow safely.

■ Harder · 228 words · Flesch-Kincaid grade 7.3

Drive across a long bridge and you may feel a distinct bump as the tires roll over a strip of metal with jagged teeth. Those strips fill deliberate gaps in the roadway, and engineers call them expansion joints. The reason behind them is heat.

Nearly all solid materials grow a tiny bit larger as they warm up and shrink a tiny bit as they cool down. Inside the steel and concrete, the atoms vibrate faster when they are warm, which pushes them slightly farther apart. Consequently, a bridge on a scorching summer afternoon is a little longer than the very same bridge on a freezing winter night. For a long bridge, the difference is large enough to measure with an ordinary ruler.

Without a gap, the roadway would have nowhere to expand. Its ends would shove against one another with tremendous force, and the concrete slabs could buckle or crack. The gap provides space for the bridge to stretch in summer and shrink in winter. Many bridges also rest one end on rollers or sliding plates, so that the entire span can shift a little without suffering any strain.

An old railroad sound comes from the same principle. Tracks were once laid in short pieces with small spaces between them. The wheels rattled clickety-clack over each space, and those spaces allowed the heated metal to grow safely.

Download as one PDF

How to use it

  1. Press Read it big (or B) to put the text on the projector, or Full screen (F) to fill the whole screen.
  2. Ask the questions one at a time and use Show answer when the class has decided. A shows or hides every answer.
  3. Print student copy for the class, or Print with answers for yourself.

Ideas for class

  • Before reading, put expansion, atom, buckle, slab and strain on the board with their meanings from the Words to know section and have students predict what the text will be about.
  • Read it aloud once while students follow along, then have them reread it alone or with a partner. At a calm 100 words a minute it takes about 2 minutes to read aloud.
  • Use the Read it big button (or B) to put the text on the projector, and Show answer on one question at a time so the class commits to an answer first.
  • Question 5 asks the reader to infer. Ask students to point to the words in the passage that led them to their answer.
  • Ask students to write one question the passage did not answer, then look for the answer in a book or on a classroom screen.
  • Print the student copy for independent work and keep the answer-key copy for yourself.

Related

Questions

What reading level is "Why Bridges Have Gaps in the Road"?

It was written for 5th grade. It has 218 words and works out to a Flesch-Kincaid grade level of about 5.4. That is a formula's estimate from sentence length and syllables, and it is not a Lexile or a guided reading level, so check it against your students.

What do the questions ask?

There are six. 4 ask for something the text says directly and 2 ask the reader to work something out from clues. Each has an answer in the key, and the answers are written as a teacher would accept them, not as the only possible wording.

How long does it take to read?

About 2 minutes read aloud at 100 words a minute. For a one-minute fluency check, paste it into the fluency timer and use the word count.

Can I print it?

Yes. Print student copy gives the passage, the questions with lines to write on, and the word meanings. Print with answers gives the same page with the answers filled in. Both are made in your browser.

Is this passage from a published book?

No. It was written for Peabody Teach, so there is no book to buy and no login to read it.

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