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Why Wet Sand Builds Castles and Dry Sand Slumps

6th grade nonfiction passage about sand and water: 224 words, six questions, an answer key and vocabulary.

6th grade nonfiction sand and water 224 words

Why Wet Sand Builds Castles and Dry Sand Slumps

Pour a bucket of dry sand onto a beach and it makes a low, flat hill. Try to carve a tower from it, and the walls crumble right away. Wet sand behaves very differently. You can pack it into a bucket, flip it over, and lift the bucket away to reveal a sturdy turret with sharp edges.

The difference comes from water. Each grain of sand is a tiny, hard bit of rock or shell, and dry grains slide past one another easily. Little holds them together, so a steep pile slips and spreads out.

When sand is damp, a thin film of water coats every grain. Where two grains touch, the water gathers into a tiny curved bridge. Water molecules like to stay close together, a pull known as surface tension, so each bridge tugs the grains toward each other. Millions of these small bridges add up to a surprisingly strong grip.

Builders at sandcastle contests know there is a limit, though. If the sand is soaked, the water fills all the gaps and the bridges disappear. The grains float apart and the mixture flows like thick soup. The best castles come from sand that is wet enough to stick but not so wet that it runs. As a castle dries in the sun, the bridges shrink away and the walls slowly crumble.

Questions

  1. What happens to a tower carved from dry sand? in the text

  2. What forms where two damp grains of sand touch? in the text

  3. What is the pull that keeps water molecules close together called? in the text

  4. What happens when sand is soaked with too much water? in the text

  5. Why does a sandcastle slowly crumble as it dries in the sun? think about it

  6. Why might a builder add water to sand a little at a time? think about it

Words to know

grain
one tiny, hard piece of something, like sand
surface tension
the pull that keeps water molecules close together
sturdy
strong and not likely to fall apart
crumble
to break into small pieces
soaked
made completely wet all the way through
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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 · 195 words · Flesch-Kincaid grade 2

Pour dry sand on a beach. It makes a low, flat hill. Try to carve a tower from it. The walls crumble right away. Wet sand is not like that. You can pack it in a bucket and flip it over. Lift the bucket, and a sturdy tower stands there with sharp edges.

Water makes the difference. Each grain of sand is a tiny, hard bit of rock or shell. Dry grains slide past each other easily. Little holds them together. So a steep pile slips and spreads out.

Damp sand is different. A thin film of water coats each grain. Where two grains touch, the water makes a tiny curved bridge. Water likes to stay close together. This pull is called surface tension. Each bridge pulls the grains toward each other. Millions of bridges make a strong grip.

There is a limit, though. If sand is soaked, water fills the gaps. The bridges disappear. The grains float apart, and the sand flows like thick soup. The best castles use sand that is wet enough to stick but not too wet. When a castle dries in the sun, the bridges shrink, and the walls crumble.

▲ This passage · 224 words · Flesch-Kincaid grade 5.5

Pour a bucket of dry sand onto a beach and it makes a low, flat hill. Try to carve a tower from it, and the walls crumble right away. Wet sand behaves very differently. You can pack it into a bucket, flip it over, and lift the bucket away to reveal a sturdy turret with sharp edges.

The difference comes from water. Each grain of sand is a tiny, hard bit of rock or shell, and dry grains slide past one another easily. Little holds them together, so a steep pile slips and spreads out.

When sand is damp, a thin film of water coats every grain. Where two grains touch, the water gathers into a tiny curved bridge. Water molecules like to stay close together, a pull known as surface tension, so each bridge tugs the grains toward each other. Millions of these small bridges add up to a surprisingly strong grip.

Builders at sandcastle contests know there is a limit, though. If the sand is soaked, the water fills all the gaps and the bridges disappear. The grains float apart and the mixture flows like thick soup. The best castles come from sand that is wet enough to stick but not so wet that it runs. As a castle dries in the sun, the bridges shrink away and the walls slowly crumble.

■ Harder · 267 words · Flesch-Kincaid grade 7.6

Pour a bucket of dry sand onto a beach and it settles into a low, flat hill. Try to carve a tower from it, and the walls crumble almost as soon as you shape them. Wet sand, on the other hand, behaves in a completely different way. You can pack it firmly into a bucket, flip the bucket over, and lift it away to reveal a sturdy turret with crisp, sharp edges.

The difference comes entirely from water. Each grain of sand is a tiny, hard bit of rock or shell, and dry grains slide past one another with very little resistance. Because almost nothing holds them together, a steep pile of dry sand slips downward and spreads outward.

When sand is damp, a thin film of water coats every grain. At each point where two grains touch, the water gathers into a tiny curved bridge. Water molecules prefer to stay close together, a pull known as surface tension, so every bridge tugs the neighboring grains toward each other. Millions of these small bridges add up to a surprisingly strong grip across the whole structure.

Experienced builders at sandcastle contests understand that this effect has a limit. If the sand is soaked, the water fills every gap between the grains and the bridges disappear altogether. The grains float apart, and the mixture flows like thick soup. The best castles are made from sand that is wet enough to stick but not so wet that it runs. Later, as the castle dries in the warm sun, the bridges gradually shrink away, and the walls slowly begin to crumble.

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 grain, surface tension, sturdy, crumble and soaked 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 Wet Sand Builds Castles and Dry Sand Slumps"?

It was written for 6th grade. It has 224 words and works out to a Flesch-Kincaid grade level of about 5.5. 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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