Week 8 · Axis 1, Chapter 3 Get Fit with Healthy Eating (C) · 3 lessons
1
Zeer pots and refrigerators
Discover P3 Term 1: Axis 1, Chapter 3
GoalExplain how a refrigerator and a zeer pot keep food cold, and sketch two cold-keeping containers.
New words
refrigerator · a machine that uses electricity to keep food coldzeer pot · a cooler made of two clay pots with wet sand between themevaporate · to change from liquid water into a gas in the airfeedback · kind comments that help improve a design
Explanation
Cold helps food stay good for longer. A refrigerator uses electricity to keep its inside cold. A very long time ago, before there was electricity, people found other ways. One way is the zeer pot, which people have used in Egypt and in other hot, dry places. Put a small clay pot inside a bigger clay pot. Fill the space between them with sand, and pour water into the sand. Slowly the water dries out of the wet sand and becomes vapour in the air. When water evaporates it takes some heat with it, so the inside of the pot gets cooler. A zeer works best in the shade, where there is a breeze and the air is dry. In the sun it warms up quickly. To design your own cold container, sketch two ideas, share them with another team, and use the traffic-light feedback: red for a suggestion, yellow for what is confusing, green for what works best.
wet sand→water evaporates→heat is taken away→inside is cooler
Worked examples
A farm family in a dry village keeps milk and cheese in a zeer pot in the shade. Mariam’s grandmother pours water on the sand every morning, and the food stays cooler than the air outside.
Place
Result
Shade, with a breeze
cooler food
Hot sun
warm food
Where should the zeer pot stand? Karim tries two places. In the shade with a breeze: the food stays cool. In the hot sun: the sand dries and warms up quickly. The shady breezy place is better.
Seif sketches two ideas: Idea 1, a box with wet cloth around it. Idea 2, two buckets with damp sand between them. His partner gives traffic-light feedback: green—the damp sand is a good idea; yellow—I do not understand the lid; red—add a cover to keep out dirt.
Class activity
Sketch two ideas for a container that keeps canteen food cold, using things you could really find (a box, cloth, sand, a pot, newspaper). Label every part with its material. Show them to a partner. They give you red, yellow and green feedback. Circle the feedback you will use.
Practice
1
Before there was electricity, how did people in hot places keep food cool?
They used ideas such as the zeer pot with wet sand.
2
What is a zeer pot made of?
Two clay pots, sand between them, and water.
3
Which place is best for a zeer pot? Say the letter.
B, the breeze. A zeer works best in the shade with a breeze and dry air; the Sun and fire would warm it.
