ChemistryChoosing the Right Material for a Job
Atlas stands in a cozy workshop filled with shelves of boots, windows, umbrellas, and cups, holding up a shiny glass jar in one hand and a squishy rubber boot in the other, grinning as he compares the two very different materials.
- Identify at least two properties of a material, such as hard, soft, clear, or waterproof.
- Tell why a material is a good match for a specific job.
- Compare two materials and decide which one is better for a given use.
- Guess what might happen if the wrong material were used for a job.
Key terms
- material
- the stuff an object is made from, like glass, rubber, or cotton
- property
- something you can observe about a material, like clear or waterproof
- waterproof
- a property that means water cannot get through the material
- clear
- a property that means you can see right through the material
Materials Have Properties
Every material is made of stuff with its own special properties, and a property tells us what the material is like. Glass is clear and hard, rubber is bendy and waterproof, and cotton is soft and soaks up water. By noticing these properties, you can describe each material carefully. Properties are the clues that help you decide which material is the best fit for any job you need done.
Matching Material to the Job
We choose a material because its properties match what the job needs. A window must let you see through it, so we pick glass because glass is clear. A rain boot must keep your feet dry, so we pick rubber because rubber is waterproof. A soft t-shirt should feel comfy, so we pick cotton. Thinking about the job first makes it easy to choose the right material.
When the Material Is Wrong
If you pick a material whose properties do not match the job, things go wrong. A boot made of cotton would soak up water and leave your feet wet, because cotton is not waterproof. A window made of rubber would be useless because you could not see through it. A glass boot would crack the moment you walked. The wrong properties mean the object cannot do its job.
Worked examples
Choose the best material for an umbrella that keeps rain off.
- The job is to block rain, so the material must keep water out.
- Think about properties: which material is waterproof?
- Rubber or coated cloth is waterproof, while cotton soaks up water.
Answer: A waterproof material like rubber or coated cloth is best because it keeps the rain out.
Activity
Drag each material to the job it is best for.
Practice
Compare glass and rubber and tell which is better for a window.
Predict what would happen if a cup were made of paper.
Common mistakes to avoid
- Any material works for any job.Each job needs a material whose properties match, like waterproof rubber for boots that keep feet dry.
- Cotton keeps water out like rubber does.Cotton soaks up water instead of blocking it, so it would leave your feet wet, unlike waterproof rubber.
Check your understanding
Why is glass a good material for a window?
A child needs boots to walk in a puddle. Which material is the best choice?
What would happen if someone made a rain boot out of cotton?
Recap
Every material has special properties like clear, soft, or waterproof, and we pick a material because its properties match the job. Choosing the wrong material, like a cotton boot, means the object cannot do what it is supposed to do.
Reflect
What material would you choose to build something special, and why?