Start with the job
Do not start with a material you like. Start by saying what the thing has to do.
Step 1: Something to Notice
Watch first. The explanation comes later.
Nobody decides windows should be glass. They decide a window must let light in and keep rain out — and then there is only one material left.
How would you work out what to make something from, if you had never seen one?
Step 2: Find Out
Choose a purpose. Watch which columns get marked as needed.
Step 1 — Predict
A window has to let light through AND keep rain out. Which material does both?
Choose what you think will happen. You cannot see the experiment until you do — guessing first is what makes it worth watching.
Step 3: So Here Is Why
Now the explanation, after you have seen it happen.
Then the properties
Turn the job into properties. Keeps rain off means waterproof. Lets you move means bendy.
Then find a material
Keep only the materials that pass every test. Cardboard is bendy but not waterproof.
Sometimes two materials
A saucepan is metal to carry heat. Its handle is wood so it does not. Two jobs, two materials.
Step 4: A Common Mistake
Lots of people think
“Windows are glass because that is what windows are made of.”
Step 5: Why Saucepans Have Wooden Handles
The same idea somewhere new.
The pan has to take heat, so it is metal. The handle has to NOT take heat to your hand, so it is wood or plastic. One object, two jobs, two materials.
Step 6: Think It Through
Practice makes it stick.
The Raincoat
Problem 1 of 1
A raincoat has to keep water out and bend when you move. Which material?
The Right Material
1 of 3
What do you start with when choosing a material?
2 of 3
Which material for a window?
3 of 3
Match each job to the material that suits it.
Tap a card on the left to start.
Step 7: Quick Check
Show what you know.
Question 1 of 1
Why are windows made of glass?
What You Found Out
- Start with what the job needs.
- Find the properties, then find the material.
- Sometimes one object needs two different materials.
For the grown-up
Start with the job — Ask what the thing has to do before choosing what to make it from. A raincoat must keep water out. A window must let light through. The job decides which properties matter.
No material is best at everything — Glass is clear and breaks. Metal is strong and heavy. Plastic is light and does not last as long outdoors. Choosing means deciding which property matters most for this job.
Start with the job — Do not start by picking a material you like. Start by saying exactly what the thing has to do. A raincoat has to keep rain off you and still let you move your arms. Until you have said that, you have nothing to choose against.
Then the properties — Turn the job into a list of properties. "Keeps rain off" means waterproof. "Lets you move" means bendy. Now you have two tests you can run on any material, instead of a feeling about which one seems right.
Then find a material — Go through the materials and keep only the ones that pass every test on your list. Plastic is waterproof and bendy, so it stays. Cardboard is bendy but not waterproof, so it goes. The list does the choosing for you.
Sometimes two materials — Sometimes one object has two jobs that need opposite properties. A saucepan must carry heat into the food, so the pan is metal. The handle must not carry heat into your hand, so it is wood or plastic. One object, two jobs, two materials.