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Matter Lab 6-8 / Week 11 / Wednesday
3/6
Week 11 · From Nature to New Materials

Wednesday

Bench Lab: Property tests
// Paper from wood, plastic from oil, glass from sand, steel from iron ore
⏱ about 20 min

Wednesday: Bench Lab: Property Tests

Rocket lines up four squares on a towel: paper towel, foil, a piece of plastic bag and the glass jar lid.

"One drop of water each," he says, eyedropper ready. "Then we see who soaks and who sheds."

Raven holds up a flashlight. "And a light test. And a bend test. What do you notice before we start?"

"The glass is the only one I can see through," Rocket says. "And the only one I cannot bend."

Nova hovers above the squares. "Each test asks one question," she says. "Write the question before you write the answer."

Rocket writes: "Does water soak in? Does light pass? Does it bend without breaking?"

"Good," Raven says. "Now the materials will answer."

Properties decide the job

Engineers choose a material for a job by its properties. A structure can be designed for a function by thinking about each material's properties and how it can be shaped.

Paper towels soak up water. Foil blocks light and bends into any shape. Plastic bags shed water and stretch. Glass lets light through and does not bend.

Today you test those claims yourself. Tomorrow you will see what happens to all these materials after we are done with them.

  • A square of paper towel, a square of foil, a square cut from a plastic bag, and a glass jar or lid
  • A cup of tap water and a spoon or eyedropper
  • A flashlight
  • A towel to work on
  • The Bench Log and a pencil
Safety first
A grown-up cuts the plastic bag square. The student does no cutting.
Handle the glass jar with two hands over the towel. If anything glass breaks, step back and call a grown-up.
Nothing is tasted. Keep the water away from the flashlight.
Wash hands when the tests are done.
  1. Lay the four squares and the glass on the towel, in a row, with a label in front of each.
  2. Water test: put one drop of water on each. Wait one minute. Record soaked in, sat on top, or ran off.
  3. Light test: in a dim spot, shine the flashlight through each material at the wall. Record passes, glows, or blocked.
  4. Bend test: gently fold each square in half and open it. Record bends and stays folded, bends and springs back, or does not bend. Do not bend the glass.
  5. Tear test: with your fingers only, try to tear a corner of each square. Record easy, hard, or will not tear. Skip the glass.
  6. Rinse and dry the squares you can save. Pour the water down the sink.
MaterialWater testLight testBend testTear test
Paper towel
Foil
Plastic bag
Glassnot testednot tested
MATCH THE PROPERTY TO THE JOB
  • Read the question.
  • Tap your answer.
You need a window that lets light through and keeps rain out. Which material fits best?
You need to wrap a sandwich so it stays dry. Which property matters most?
Which of your four materials is made from wood?
Lab checkTrue or false?
Each test asks one question about one property.?
The student bends the glass to test it.?
A material's properties help decide what job it gets.?
Foil and plastic both come from wood.?
WHY THIS EXERCISETesting one property at a time is how engineers compare materials fairly.
Which material in today's lab started as silica sand? Type one word.
WHY THIS EXERCISELinking the material in your hand to its resource is the week's big idea.
Try it
Design a fifth test. Maybe: does it float? Does it crinkle loudly? Does it stay flat after rolling?
Write the question, run the test on the three safe squares, and record the answers.
For a grown-up
The student handles paper, foil, a plastic bag and a glass jar. A grown-up cuts the plastic square and stays close during the glass tests.
Any glass that chips or breaks is cleaned up by a grown-up. The student steps back.
Draw your four squares after the water drop. Show where the drop soaked in, sat on top or ran off.

Careful testing. Tomorrow you will read real government data on what happens to paper, glass and plastic after people use them.

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