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The Odd Water That Saves Pond Fish

8th grade nonfiction passage about why ice floats: 254 words, six questions, an answer key and vocabulary.

8th grade nonfiction why ice floats 254 words

The Odd Water That Saves Pond Fish

On a bitter winter day, a pond can be covered with ice, yet fish and frogs below it may live through the whole season. They owe their survival to a strange habit of water. Almost every other liquid grows denser as it cools, and a solid sinks in its own liquid. Water does not follow this rule all the way down, and that exception changes life in cold places.

As water cools, it grows denser, as other liquids do, until it reaches about four degrees Celsius. Below that, something unusual happens. The tiny particles of water begin to lock into an open, six-sided pattern as the water approaches freezing. This pattern holds the particles slightly farther apart than they were in the liquid. The result is that ice takes up more space than the same amount of liquid water, so ice is less dense and floats.

Imagine what would happen if ice sank. Each winter, ice that formed at the surface would drop to the bottom, and the surface would freeze again and sink in turn. A shallow pond could slowly freeze solid from the bottom up, and little could live there.

Because ice floats, it forms a lid instead. The lid also acts as insulation, slowing the loss of heat from the water beneath it. Water just under the ice stays near the freezing point, while the deepest water stays a little warmer, at about four degrees. In this quiet, dim layer, fish slow down, use little energy, and wait for spring.

Questions

  1. What happens to most liquids as they cool? in the text

  2. At about what temperature is water at its densest? in the text

  3. What does the open, six-sided pattern of ice do to the water particles? in the text

  4. Why does ice float on water? think about it

  5. What could happen to a shallow pond if ice sank? think about it

  6. How does the floating lid of ice help the animals below? in the text

Words to know

denser
packed more tightly, so it has more matter in the same space
particles
the tiny pieces that make up all matter
insulation
a layer that slows the escape of heat
survival
staying alive through a hard time
exception
something that does not follow the usual rule
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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 · 217 words · Flesch-Kincaid grade 4

On a bitter winter day, a pond may be covered with ice. Yet the fish and frogs below can live through the whole season. They are saved by a strange habit of water. Almost every other liquid gets denser as it cools, and its solid sinks. Water does not follow this rule all the way down.

As water cools, it gets denser, like other liquids. This lasts until it reaches about four degrees Celsius. Then something odd happens. As the water nears freezing, its tiny particles lock into an open, six-sided pattern. The pattern holds the particles a little farther apart. So ice takes up more space than the same amount of liquid water. That makes ice less dense, so it floats.

What if ice sank? The ice that formed on top would drop to the bottom. The top would freeze and sink again. A shallow pond could freeze solid from the bottom up, and little could live there.

But ice floats, so it forms a lid. The lid works as insulation. It slows the loss of heat from the water below. The water just under the ice stays near freezing. The deepest water stays a little warmer, at about four degrees. In this quiet layer, fish slow down, use little energy, and wait for spring.

▲ This passage · 254 words · Flesch-Kincaid grade 7.1

On a bitter winter day, a pond can be covered with ice, yet fish and frogs below it may live through the whole season. They owe their survival to a strange habit of water. Almost every other liquid grows denser as it cools, and a solid sinks in its own liquid. Water does not follow this rule all the way down, and that exception changes life in cold places.

As water cools, it grows denser, as other liquids do, until it reaches about four degrees Celsius. Below that, something unusual happens. The tiny particles of water begin to lock into an open, six-sided pattern as the water approaches freezing. This pattern holds the particles slightly farther apart than they were in the liquid. The result is that ice takes up more space than the same amount of liquid water, so ice is less dense and floats.

Imagine what would happen if ice sank. Each winter, ice that formed at the surface would drop to the bottom, and the surface would freeze again and sink in turn. A shallow pond could slowly freeze solid from the bottom up, and little could live there.

Because ice floats, it forms a lid instead. The lid also acts as insulation, slowing the loss of heat from the water beneath it. Water just under the ice stays near the freezing point, while the deepest water stays a little warmer, at about four degrees. In this quiet, dim layer, fish slow down, use little energy, and wait for spring.

■ Harder · 267 words · Flesch-Kincaid grade 8.9

On a bitterly cold winter day, a pond may be sealed beneath a sheet of ice, and yet the fish and frogs underneath can often survive the entire season. They owe their survival to a peculiar behavior of water. Nearly every other liquid becomes denser as it cools, which means that a solid formed from it sinks in the liquid. Water follows this rule only part of the way, and that exception transforms life in cold regions.

As water cools, it becomes denser, as other liquids do, until it reaches roughly four degrees Celsius. Below that point, something unexpected occurs. As the water approaches freezing, its tiny particles begin to lock into an open, six-sided pattern, and this arrangement holds them slightly farther apart than they were in the liquid. As a result, ice occupies more space than the same amount of liquid water, so it is less dense and it floats.

Consider what would happen if ice sank instead. Each winter, ice that formed at the surface would fall to the bottom, and the newly exposed surface would freeze and sink in its turn. A shallow pond might gradually freeze solid from the bottom upward, leaving almost nothing alive inside.

Because ice floats, it forms a protective lid. This lid also serves as insulation, which slows the escape of heat from the water below. The layer just beneath the ice remains close to the freezing point, while the deepest water stays a little warmer, at about four degrees. In that quiet, dim layer, fish become sluggish, spend very little energy, and wait patiently for spring.

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 denser, particles, insulation, survival and exception 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 3 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 4 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 "The Odd Water That Saves Pond Fish"?

It was written for 8th grade. It has 254 words and works out to a Flesch-Kincaid grade level of about 7.1. 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 3 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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