Science and Technology K–6 · Year 4
How much can a strip hold? Testing paper, plastic, fabric and foil
Science understanding: Chemical sciences
The idea
Materials differ in strength and stretch, which can be measured by loading a strip until it breaks, and those properties decide what a material is used for.
What you need
- strips 2 cm wide and 20 cm long cut from: printer paper, a plastic shopping bag, cotton fabric, aluminium foil, baking paper
- a clamp or two heavy books to hold the top of the strip at the bench edge
- a small plastic cup with a string handle as the load hanger, plus 20 g masses (or 20 g bags of sand) up to 1 kg
- ruler
- a tray under the hanger
How to do it
- Weigh the empty cup with its string and record its mass.
- Clamp the top 3 cm of a strip so 17 cm hangs over the edge, and hang the empty cup from a hole punched 1 cm from the bottom.
- Add 20 g at a time, waiting 5 seconds between loads. Record the load at which the strip breaks or tears at the hole, as the cup's mass plus the masses in it; stop when the total load reaches 1 kg and record 'held 1 kg' if it has not broken.
- Before it breaks, measure how much the strip has stretched (plastic stretches visibly; paper does not).
- Repeat three strips of each material and take the mean breaking load (strips that held 1 kg are reported as 'more than 1 kg').
- Graph breaking load for the five materials.
- Explain why a shopping bag is plastic, a page is paper and a tent is fabric using the results.
What you should see
Breaking loads in grams are the learner's data, and some strips may reach the 1 kg limit. Most strips fail at the punched hole, because the hole narrows the strip and concentrates the force around it. The plastic bag strip stretches visibly before it fails; the paper, baking paper and foil strips stretch very little, and foil tears easily once a nick starts at the hole. The finding is the class's ranking by breaking load together with how much each material stretched, which is what decides its use.
What changes
- What you change
- material
- What you measure
- load at which the strip breaks
- What you keep the same
- strip width and length
- hole position
- rate of loading
Common misconceptions
Each of these ideas is wrong, and the activity is a chance to test it.
- Thin things are always weak.
- Stretchy means weak.
- Metal is always the strongest material (a thin foil strip tears easily at a nick).
Safety card
Hazards
- falling masses
Controls
- tray beneath
- feet clear of the drop
- load capped at 1 kg
Note
Risk assessment before the lesson using Primary RiskAssess or the school's own template.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
Sources
The pages the author read to write this activity.
- www.scootle.edu.au/ec/search?accContentId=AC9S4U04
- curriculum.nsw.edu.au/learning-areas/science/science-and-technology-k-6-2024/outcomes
- www.nsw.gov.au/education-and-training/nesa/curriculum/science/science-and-technology-k-6-2017
- primaryconnections.org.au/v84-sequences/material-world
- primaryconnections.org.au/teaching-sequences/year-4/packaging-pioneers