Science · Level 1 · 165 words

How Soap Cleans

Original passage © Studio AM, written for Fluency.

Water alone does not wash away oil. Try it. Rub a little cooking oil on your hands and hold them under the tap. The water runs off, and the oil stays. Water and oil do not mix. They pull away from each other.

Soap solves this problem. Every piece of soap is made of tiny parts with two ends. One end loves water. The other end loves oil. When you wash, the oil-loving ends push into the drop of grease and hold on. The water-loving ends point out, away from the grease.

Now the drop of grease is wrapped in a ball. The outside of that ball loves water, so the water can finally carry it. You rinse, and the grease goes down the drain inside its little package. This is why rubbing matters. Rubbing breaks the grease into small drops, and soap needs small drops to wrap. Soap does not kill the dirt. It simply gives the dirt a handle that water can hold.

Comprehension questions

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4 questions
1. What is the main point of the passage?

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C. Soap works by wrapping grease so that water can carry it away.
The whole passage builds to one idea: soap has a water-loving end and an oil-loving end, so it wraps grease in a package water can hold. The last line says it plainly.

2. According to the passage, why does rubbing matter?

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A. It breaks the grease into small drops that soap can wrap.
The text says rubbing breaks the grease into small drops, and soap needs small drops to wrap. The passage also says directly that soap does not kill dirt.

3. The passage suggests that without soap, grease stays on your hands because

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D. water and grease pull away from each other instead of joining
The first paragraph says water and oil do not mix and pull away from each other. Soap's job is to solve exactly that. Weight, heat, and speed are never mentioned.

4. In this passage, "rinse" means

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B. to wash something with clean water so what is loose runs off
The sentence is "You rinse, and the grease goes down the drain." Something is being washed away by water, not scrubbed, dried, or soaked.

Source: Written for Fluency. Original passage © Studio AM, written for Fluency.