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The Goo That Hardens When You Punch It

6th grade nonfiction passage about liquids that act like solids: 232 words, six questions, an answer key and vocabulary.

6th grade nonfiction liquids that act like solids 232 words

The Goo That Hardens When You Punch It

Mix cornstarch with water in a bowl, and you can make a strange goo that seems to break the rules. Poke it gently and your finger sinks in as if it were a thick liquid. Slap it hard, or squeeze it into a ball, and it suddenly feels firm. Open your hand and the ball melts into a puddle again. Some people call this goo oobleck.

Most liquids behave the same way no matter how hard you push them. Water, for example, flows whether you stir it slowly or quickly. A liquid that changes with force, like this goo, is called a non-Newtonian fluid, after Isaac Newton, who studied how ordinary liquids flow.

Scientists are still working out the details of why this happens, but here is the main idea. The goo is not a smooth liquid. It is made of countless tiny grains of starch floating in water. When you press slowly, the grains have time to slide past one another, and the water acts as a lubricant between them. When you hit it fast, the grains cannot move out of the way. They jam together, and the mixture acts like a solid for a moment.

Engineers have experimented with materials that stay flexible until they are hit, such as padding that stiffens on impact. Because the starch can clog drains, cooks and teachers scrape leftover goo into the trash.

Questions

  1. What two ingredients make the goo? in the text

  2. What happens when you slap the goo hard? in the text

  3. What is a liquid that changes when you push it with different force called? in the text

  4. What is the goo made of on a tiny scale? in the text

  5. Why does a quick hit make the goo act like a solid? think about it

  6. Why is water not a non-Newtonian fluid? think about it

Words to know

fluid
a liquid or gas that can flow
starch
a white powder found in foods like corn and potatoes
grains
tiny, hard pieces of something
lubricant
something slippery that helps surfaces slide
impact
a sudden hit or crash
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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 · 219 words · Flesch-Kincaid grade 3.2

Mix cornstarch with water in a bowl. You get a strange goo that seems to break the rules. Poke it gently. Your finger sinks in, as if it were a thick liquid. Slap it hard, or squeeze it into a ball. Now it feels firm. Open your hand, and the ball melts into a puddle. Some people call this goo oobleck.

Most liquids act the same way no matter how hard you push. Water flows whether you stir it slowly or fast. A liquid that changes with force, like this goo, is called a non-Newtonian fluid. The name comes from Isaac Newton, who studied how ordinary liquids flow.

Scientists are still working out the details. But here is the main idea. The goo is not a smooth liquid. It is made of countless tiny grains of starch floating in water. When you press slowly, the grains have time to slide past each other. The water helps them slide. When you hit it fast, the grains cannot move out of the way. They jam together. The mixture acts like a solid for a moment.

Engineers have tried making materials that stay flexible until they are hit. One example is padding that stiffens on impact. The starch can clog drains. So cooks and teachers scrape leftover goo into the trash.

▲ This passage · 232 words · Flesch-Kincaid grade 6

Mix cornstarch with water in a bowl, and you can make a strange goo that seems to break the rules. Poke it gently and your finger sinks in as if it were a thick liquid. Slap it hard, or squeeze it into a ball, and it suddenly feels firm. Open your hand and the ball melts into a puddle again. Some people call this goo oobleck.

Most liquids behave the same way no matter how hard you push them. Water, for example, flows whether you stir it slowly or quickly. A liquid that changes with force, like this goo, is called a non-Newtonian fluid, after Isaac Newton, who studied how ordinary liquids flow.

Scientists are still working out the details of why this happens, but here is the main idea. The goo is not a smooth liquid. It is made of countless tiny grains of starch floating in water. When you press slowly, the grains have time to slide past one another, and the water acts as a lubricant between them. When you hit it fast, the grains cannot move out of the way. They jam together, and the mixture acts like a solid for a moment.

Engineers have experimented with materials that stay flexible until they are hit, such as padding that stiffens on impact. Because the starch can clog drains, cooks and teachers scrape leftover goo into the trash.

■ Harder · 253 words · Flesch-Kincaid grade 7.3

Mix cornstarch with water in a bowl, and you can create a peculiar goo that seems to defy the ordinary rules of liquids. Poke it gently and your finger sinks in as though it were a thick liquid. Slap it hard, or squeeze it into a ball, and it suddenly feels firm. Open your hand, and the ball melts back into a puddle. Some people call this remarkable goo oobleck.

Most liquids behave in exactly the same way no matter how forcefully you push on them. Water, for example, flows whether you stir it slowly or quickly. A liquid whose behavior changes with the amount of force applied, like this goo, is called a non-Newtonian fluid, in honor of Isaac Newton, who studied how ordinary liquids flow.

Scientists are still working out the finer details of why this happens, but the main idea is simple enough. The goo is not a smooth liquid at all. It is made of countless tiny grains of starch floating in water. When you press slowly, the grains have time to slide past one another, and the water acts as a lubricant between them. When you hit it fast, the grains cannot get out of the way in time. They jam together, and for a moment the mixture acts like a solid.

Engineers have experimented with materials that stay flexible until they are struck, such as padding that stiffens on impact. Because the starch can clog drains, cooks and teachers scrape any leftover goo into the trash.

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 fluid, starch, grains, lubricant and impact 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 "The Goo That Hardens When You Punch It"?

It was written for 6th grade. It has 232 words and works out to a Flesch-Kincaid grade level of about 6.0. 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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