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Why Salad Dressing Separates in the Bottle

6th grade nonfiction passage about mixtures of oil and water: 231 words, six questions, an answer key and vocabulary.

6th grade nonfiction mixtures of oil and water 231 words

Why Salad Dressing Separates in the Bottle

Shake a bottle of oil and vinegar dressing and it looks like one cloudy liquid. Set it on the shelf for a few minutes, and a golden layer of oil rises to the top while the watery vinegar sinks below. Why won't they stay mixed?

Vinegar is mostly water. Water molecules attract one another strongly, and they do not attract oil molecules nearly as much, so each liquid prefers to stay with its own kind. Oil is also less dense than water, which means a cup of oil weighs less than a cup of water. So when the droplets drift together, the oil floats to the top.

Shaking breaks the oil into tiny droplets scattered through the vinegar. This kind of mixture is called an emulsion, but a plain one is only temporary. The droplets bump together, join into bigger ones, and the layers form again.

Cooks have a fix. Adding a spoonful of mustard or a little egg yolk helps keep the mixture together. These foods contain substances called emulsifiers. Each emulsifier molecule is attracted to oil at one end and to water at the other, so it sits around the droplets like a coat and keeps them from merging. Mayonnaise is a famous example. It is made of oil and a bit of vinegar or lemon juice, held together by egg yolk, and it stays smooth in the refrigerator.

Questions

  1. Which liquid rises to the top when the dressing sits on the shelf? in the text

  2. What does it mean that oil is less dense than water? in the text

  3. What does shaking do to the oil in the bottle? in the text

  4. What is the job of an emulsifier? in the text

  5. Which two foods does the passage name as helping to hold a dressing together? in the text

  6. Why do you think mayonnaise stays smooth while plain shaken dressing does not? think about it

Words to know

dense
heavy for its size because it is packed tightly
droplets
very small drops of liquid
emulsion
a mixture of liquids that normally stay apart
emulsifiers
substances that help oil and water stay mixed
attract
to pull something closer
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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 · 213 words · Flesch-Kincaid grade 3.6

Shake a bottle of oil and vinegar dressing. It looks like one cloudy liquid. Set it on the shelf for a few minutes. A golden layer of oil rises to the top. The watery vinegar sinks below. Why do they not stay mixed?

Vinegar is mostly water. Water molecules pull on each other strongly. They do not pull on oil molecules as much. So each liquid likes to stay with its own kind. Oil is also less dense than water. A cup of oil weighs less than a cup of water. So the oil floats to the top.

Shaking breaks the oil into tiny droplets in the vinegar. This kind of mixture is called an emulsion. But a plain one lasts only a short time. The droplets bump together and join into bigger ones. Then the layers form again.

Cooks have a fix. Add a spoonful of mustard or a little egg yolk. These foods have substances called emulsifiers. One end of each emulsifier molecule is drawn to oil. The other end is drawn to water. So it coats the droplets and keeps them from joining. Mayonnaise is a good example. It is oil with a bit of vinegar or lemon juice, held together by egg yolk. It stays smooth in the refrigerator.

▲ This passage · 231 words · Flesch-Kincaid grade 6.9

Shake a bottle of oil and vinegar dressing and it looks like one cloudy liquid. Set it on the shelf for a few minutes, and a golden layer of oil rises to the top while the watery vinegar sinks below. Why won't they stay mixed?

Vinegar is mostly water. Water molecules attract one another strongly, and they do not attract oil molecules nearly as much, so each liquid prefers to stay with its own kind. Oil is also less dense than water, which means a cup of oil weighs less than a cup of water. So when the droplets drift together, the oil floats to the top.

Shaking breaks the oil into tiny droplets scattered through the vinegar. This kind of mixture is called an emulsion, but a plain one is only temporary. The droplets bump together, join into bigger ones, and the layers form again.

Cooks have a fix. Adding a spoonful of mustard or a little egg yolk helps keep the mixture together. These foods contain substances called emulsifiers. Each emulsifier molecule is attracted to oil at one end and to water at the other, so it sits around the droplets like a coat and keeps them from merging. Mayonnaise is a famous example. It is made of oil and a bit of vinegar or lemon juice, held together by egg yolk, and it stays smooth in the refrigerator.

■ Harder · 251 words · Flesch-Kincaid grade 8.8

Shake a bottle of oil and vinegar dressing vigorously, and it looks like a single cloudy liquid. Set the bottle on a shelf for a few minutes, however, and a golden layer of oil rises to the top while the watery vinegar sinks to the bottom. Why will the two liquids not stay mixed together?

Vinegar is mostly water. Water molecules attract one another very strongly, and they attract oil molecules far less, so each liquid prefers to remain with its own kind. Oil is also less dense than water, which means that a cup of oil weighs less than a cup of water. As a result, when the droplets drift together, the oil floats to the top.

Shaking breaks the oil into tiny droplets that are scattered throughout the vinegar. This kind of mixture is called an emulsion, but a plain one is only temporary. The droplets collide, join together into larger ones, and eventually the separate layers form again.

Cooks have discovered a reliable fix. Adding a spoonful of mustard or a little egg yolk helps hold the mixture together, because these foods contain substances called emulsifiers. Each emulsifier molecule is attracted to oil at one end and to water at the other, so it sits around the droplets like a protective coat and keeps them from merging. Mayonnaise is a famous example. It is made of oil and a small amount of vinegar or lemon juice, held together by egg yolk, and it stays smooth in the refrigerator.

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 dense, droplets, emulsion, emulsifiers and attract 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 6 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 Salad Dressing Separates in the Bottle"?

It was written for 6th grade. It has 231 words and works out to a Flesch-Kincaid grade level of about 6.9. 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. 5 ask for something the text says directly and 1 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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