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Lesson 5 of 9

Using a thermometer well

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5 min

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A thermometer bulb is dipped only halfway into hot water. The reading is too low.

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The bulb touches only the surface.
Step 1 of 4
  1. The bulb touches only the surface.
  2. The reading comes out low.
  3. The bulb sits fully inside the water.
  4. Now the reading is true.

The rule

  • Keep the bulb fully inside what you measure. Then the bulb reads the water, not the air.
  • Do not let the bulb touch the bottom or the side. They can be hotter or colder than the water.
  • Wait until the liquid stops moving. Then it matches the water. Then read.
  • Keep a glass thermometer away from flames. The glass can break.
  • If it breaks, do not touch the pieces. Broken glass can cut you. Tell an adult.

Try the lab to finish this lesson.