What it shows
Glues stick by filling the tiny gaps in the surfaces and hardening, and starch paste from the kitchen works for paper. You compare the strength of flour paste, rice paste and school glue by hanging load from glued strips.
The science
Glue is a sticky liquid whose molecules cling to the surface of both strips and then harden to link them. Starch paste is made by heating starch with water so it swells into a gel. Stronger glues like school glue have long polymer molecules that grip better, and a thin, even layer sticks best.
Materials
Cost: under Rs 50. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- Flour (maida) and cooked rice
- School glue stick or liquid glue
- Water and a small pan (adult only)
- Strips of card or paper, 2 cm wide
- A small bag or cup to hang weights
- Coins or marbles as weights
- A ruler and notebook
Safety
For this project: An adult must cook the paste, because hot starch burns. Keep glue away from mouth and eyes and wash hands afterward.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
7 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Ask an adult to boil one spoon of flour in a cup of water, stirring till it thickens, and let it cool.
Mash cooked rice with a little water to a smooth paste.
Cut 12 equal strips of card and glue pairs together with an overlap of 3 cm, four pairs for each glue.
Press each pair under a book for thirty minutes.
Let all of them dry for 24 hours.
Hang each strip from a clip and add coins in a bag until the join breaks.
Record the load for each and calculate the average for each glue.
What you should see
School glue holds the heaviest load, flour paste is next and rice paste is weakest. The averages show clear differences, with starch pastes strong enough only for paper.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What is glue made of?
Polymer or starch molecules that stick to surfaces.
2Why does a thin layer work best?
The surfaces stay close and the glue does not stay soft in a thick lump.
3Why wait 24 hours?
The water has to dry for the glue to harden.
4How was the test made fair?
Equal strips and equal overlap area.
Take it further
Test how the joint area changes the holding load by changing the overlap from 1 cm to 5 cm.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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