Techniquest @ Home
Why should your Techniquest experience end when you leave? The answer is – it shouldn’t! That’s why we have created some science experience for you to try at home. Each month, a new experiment will be added. Don’t forget to visit the webpage each month for the latest trick to have a go at.
Make your own Slime
You will need:
- A large bowl of corn flour
- Water
- Food colouring (optional)
How you do it
- Keep some corn flour aside. Then, in the bowl, slowly mix water into the rest of the corn flour until you make a mixture with a runny consistency.
- If you’ve added too much water then use the corn flour you’ve kept aside to make it more ‘slimy’.
Investigate
Try stirring it slowly and then quickly. Then try hitting it hard with your fist and then in slow motion.
Scoop out a handful of mixture and roll it with both hands quickly to make a ball. What happens if you stop rolling and let the ball sit in your palm?
When you’ve finished, your slime can be washed down the sink and any splashes brushed away when dried.
What it shows
Cornflour slime is a dilatant fluid which means that its viscosity (runniness) changes when it is under different pressures (called shear forces).
Without any pressure the slime is runny. By stirring it quickly you are applying a force, causing the slime to become thicker. As soon you stop the slime becomes runny again. Rolling the slime has the same effect.
Corn flour particles have a rough surface. When a fast shear force is applied to the slime (by hitting it)
the cornflour
particles lock together and the slime feels like a solid. When a slow shear force is applied the particles have time to roll over each other. The water flows between the particles and the slime looks like a liquid.
Most fluids are called ‘Newtonian’ because their viscosity does not change when a ‘shear force’ is applied.
Super Straw
You will need:
- Plastic straw
- Large potato
How you do it
Ask the group if they believe you can push a straw through a potato. Take opinions and any methods offered.- You may wish to make this a bit of a magic trick with lots of checking of the straw and potato etc.
- To do the ‘trick’ keep your thumb firmly over the top end of the straw as you quickly plunge the bottom end into the potato.
What it shows
This experiment demonstrates Pneumatics and Physics. The increased air pressure in the straw stops it from crumpling as you force it through the potato. The force is concentrated on the small surface area of the edge of the straw so it is able to cut through the potato.
How to Make Super Bubbles
You will need:
- Washing up liquid
- Wire coat hanger
- Glycerol (also called glycerin)
- Water Help from an adult
How you do it
- Add 3 parts washing up liquid to 7 parts warm water then add 1 part glycerol.
- Mix it really, really well and let it cool.
- Take a spare wire coat hanger and bend it into a big circle with the hook as a handle.
- Pour some of your bubble mix into a flat dish, bigger than your blower, dip the blower in and wave it through the air.
What it shows
How can you make big bubbles that last a long time? You need to know a little about bubble science. Bubbles are made up of two layers of soap with water in between. When this water evaporates the bubble bursts, because it is too dry to keep its shape.
Knowing this already gives us some clues about bubbles. To stop the evaporation it’s best to make bubbles when it’s cold and damp. But the secret to making really big bubbles that last is using some stuff called glycerol. This syrupy stuff can be bought in pharmacists and supermarkets. You might even have some at home already; some people drink it when they have a sore throat, and it’s also used to make icing. Glycerol gives bubbles strength and stops them from drying out too quickly.
Investigate
Experiment with your mixture and your blower; try using more washing up liquid or more glycerol. Try making some other bubble blowers, or bending your coat hanger blower into new shapes – can you blow a square bubble? Have fun.
Alka-Seltzer Rocket
You will need:
- An empty film canister
- An Alka-Seltzer tablet (or other soluble vitamin or aspirin tablet)
- A small tray to contain any spilt water
- Small jug of water
How you do it
- Place around a 1/3 of the Alka-Seltzer tablet in the film canister.
- Cover the piece of tablet with about 1cm of water. Put the lid on quickly and make sure the seal is very tight (if the lid doesn’t fit tightly all you will get is a disappointing fizz as the gasses escape through the seal.)
- Give the canister a little shake then tip it upside down on the tray. Make sure you and the audience are well back.
- After a few seconds the bottom of the film canister should rocket up into the air.
What it shows
The Alka-Seltzer tablet produces carbon dioxide bubbles when added to water. The gas gets trapped inside the container and as more gas is produced, the pressure rises until there is enough force to overcome the seal of the lid. The built- up pressure exerts enough force to shoot the canister into the air.
Clucking cup
You will need:
- Fishing line or string
- Plastic cup
- Damp cloth
How you do it
- Make a small hole in the base of the cup and thread the string through it.
- Tie a knot in the end of the string so that it cannot be pulled out. Pull the damp cloth along the length of string
What it shows
The string starts vibrating as the cloth sticks and slips along it. This is just like the movement of a violin bow across the strings. By passing a damp cloth along a piece of string alone, a noise would be produced, but it would be very quiet. The cup acts like a speaker, allowing a larger surface area to vibrate, making more air vibrate, resulting in the sound being amplified or made louder.
Möbius Strip
You will need:
- A piece of A4 paper
- A pair of scissors
- Sticky tape
How you do it
- Cut the A4 paper lengthways into four or five equally sized strips.
- Take one of your strips and hand out the others to members of your audience, asking them to copy what you do.
- Give your strip of paper a half-twist and then join the ends together to form a loop. This shape now only has one surface!
- Don’t believe me? Then take a pencil and draw a line down the middle of the loop without taking the pencil off the paper - what happens? The line goes right around the loop inside and out, so it must have only one surface!
- Now cut along the line with a pair of scissors. Let’s take a vote from your audience to see whether they think you will end up with two separate loops or one large one. You should end up with one large loop.
- Ask the audience what they think will happen if you cut this big loop again. This time you should end up with two loops linked through each other
What it shows
Topology is the mathematical study of shapes. The Möbius strip or Möbius band was formally discovered in 1858 by the German mathematicians August Ferdinand Möbius and Johann Benedict Listing, though it had been observed previously in art and manuscripts.
Paper Clip Trick
You will need:
- A strip of paper
- Two paperclips
How you do it
- Fold the paper over and then back, so you get a Z-shape (A).
- Now slide on the paper clips, so that the paper is held in this shape. Each paper clip needs to go inside an angle of the Z (B).
- Now ask the group what will happen when you pull both ends of the paper. Take answers and then do the demo. When you pull on each end of the paper (C), the paper clips will fly up into the air and land joined together (D).
- You will need to repeat this so that everyone can see what happens. As an extension, ask them to try to judge how far away the paper clips will land.
What it shows
Topology is the mathematical study of shapes. The two paper clips are never truly linked. A paper clip can be straightened to a plain piece of wire and you can never link two straight pieces of wire. To be truly linked they would have to be two circles, like links in a chain. All that the pa- per does is wrap the two pieces of wire around each other.
Surprising Gravity
You will need:
- A4 paper
- Phone directory or heavy book
How you do it
- Ask your audience, “If you drop the plain paper and the phone book from the same height at the same time, which will hit the ground first?” Hopefully someone will say the book.
- Why do they think this is?
- Tell them that the paper and book will land at the same time; then scrunch up the piece of paper and drop both objects at the same time. They should both land at the same time.
What it shows
Gravity pulls objects down to Earth with the same force; heavier items do not drop faster as you would expect. The reason a flat piece of paper falls more slowly is because of the action of air resistance or drag. When you scrunch up the paper you are making it more aerodynamic, which reduces the effects of air resistance.
 |
 |
Balloon Kebab
You will need:
- Balloon
- Wooden kebab stick
- A steady hand
How you do it
- Inflate the balloon (leaving a little stretch).
- Carefully push the point of the kebab stick into the top of the balloon (usually noticeable due to stronger colour).
- A twisting motion as you push usually helps.
- Once the kebab stick is in, you simply push it through the thick bit on the knot side, and hey presto, a balloon kebab!
What it shows
There is still elasticity in the latex and this allows the formation of a seal as you passthe stick through the balloon. Where th
e balloon is stretched tightly, it is not able to form a seal as there is too little latex, and once broken it will tear out of control bursting the balloon.
