Skip to the content
Peabody TeachFor teachers and grown-ups

Why Ice Floats

6th grade nonfiction passage about water and ice: 215 words, five questions, an answer key and vocabulary.

6th grade nonfiction water and ice 215 words

Why Ice Floats

If you drop an ice cube into a glass of water, it bobs to the top and floats. That may seem ordinary, but it is actually unusual. For almost every other substance, the solid form is heavier than the liquid form and sinks in it. Water is one of the few exceptions.

The reason lies in how water freezes. As water cools, its tiny particles, called molecules, slow down and move closer together. Near the freezing point, however, they begin to lock into a rigid pattern with open spaces between them. The pattern holds the molecules slightly farther apart than they were as a liquid, so frozen water takes up about nine percent more space. The same amount of matter spread over more space is less dense, and less dense things float.

This odd behavior matters for life on Earth. When winter arrives, a pond cools from the top, and ice forms at the surface instead of sinking. The floating layer works like a blanket, slowing the loss of heat from the water below. Fish and other pond animals can survive in the liquid underneath all winter long.

Icebergs float for the same reason. Because ice is only a little lighter than liquid water, about nine tenths of an iceberg stays hidden below the surface.

Questions

  1. Why does an ice cube float in water? in the text

  2. About how much more space does frozen water take up than liquid water? in the text

  3. Where does ice form on a pond in winter? in the text

  4. How does a floating layer of ice help the fish in a pond? think about it

  5. Why is most of an iceberg hidden below the water? think about it

Words to know

molecules
the tiny particles that everything is made of
dense
packed with a lot of matter in a small space
rigid
stiff and not able to bend or flow
surface
the top layer of something
iceberg
a huge chunk of floating ice
exceptions
things that do not follow the usual rule
Share

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 · 198 words · Flesch-Kincaid grade 3.8

Drop an ice cube into a glass of water. It bobs to the top and floats. That may seem normal, but it is not. For almost every other substance, the solid is heavier than the liquid. It sinks. Water is one of the few exceptions.

The reason is in how water freezes. As water cools, its tiny particles, called molecules, slow down. They move closer together. Near the freezing point, they lock into a rigid pattern. The pattern has open spaces in it. So the molecules end up a bit farther apart than in the liquid. Frozen water takes up about nine percent more space. The same matter in more space is less dense. Less dense things float.

This matters for life on Earth. In winter, a pond cools from the top. Ice forms at the surface and does not sink. The floating layer works like a blanket. It slows the loss of heat from the water below. Fish and other pond animals can live in the liquid underneath all winter.

Icebergs float for the same reason. Ice is only a little lighter than liquid water. So about nine tenths of an iceberg is hidden under the surface.

▲ This passage · 215 words · Flesch-Kincaid grade 7.1

If you drop an ice cube into a glass of water, it bobs to the top and floats. That may seem ordinary, but it is actually unusual. For almost every other substance, the solid form is heavier than the liquid form and sinks in it. Water is one of the few exceptions.

The reason lies in how water freezes. As water cools, its tiny particles, called molecules, slow down and move closer together. Near the freezing point, however, they begin to lock into a rigid pattern with open spaces between them. The pattern holds the molecules slightly farther apart than they were as a liquid, so frozen water takes up about nine percent more space. The same amount of matter spread over more space is less dense, and less dense things float.

This odd behavior matters for life on Earth. When winter arrives, a pond cools from the top, and ice forms at the surface instead of sinking. The floating layer works like a blanket, slowing the loss of heat from the water below. Fish and other pond animals can survive in the liquid underneath all winter long.

Icebergs float for the same reason. Because ice is only a little lighter than liquid water, about nine tenths of an iceberg stays hidden below the surface.

■ Harder · 236 words · Flesch-Kincaid grade 8.8

If you drop an ice cube into a glass of water, it bobs to the top and floats. That may seem perfectly ordinary, but it is in fact quite unusual. For almost every other substance, the solid form is denser than the liquid form and therefore sinks in it. Water is one of the very few exceptions to this rule.

The explanation lies in the way water freezes. As water cools, its tiny particles, called molecules, slow down and move steadily closer together. Near the freezing point, however, they begin to lock into a rigid, orderly pattern with open spaces between them. That pattern holds the molecules slightly farther apart than they were in the liquid, so frozen water occupies about nine percent more space. The same amount of matter spread across a larger volume is less dense, and less dense materials float.

This peculiar behavior has enormous consequences for life on Earth. When winter arrives, a pond cools from the top downward, and ice forms at the surface instead of sinking to the bottom. The floating layer acts like a blanket, slowing the loss of heat from the water beneath it. Fish and other pond animals are able to survive in the liquid below throughout the entire winter.

Icebergs float for precisely the same reason. Because ice is only slightly lighter than liquid water, about nine tenths of an iceberg remains hidden beneath the surface.

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 molecules, dense, rigid, surface, iceberg and exceptions 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 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 "Why Ice Floats"?

It was written for 6th grade. It has 215 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 five. 3 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.

Nothing you do here is sent to us. No sign-in, no ads.