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## Chapter 18

### Part 1: Home and School Investigation

Send the Letter to Family (PDF file) home with each child. Once they have brought in their pictures, pair the children. Have them share their pictures with each other and talk about the number of cups they used. You might want to sort the pictures by number of cups. A good time to do this activity is after Lesson 2 on cups, pints, and quarts.

### Part 2: Be an Investigator

A good time to do this investigation is after Lesson 1 on comparing and ordering capacity.

#### Materials

• clear cylindrical glass
• water
• strip of cardboard

#### Introducing the Investigation

Ask children what happens to puddles of water on the ground. Why don't they just stay there? Get children talking about how the hot sun dries them up. Introduce the term evaporation and talk about how water becomes part of the air.

Show children the glass. Tell them you are going to fill it with some water. Each day you will measure how much water is left in the glass. Hold a strip of cardboard up to the base of the glass. Mark the water level on the strip of cardboard. Each day you will ask the children to predict where the mark will be the next day.

#### Doing the Investigation

Rates of evaporation vary from place to place. You may want to do the measuring every few days or once a week to get a noticeable difference in the water level.

Continue this investigation until the water is gone.