Flying Cup Glider

Create a fantastic flying machine in seconds and marvel at its erratic flight!

Materials

  • Two cups (paper, plastic or foam)
  • Tape
  • Rubber bands

Safety first!

  • Before launching your flying cup glider, make sure you have plenty of space around and in front of you – it’s usually safest to do all your launches outside.
  • Wear safety glasses or other eye protection when launching your glider.

Instructions

  1. Tape the two cups together at the base.

2. Make a chain of rubber bands. Start with two rubber bands overlapping each other, then loop one of them back through itself to join and pull to secure. Repeat until you have a chain long enough to comfortably wrap around the middle of your cup glider (around 15-20cm).

3. Find a safe launching area. Hold the cups in one hand, and use your thumb to hold one end of the rubber band chain against the join in the cups. With your other hand, wind the rubber bands firmly around the cups once, stretching them a little as you go. Hold the other end of the rubber band chain. You’re ready to launch!

4. Hold the cups horizontally in front of you, with the hand holding the rubber band chain slightly forward. Make sure the rubber band chain is coming out from underneath the cups, not over the top. Pull the cups back and angle your other hand up, as though firing a slingshot. Then let go of the cups at the same time as you pull the rubber band chain forwards. The chain should unwind from around the cups, spinning them in the process, which will make your amazing flying machine go!

Further investigation...

  • It might take a few tries to get the hang of launching your glider. Flicking your front hand forwards as you launch can make the cups spin faster and improve your glider’s air time.
  • Try making gliders from different types of cups and see which ones stay in the air the longest. You could also try cutting the cups into different sizes or shapes, or making a paper ‘lid’ for one or both cups to see how these changes affect its flight.
  • Experiment with different lengths of rubber band chain. Does wrapping the band around more times before launching make a difference to how well it flies?

What's happening?

There are four forces acting on any flying or gliding object as it moves through the air:

  • Lift pushes the glider upwards
  • Weight (gravity) pulls the glider towards the ground
  • Thrust pushes the glider forwards
  • Drag (air resistance) is caused by air pushing back on the glider in the opposite direction to thrust.

When you launch a glider, you create thrust as you push the glider forward and release it.

Eventually, weight overcomes lift, and the plane falls to the ground. When drag overcomes thrust, the glider stops moving forwards.

The movement of the air around the glider is also important. Although we can’t feel it, air is always pressing on us from all directions. The amount of force the air exerts on an object is known as air pressure. Air will also tend to move from areas of higher pressure to areas of lower pressure.

A scientist called Daniel Bernoulli discovered that the speed air is moving also affects the pressure – faster-moving air has lower pressure than slower moving air. This is known as Bernoulli’s principle and understanding it is very important in understanding how objects fly.

With our spinning cup glider, the fast moving air around the glider causes a difference in the air pressure above and below the glider. The air below the glider has a higher pressure than the air above it, and because air tends to move from higher to lower pressure, the air below the glider pushes it up, creating lift.

There’s also another phenomenon involved here. A spinning object moving through the air will tend to curve towards the direction it is spinning. You can see this in action in many sports – when a tennis ball is hit or a soccer ball is kicked in a way that makes it spin, it will curve or ‘bend’ in the air. This is called the Magnus effect.

Check your understanding

  1. What are the four forces that affect a flying or gliding object?
  2. Draw a diagram of your glider and use arrows to show the direction of each force.
  3. Where does your glider’s thrust come from?
  4. Why does the glider eventually fall to the ground?
  5. Explain your understanding of the following scientific terms: air pressure, Bernoulli’s principle, Magnus effect

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Myth-busting Monday: Bacon vs Cigarettes

Mondays are great for busting myths.

(They’re also great for going meat-free, which may seem even more appealing after reading this article.)

Today’s myth concerns the cancer-causing nature of processed meats, and how it compares to other well-known carcinogens.

Myth: Eating bacon is as bad for you as smoking cigarettes.

Truth: It is true that in October 2015, the World Health Organisation (WHO) released a report that confirmed a link between processed meats and cancer. Not only that, it placed processed meats such as bacon, frankfurts and salami in the Group 1 Carcinogens category, alongside cigarettes, asbestos, and radioactive metals.

This prompted a flood of articles with headlines along the lines of today’s myth – that eating processed meats was as bad for you as smoking cigarettes.

BUT…all carcinogens are not created equal. There is equally strong evidence that all Group 1 substances are carcinogenic, but that doesn’t mean they are all equally carcinogenic.

Confused? Maybe some stats will help.

The overall lifetime risk of getting bowel or colorectal cancer is about 6% – in other words, about 6% of the population will have one of these cancers at some time in their lives.

The WHO report found that each daily 50g portion of processed meat you eat increases your overall risk of these cancers by 18%. That is, if you eat 50 grams of bacon, ham, or salami every day, your risk increases to 7.08% (6 x 1.18). If you eat 100 grams of bacon every day, it increases to 8.35% (6 x 1.18 x 1.18), and so on.

These figures are for consistent daily consumption over your whole life – so the effect of an occasional BLT or hot dog on your cancer risk is minimal.

Smoking cigarettes, on the other hand, increases your overall cancer risk by a much higher percentage. The Cancer Council states that smoking 10 cigarettes a day DOUBLES your cancer risk, and smoking more than 25 a day doubles your risk again – that is, an increase of 400% on the overall risk (which is also around 5-6%).

Smoking is also implicated in 86% of lung cancer cases and 19% of all cancer cases – by comparison, daily consumption of processed meats is linked with 21% of bowel cancers and 3% of all cancers.

These numbers are certainly significant and should probably make bacon-lovers reconsider their consumption…but smoking is still far worse for your health overall.

Learn more

If you’d like to learn more about the specifics of the World Health Organisation report, visit their Q & A page on this topic.

For Australian-based advice on how to reduce your cancer risk by swapping to healthier alternatives in various areas, visit the Cancer Council website.

To read more about the cancer-linked ingredients in bacon, have a look at this article from The Guardian.

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Sherbet

Materials you will need for Sherbet

Whip up this fabulously fizzy sherbet in seconds using pantry ingredients.

Materials

  • Icing sugar
  • Jelly crystals
  • Bicarbonate of soda (bicarb)
  • Citric acid
  • Small bowl or container with lid
  • Measuring spoons (tablespoon and teaspoon)
Materials you will need for Sherbet

Safety first!

  • Always wash your hands before and after preparing food (yes, this is a science experiment, but you do get to eat it too!).
  • If you have any food allergies, intolerances or aversions, make sure to check that all products you use are safe for you to eat.
  • Citric acid and bicarb may cause mild irritation if you get them in your eyes. Take care not to rub your eyes while making your sherbet.

Instructions

    1. Mix together the sherbet ingredients using the following measurements:
      • 1 tablespoon icing sugar
      • 1 teaspoon jelly crystals
      • 1/2 teaspoon citric acid
      • 1/4 teaspoon bicarbonate of soda

    A little bit of sherbet goes a long way, but if you’d like to make a bigger batch, just double the quantities given.

    1. Stir thoroughly, breaking up any clumps. If your container has a tight lid, put it on and shake the container to mix it.
    2. Taste your sherbet and adjust the ingredients to taste. You should only add tiny amounts when adjusting, and mix thoroughly before tasting again.
      • Citric acid is very sour – it’s what gives lemons and other citrus fruits their sour taste. If your sherbet is too sour, add a tiny bit more bicarb.
      • Bicarb on its own tastes soapy and bitter, so if this taste is overpowering, add more citric acid.
      • Icing sugar is just very finely ground sugar. If your sherbet isn’t sweet enough, add a bit more.
      • Jelly crystals are a combination of sugar, gelatine, flavouring, and colouring. Add a bit more to give your sherbet a flavour boost.

What's happening?

Sherbet gets its delightful fizz from the combination of citric acid and bicarbonate of soda, otherwise known as bicarb. Citric acid, as its name suggests, is an acid, while bicarb belongs to another group of chemicals known as bases.

When we mix an acid and a base together, we get a chemical reaction. In a chemical reaction, the molecules of the starting chemicals (known as reactants) break apart and reform into new chemicals (known as products). In this case, the new chemicals formed are water, sodium citrate (a type of salt), and carbon dioxide gas, which escapes as tiny bubbles. We can’t see all this going on, but the bubbles of gas give us a clue that a chemical reaction has taken place.

But our sherbet didn’t fizz as soon as we added the two dry chemicals together. In powder (solid) form, the chemicals can’t mix together as easily as when they are dissolved. When you add water, or put the sherbet in your mouth with your saliva, the citric acid and bicarb molecules can find each other more easily and react.

A chemical that helps a reaction happen, but isn’t itself changed by the reaction, is called a catalyst – in this case, water is a catalyst that helps the reaction between citric acid and bicarb to happen.

The other two ingredients in our sherbet – icing sugar and jelly crystals – are just there to make it taste yummy. They aren’t needed for the chemical reaction, but sherbet made from just citric acid and bicarb wouldn’t taste very nice.

Check your understanding

  1. Which two ingredients in the sherbet are involved in the chemical reaction?
  2. Which ingredients are not involved?
  3. Can you think of any other chemical reactions that might happen in the kitchen?
  4. Measure how many teaspoons of icing sugar it takes to fill up a tablespoon. A teaspoon is 5 millilitres (ml) – how many ml are in a tablespoon?
  5. How many teaspoons of sherbet does this recipe make?
  6. Calculate how much of each ingredient you would need if you used a metric cup (250ml) of icing sugar.
  7. Explain your understanding of the following scientific terms: chemical, chemical reaction, molecule, reactant, product, catalyst.

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Myth-busting Monday: Pouncing Pepper

You might have seen this viral (ahem) video doing the rounds – a preschool teacher is using the ‘pouncing pepper’ demonstration to show her students how soaps keep germs away.

Myth: The ‘pouncing pepper’ demonstration shows how soap repels germs from our hands.

Truth: Of course, anything that gets people washing their hands more often is definitely a winner (whether or not there’s a global pandemic). And pouncing pepper is a great demonstration of a scientific phenomenon, but perhaps not the one you might think…

You can do this demonstration at home using just a few materials. A cotton tip or finger is dipped into some water with pepper sprinkled on top, and gets covered with pepper. But when the finger-dip is repeated with detergent, the pepper instantly jumps away!

So does soap repel germs in the same way it appears to repel the pepper in this demonstration? No. In truth, pouncing pepper doesn’t actually demonstrate the effectiveness of soap in removing germs.

This experiment works because of water’s surface tension. Water likes to stick to itself, and surface tension is a bit like a skin formed by the water molecules at the surface. The pepper is small and light enough that the surface tension can support it. But something bigger or heavier, like a person, can break through. You’ll know all about this if you’ve ever bellyflopped into a pool!

So how does soap affect all this?

Soaps and detergents reduce the surface tension of water – this is part of what helps them clean away oils from our hands and dishes. But the germs don’t exactly leap away.

Bacteria and viruses are partially made up of fats, which are broken down by detergents – the detergent reduces the water’s surface tension, allowing it to get between the bits of oil. Detergent is also a long molecule with one end that attracts water, and the other attracts oils. This allows the oil to mix with the water, and be washed away as you rinse.

So back to our pepper experiment. When you touch the detergent to the surface, the surface tension is reduced in that one spot. It’s a similar effect to popping a balloon – if the tension is reduced in one spot, the higher tension everywhere else pulls back from that spot, making the ‘hole’ bigger. And the pepper just helps us to see how those water molecules at the surface are moving.

So this awesome experiment is a great demonstration of how soap changes the surface tension of water, but unfortunately, germs don’t leap away from soap like the pepper does. Which means you need to keep washing your hands! Properly! Go and do it now!

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Pouncing Pepper

Watch how detergent changes the surface tension of water in this amazing demonstration!

Materials

  • White plate
  • Finely ground pepper
  • Detergent or liquid soap
  • Water
  • Cotton tip (or finger)

Instructions

  1. Pour some water into the plate, then gently add a light sprinkling of pepper.

2. Touch your cotton tip (or finger) onto the surface of the peppery water. Observe what happens.

3. Put a small amount of detergent or liquid soap onto your cotton tip, then touch it to the surface of the water again. Observe what happens.

Further investigation...

  • What happens if you touch the surface of the water with the detergent a second time?
  • Repeat the experiment (clean the plate in between) with different types of soaps or detergents. What differences do you observe in the results?
  • Clean and refill the plate with water. What other small, light objects can you find that can be supported by the water’s surface tension?

What's happening?

This experiment works because of water’s surface tension. Water likes to stick to itself, and surface tension is a bit like a skin formed by the water molecules at the surface. The pepper is small and light enough that the surface tension can support it. You can feel the resistance of surface tension if you slap your hand onto the water in a bucket or bath – or belly-flop into a pool!

Soaps and detergents are both examples of surfactants, which are chemicals that reduce the surface tension of water. This is part of what helps them clean away oils and dirt from our hands and dishes.

When we touch the surface of our pepper water with the detergent, it reduces the surface tension in that one spot. This means that the surface tension is higher everywhere else, so the rest of the molecules at the surface pull back from that spot, stretching the ‘hole’ until the whole surface is affected. It’s a similar effect to popping a balloon. This movement between areas with different surface tensions is called the Marangoni effect.

The pepper in this demonstration helps us to see how those water molecules at the surface are moving. After the pepper has ‘pounced’, the lower surface tension let some of those bits of pepper sink to the bottom.

You may have noticed that you can only make the pepper ‘pounce’ once. If you want to repeat the experiment, you’ll need to rinse all the detergent off the plate and refill it with clean water.

Check your understanding

  1. What happened when you touched the surface of the water without the detergent?
  2. What happened when you touched the surface of the water with the detergent?
  3. Could you make the pepper ‘pounce’ more than once? Why/why not?
  4. Explain your understanding of these scientific terms: surface tension, molecule, surfactant

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Mexican Jumping Bean

A colourful family of Mexican jumping beans made from Easter egg wrappers

Put those old Easter egg wrappers to good use in this fun activity.

Materials

  • Easter egg wrappers or aluminium foil
  • Marbles
  • Plastic container with lid
  • Cylindrical object with diameter slightly bigger than the marble’s (e.g. whiteboard marker)
Materials you will need for Mexican Jumping Bean

Instructions

  1. If you’re using foil, cut or tear it into pieces approximately 8cm x 6cm. Use a ruler to help you tear it straight. If you’re using Easter egg wrappers, smooth them out.
  2. Starting at the short edge, roll the foil around the marker, leaving about 1.5-2cm hanging over the end of the marker.

3. Firmly press the overhanging ends of foil around the end of the marker to close one end of the foil tube.

4. Slide your foil tube off your marker and drop a marble inside.

5. Carefully pinch and fold over the other end of the tube to enclose the marble, taking care not to squash the tube (the marble should have space to move around inside). Don’t worry if it’s not very neat – we’ll fix that in the next step.

6. Place the foil package inside the container, put the lid on, and shake it until the ends are rounded and smooth.

7. Roll your completed jumping bean around to see how it moves!

Further investigation…

  • Try different sizes of foil and marbles to make more beans, and observe how they move differently.
  • How does the bean’s movement change if you use several smaller balls in place of the marble?
  • Try rolling the bean down a sloping surface, such as a piece of heavy cardboard. The foil is smooth and a bit slippery – how could you make it grip the surface better?
  • Can you design a similar rolling toy made from paper or cardboard?

What's happening?

When you shake the jumping bean around in the container, the foil gets squashed between the marble and the sides of the container. This creates the bean’s smooth, rounded ends.

As the bean rolls along, the marble and the foil move separately from each other. Although it may look like it’s not moving, the marble is secretly rolling along inside the foil. The marble keeps rolling until it hits the end of the foil tube. The foil tube flips over, and the marble continues rolling until it hits the other end.

This fun experiment gets its name from an actual Mexican plant (Sebastiana pavoniana) which has a very special relationship with a species of moth (Cydia deshaisiana). The moth lays its eggs inside the seed pod of the plant, and when the larvae hatch, each one burrows inside its own seed, eats out the middle, and lives in there for several months. When the seed gets warm (e.g. by someone holding it in their hand), the larva moves around, making the seed jump in a very similar way to these foil ones!

Check your understanding

  1. Describe the push and pull forces that make the jumping bean move.
  2. On what type of surface did the jumping bean move best?
  3. How did the Mexican Jumping Bean get its name?

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Skittle Rainbow

This colourful experiment uses Skittles to demonstrate solubility and diffusion. 

Materials

  • A packet of Skittles lollies
  • A flat plate with a rim (white if possible)
  • Tap water in a small cup or jug
  • A sugar cube or 1 teaspoon plain white sugar
Materials you will need for Skittle Rainbow: Water, skittles, white plate, sugar cubes

Instructions

  1. Make a pattern of Skittles around the edge of the plate. Try not to let them touch, and space them as evenly as possible.

2. Gently pour your water into the middle of the plate until all the Skittles are in the water, being careful not to disturb or move the Skittles.

3. Watch what happens! (For best results, be careful not to bump the plate or the table.)

4. When the colours have reached the middle, carefully place a sugar cube (or a small pile of plain sugar) into the middle of the plate. What happens to the colours now?

What's happening?

Skittles are tasty little balls of sugar with a coloured sugar coating. When the water touches the Skittle, the sugar in the coating starts to dissolve, taking the colour with it.

When something dissolves, it might look like it’s disappearing, but what’s really happening is that the molecules are separating from each other and floating around in the water – the sugar is still there, even though we can’t see it.

Stirring helps all the sugar dissolve and spread quickly and evenly through the liquid – this is why you might stir a cup of tea or coffee after adding sugar.

But even if we don’t stir, the molecules of sugar spread themselves out evenly anyway. This is a process called diffusion.

In diffusion, dissolved molecules move from an area where there are lots of them, to areas where there aren’t as many, until they’re evenly spread.

When the sugary coatings of the Skittles first started to dissolve, all the sugar was around the edges of the plate. The colours dissolved along with the sugar, which let us see where the sugar molecules were going – they moved in towards the centre of the plate where there was no sugar.

When you add the sugar cube in the middle of the plate, once again the sugar starts to dissolve. But suddenly, there’s a lot more sugar in the middle of the plate than there is around the edges. So we can see that extra-sugary water in the middle starts to push back out towards the edges to even things up.

Check your understanding

  1. What happens to something like sugar when it dissolves? Does it disappear?
  2. Is dissolving an example of a physical change or a chemical change? Explain your answer.
  3. Why did we see the colours moving towards the middle of the plate?
  4. Why didn’t the colours mix together in the middle of the plate?
  5. Describe what happened when you added the sugar cube. Why did the water in the middle of the plate turn clear?
  6. Explain your understanding of these scientific terms: dissolve, diffusion, molecule

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Coat Hanger Gong

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Materials

  • Wire coat hanger
  • Two pieces of string about 40-50cm long

Instructions

  1. Tie the pieces of string to the two bottom corners of the coat hanger.

2. Wrap the other ends of the strings around your pointer fingers and put your fingers in your ears.

3. Gently swing the coat hanger so that it hits something solid (for example, a table) and listen to the sound it makes.

Further investigation

  • Try swinging the coat hanger into different things. Does a table sound the same as a couch?
  • Ask a friend to tap the coat hanger with objects made from different materials. Does it sound the same when a finger and a spoon taps the coat hanger? 
  • Repeat this experiment using something else instead of the coat hanger. Try a metal spoon. Does it work as well with a plastic coat hanger?

What's happening?

When you tap the coat hanger onto a table normally (without fingers in your ears), the coat hanger vibrates and makes the particles in the air next to the coat hanger vibrate. The vibration is passed from one air particle to the next to the next to the next. This is a called a sound wave. If this sound wave moves into your ear and starts vibrating your ear drum, you can hear sound. 

But the particles inside the coat hanger start to vibrate as well. And this vibration is passed from one coat hanger particle to the next to the next to the next. Then the vibration passes into the string and the string particles vibrate. The vibrations travel up the string and directly into your ear.

It sounds louder because sound can travel more easily through a solid than through the air. The particles in a solid are much closer together compared to the particles in the air.

This is why it will sound louder to someone that is directly connected by the solid string to the coat hanger, than someone who hears the sound through the air.

You can also experience this with a cup and string phone. Tie a string to the bottom of two paper or plastic cups. One person speaks into one cup while the other listens through the other cup.

Check your understanding

  1. Describe the sounds the coat hanger made, both before and after you put your fingers in your ears. How were the sounds different?
  2. How does sound reach our ears?
  3. Why does putting your fingers in your ears in this experiment make the coat hanger sound louder?
  4. What makes the loudest sound? Which sound do you like the best?
  5. Explain your understanding of these scientific terms: vibration, sound wave

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Hoop Glider

Picture of a hand holding a completed Hoop Glider

You won’t believe how simple this glider is to make – or how well it flies!

Materials

  • Light card or thick paper
  • Ruler
  • Straw
  • Tape
  • Scissors
  • Pencil
Materials you will need for Hoop Glider

Safety First

  • Before you throw your glider, make sure you have plenty of space around you and the glider’s path is clear (remember, it may not fly completely straight!). We recommend conducting all test flights outside, but if this isn’t possible, a straight hallway would also work. 

Instructions

  1. Cut two strips of card about 1.5cm wide, one from the long edge of the card (about 30cm long) and the other from the short edge (about 19cm long).

2. Use tape to make your strips of card into hoops. (Tip: use the smallest amount of tape possible so it doesn’t add too much weight to your glider.)

3. Tape one hoop to each end of the straw, making sure they are lined up.

4. To throw your glider, hold it with the hoops pointing up, and the small hoop at the front.

Further investigation

  • Experiment with different types of throws. What happens if you throw your glider upside-down or back to front?
  • Try making more gliders with different sized hoops or different lengths of straw. Which ones fly the furthest? Which designs don’t work very well?
  • You could even add more hoops to the same glider – how does this affect how well it flies?

What's happening?

There are four forces acting on a glider as it glides through the air:

  • Lift pushes the glider upwards
  • Weight (gravity) pulls the glider towards the ground
  • Thrust pushes the glider forwards
  • Drag (air resistance) is caused by air pushing back on the glider in the opposite direction to thrust.

These forces need to be balanced for the glider to stay in the air.

When you throw the glider, you create thrust as you push the glider forward and release it. The circular shape of the wings on the glider creates lift.

Eventually, weight overcomes lift, and the plane falls to the ground. When drag overcomes thrust, the plane stops moving forwards. To help the glider stay in the air longer, consider how you might achieve the following:

  • Increase lift – the curved shape of the wings helps create lift. Does a bigger or wider wing create more lift?
  • Reduce weight – could you use fewer or lighter materials to make the glider?
  • Increase thrust – the thrust for an aeroplane is provided by an engine, but for your glider it’s all up to you and your throwing action. How could you provide more forward force for your glider?
  • Reduce drag – flying machines and animals are usually fairly pointy at the front, so they can slice through the air more effectively. (You can test this yourself – try holding a sheet of paper vertically and dropping it, then hold it flat like a tabletop and drop it again. Which one reached the ground more quickly?) How can you improve the shape of your glider to reduce the amount of air hitting it front-on?

Sometimes, making one change can affect more than one of these forces. For example, a larger hoop-shaped wing might create more lift, but it will also be heavier and weigh your glider down. 

Check your understanding

  1. What are the four forces that affect a flying or gliding object?
  2. Draw a diagram of your glider and use arrows to show the direction of each force.
  3. Where does your glider’s thrust come from?
  4. Describe how changing the shape, size, or orientation of the glider’s wings affected its flight.
  5. Describe how changing the length of the glider’s body (straw) affected its flight.
  6. Which of your gliders worked the best? Why?

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Popstick Harmonica

Two completed Popstick Harmonicas

Make a fun musical instrument using a few simple materials. 

Materials

  • 2 popsticks (large ones work best)
  • 2 small rubber bands
  • 1 straw
  • 1 wide rubber band
  • Scissors
Materials for making popstick harmonica

Instructions

  1. Cut two pieces of straw about 4cm long each.

2. Stretch the wide rubber band over one of the popsticks.

3. Slip one piece of straw under the rubber band, a few centimetres from one end.

4. Place the other popstick on top and wrap one of the small rubber bands around the end where the straw is. The rubber band must be outside the straw.

5. Place the other piece of straw between the two popsticks a few centimetres from the other end, but this time on top of the wide rubber band. Secure with a small rubber band.

6. To play your harmonica, put the popsticks in your mouth (between the straws) and blow. The large rubber band vibrates between the popsticks to create the sound. (You might need to squeeze the popsticks together a little bit.)

What's happening?

When you blow through the harmonica, the rubber band vibrates and you hear a sound.

When the straws are closer together a smaller length of the rubber band is vibrating. This makes the rubber band vibrate faster, and you hear a higher pitch.

When the straws are further apart, more of the rubber band can vibrate. This slower vibration allows us to hear a lower pitch.

How fast or slow something is vibrating is called the frequency.

Check your understanding

  1. Which part of the harmonica is vibrating to make the sound?
  2. How does moving the straws change the sound of the harmonica? How would you describe the sound?
  3. Explain your understanding of these scientific terms: vibration, pitch, frequency

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