☰ خطة العام · العلوم (بالإنجليزية)

Wood, sunshine and solar ovens

الأسبوع 22 · المحور الثالث، الوحدة الثالثة: المشروع البيني «الجانب المشمس»: الطاقة الشمسية والطبخ · 3 دروس
3

Design a solar oven

Discovery Education Science P4: Term 2, Unit 3, pp. 84–97
GoalFollow the steps of engineering design to plan, build, test and improve a solar oven that warms a cup of water.
New words
engineer · a person who designs and builds things to solve problemsprototype · the first model of a design, built to be testedblueprint · a detailed drawing that shows how to build something
Explanation

Engineers solve problems with steps. They ask what the problem is, imagine many ideas, plan the best one, build it, test it and improve it. Our problem: warm a cup of water using only sunshine. Imagine three sketches, then choose one. In the plan, draw the side view and the top view and label the parts: a reflector to send light in, a dark absorber to turn light into heat, and a clear cover to trap heat. A team shares the jobs: a captain who encourages everyone, a materials manager, a chief engineer who keeps building safe, and a reporter who writes down each step. After building, test it, measure the temperature, and ask: did it work as we expected? What would make it better? Every good engineer improves the first design, because the first try is rarely the best.

Worked examples
JobMaterial chosen
reflectorfoil
absorberblack paper
coverclear plastic wrap
Omar’s team chooses materials from the tests. For the reflector they pick foil, for the absorber black paper and for the cover clear plastic wrap. They pick the best material for each job.
TimeWater
start21 °C
after 30 minutes38 °C
The team tests its prototype for 30 minutes. The water goes from 21 °C to 38 °C. The rise is 38 − 21 = 17 °C. They expected more, so they ask why.
Problem solving: the lid is fogging up and the foil has slipped down. The team fixes one problem at a time. They tape the foil, wipe the lid and test again. The new rise is 22 °C, so the improvement worked.
Class activity

Design a solar oven (a grown-up cuts the box and handles hot water). Sketch three ideas on paper. Pick one and draw a blueprint with side and top views; label the reflector, absorber and cover. Build it from a box, foil, black paper and plastic wrap. Test it in the sun for 30 minutes with a cup of water and write the start and end temperatures. Then write one thing to improve. Never look at the foil’s shine, and this oven only warms water: it is not for cooking food.

Practice
1
Put the steps in the right order: test, plan, ask, build, imagine, improve.
2
The water was 20 °C at the start and 35 °C at the end. What was the rise?
3
Which sample would make the best reflector for a solar oven? Say the letter.
ABC
4
Name one job for each team member: captain, materials manager, chief engineer, reporter.