Boom! 50 Fantastic Science Experiments to Try at Home with Your Kids (PB) E-Book

Chris Smith

• Herausgeber: IMM Lifestyle Books
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch
• Veröffentlichungsjahr: 2019

Seitenzahl: 181

Beschreibung

This amazing book from the famous Naked Scientists offers a fun way to introduce science to kids, with 50 simple experiments that produce spectacular results. Want to know how to create fireworks from a bag of chips? Turn rice into quicksand? Generate a cloud in a soda bottle? How about build a toaster-powered hot air balloon, or work out the speed of light using margarine and a microwave? The results will amuse, astound, and educate in equal measure, whether you're 8 or 80. Most of these activities can be performed with commonplace materials that are probably lying around the house. Concise scientific explanations are included on how and why the experiments actually work. Each activity is straightforward and manageable, yet impressive enough to get anyone interested in science. So whether it's racing jelly jars, making a bowl invisible, or instantly freezing soda before your eyes—with the Naked Scientists' help, you'll never have a dull rainy day again!

Leseprobe

Learn how to extract DNA from a kiwifruit (page 53).

CONTENTS

Make your own submarine

Create a cloud in a bottle

Levitating ping pong balls

Rice quicksand

Homemade litmus test

Iron out your cereal

Hurricane in a bottle

Is that egg hard-boiled?

Measure the speed of light with margarine

Freeze a soft drink, instantly

Chip bag/crisp packet fireworks

Homemade fiber optics

Soft drink volcano

Toaster-powered hot-air balloon

Use your loaf—how to make bread taste sweet

Why is the sky blue?

Extract DNA from a kiwifruit

How to fool your senses

Electric slime

The chemistry of coppers

Make your own water strider/pond skater

Make your own magnifying glass

Homemade lava lamp

Strange glows from sugar

The mysterious sound of an oven shelf

Just chill out… your glow-stick

Tangtastic: make your own fizzy candy

Plant hydraulics, and why slugs and salt don’t mix

Hang an ice cube from a thread

Liquid behaving badly

Invisibility cloak

Turn milk into cheese

Is that really orange?

Homemade mini fire extinguisher

How to make a force field

Invisible ink

Seeing the invisible

The world’s cheapest camera

Images from a magnifying glass

Confuse your balance

DIY Butter

Boiling yogurt containers

Flying tubes

Make your own Gulf Stream

Music from a wine glass

The science of tidal waves

The science of pool

The science of bells and coffee cups

Jam jars and flywheels

Waterproof hanky

MAKE YOUR OWN SUBMARINE

In this experiment we’ll find out how submarines sink and resurface and how scuba divers can hover in the water without bashing into the bottom. It’s all about buoyancy and how you can control it.

♦ Take a large (2-quart/2-liter) plastic soft drink bottle and fill it with water.

♦ Add an unopened plastic packet of ketchup or mayonnaise (like the ones given out at fast-food restaurants). The packet will just about float, but if it’s too buoyant try attaching one or more paperclips or modeling clay to the outside so that it sits just at the surface of the water.

♦ Make sure that the bottle is full to the brim.

♦ Now screw on the top very tightly and squeeze the bottle hard.

♦ The sauce submarine will dive to the bottom of the bottle.

WHY does it work?

It’s all down to a piece of physics worked out by the famous Greek “eureka-streaker,” Archimedes. When he leapt out of his bath 2,000 years ago, what Archimedes had effectively discovered was why things float. He found that water pushes up on an object with a force equal to the weight of the water that the object displaces or pushes out of the way. If the displaced water is heavier than the object itself, then it will float upward.

When the ketchup packet is first added to the plastic bottle, it displaces an amount of water that weighs slightly more than it does, and so it bobs around on the surface. When you squeeze the closed bottle, you apply pressure to the water inside. Liquids are incompressible, so the pressure is instead transmitted to the ketchup packet; this contains a small pocket of nitrogen gas (to keep the ketchup fresh).

Unlike liquids, gases can be compressed, so the squeezing effect of the water causes the packet to begin to shrink. This reduces the amount of space it takes up and, hence, the amount of water that it displaces, even though its weight isn’t changing. Eventually, once you squeeze hard enough, the packet will shrink to a point where the amount of water being displaced weighs less than the ketchup packet does, and it will sink.

Why does it surface again when you release the pressure? This is because, as soon as you let go, the gas in the packet re-expands, making the packet less dense than the water around it, so it floats upward.

HOW does this apply to the real world?

Both scuba divers and submarines control their depth using similar principles. Scuba divers wear a BCD (buoyancy control device). This is an inflatable jacket that behaves just like the sauce packet in this experiment, but with the exception that extra air can be pumped into it from the cylinder on the diver’s back. When the BCD inflates, it blows up like a balloon, displacing more water, so that the diver floats upward.

Subs are slightly different. They have ballast tanks around the outside of the vessel. When the submarine dives, some of the air in these tanks is replaced with water, increasing the weight of the vessel. This makes it heavier than the water it’s displacing, so it sinks. To resurface, compressed air stored in tanks inside the submarine is blown into the ballast tanks where it pushes out the water. This makes the vessel weigh less than the displaced water, so it rises again.

SOME OTHER THINGS TO TRY

Try dissolving some salt in the water in your bottle. The more salt you dissolve, the harder it becomes to persuade your ketchup-packet submarine to sink. This is because the dissolved salt increases the weight and, therefore, the density of the water, making the packet more buoyant. This is why ships can carry more cargo at sea than they can in fresh water and why it’s almost impossible to sink in the Dead Sea.

CREATE A CLOUD IN A BOTTLE

Clouds come in all shapes and sizes, but how do they form in the first place? In this experiment we’ll make clouds appear and disappear, with just the squeeze of a bottle.

♦ Take a large (2-quart/2-liter) plastic soft drink bottle and add a small amount of water.

♦ Light a match, blow it out, and drop it into the bottle while it’s still smoking.

♦ Close the bottle tightly.

♦ Squeeze the bottle really hard for about 5–10 seconds, and at the same time give it a swirl.

♦ Stop squeezing and let the bottle expand again.

♦ You should see a cloud appear inside the bottle. Squeeze the bottle again, and it will disappear. Let it go, and it will return.

WHY does it work?

This experiment relies on the physics that powers both a diesel engine and a refrigerator. The sealed bottle is filled with air molecules and a small number of water molecules. When you squeeze the bottle, the energy you use is transferred to the gas molecules inside, causing them to heat up. You can demonstrate this another way by placing your thumb over the end of a bicycle pump as you push down the plunger—you’ll feel your thumb getting hot.

This is exactly how a diesel engine works; the cylinders compress air, heating it up to several hundred degrees Farenheit (Celsius). The diesel is then injected and instantly ignites, releasing the energy it contains.

The bottle contains smoke particles from the match.

Squeezing the bottle raises the temperature, evaporating some of the water.

Let go! Water droplets condense on the smoke particles, forming a cloud.

In our experiment, the extra heat generated by squeezing the bottle encourages some of the water at the bottom of the bottle to evaporate, forming invisible water vapor.

Then, when you allow the bottle to expand again, the reverse effect kicks in. The sudden drop in pressure causes the temperature to fall. Cold air cannot hold as much water vapor as warm air, so the water molecules that evaporated before now begin to link up with each other to form small droplets of liquid water. This is the cloud that appears.

Where does the smoking match come in? It’s very hard for water molecules to condense in clean air. Instead, they look for a surface where they can congregate, and the smoke particles drifting around inside the bottle provide a perfect place for this to happen.

HOW does this apply to the real world?

Most of the clouds you see in the sky form in a similar way. Heat from the Sun evaporates water from the Earth’s surface, and this vapor is carried aloft by rising warm air. As it climbs further from the planet’s surface, the atmospheric pressure drops, causing the air to expand and cool like it did when you released the bottle. Eventually, the air cools to a point where it can no longer hold the water vapor and the water vapor begins to condense.

Just as in our experiment, it does so on particles of dust, pollen, and pollution, that are also in the air. Together, the billions of tiny water droplets form a cloud. When the droplets become large enough, they fall as rain, hail, or snow.

What about fog, is that the same? Sometimes the temperature close to the ground can fall very fast, making water vapor condense at ground level. If there’s no wind to blow it away, the result is mist and fog.

SOME OTHER THINGS TO TRY

Repeat the experiment without the smoke from the match. It’s very difficult to achieve the same effect. Or try breathing on a mirror. You’ll see it gets foggy. This is because the cold surface removes energy from the water vapor in your breath, so it condenses on the glass surface, forming water droplets.

LEVITATING PING PONG BALLS

An antigravity machine would certainly be an asset, and although we can’t claim to have invented one, in this experiment we’ll show you a feat of physics that keeps planes aloft and will also hold a ball suspended in midair.

♦ For this experiment you need a ping pong ball and either a hairdryer or a bendy drinking straw.

♦ Turn on the hairdryer (set to cold if possible).

♦ Point it so it’s blowing a stream of air straight upward. (If you’re using a straw, put the long part in your mouth with the shorter bendy section pointing toward the ceiling and blow hard.)

♦ Hold the ping pong ball in the airstream coming from either the hairdryer or the straw, and then let it go. Mysteriously, it bobs about in the air flow without falling off.

♦ Try angling the airstream, and the ball will follow, even when the flow is tilted over 30 degrees.

WHY does it work?

The air leaving the straw blows the ping pong ball upward, but what keeps it there, and why doesn’t it fly off and fall to the floor? The answer is an effect described in the 1930s by the Romanian airplane designer Henri Coanda. He showed that when air, or a fluid, flows over a curved surface, it can stick to the surface and follow it, so the flow also becomes curved. This means that when the ping pong ball sits in the center of the airstream, the flow traps the ball by passing around it on all sides, sticking to its surface.

Why does it remain in one place? This is thanks to Isaac Newton’s Third Law, that states that for every action there must be an equal and opposite reaction. If the ball tries to move in any direction, the air sticking to its surface will be pulled with it. But if the air is being moved, then there must also be a force pushing back on the ball in the opposite direction, which is what holds it steady. This is why it bobs about in one place, even when the airstream is at an angle.

When the ball sits in the center of the airstream, the forces trying to move the ball to either side balance, so the ball remains steady.

If the ball moves to one side, the air sticking to its surface will be pulled with it, exerting a force in the opposite direction, that pulls the ball back.

HOW does this apply to the real world?

This phenomenon is also the means by which the wing of an airplane generates lift. Air passing below the wing is deflected downward by the curved surface. At the same time, air sticks to the top of the wing due to the Coanda Effect. Because the air is pushed downward by the wing, there is an equal and opposite upward force applied to the plane, keeping it airborne. This is the same principle that held the ball steady in the airstream in this experiment.

However, if the pilot tries to climb too quickly, the airflow can detach from the top surface of the wing, creating an area of swirling turbulence that does not generate any lift. This is called a stall and it can be very dangerous close to the ground because the loss of lift causes the plane to lose altitude very rapidly and, potentially, to crash.

Air passing across the surface of an airplane wing is deflected downward, so the wing is pushed upward, generating lift.

SOME OTHER THINGS TO TRY

You can also demonstrate the Coanda Effect by trickling water from the tap down the back of a tablespoon. Rather than running straight down the back of the spoon, the stream curves around the tip, coming off at an angle.

RICE QUICKSAND

In this experiment, we’ll show you how to pick up a jar of rice without touching it and why this can explain holes in the road…

♦ Take a jam jar and fill it with rice. Basmati rice works best.

♦ Take a knife the same length as the jar and push it all the way into the rice.

♦ Wiggle the knife about, then remove it and reinsert it.

♦ Keep doing this, adding more rice to the jar whenever the level falls.

♦ After several minutes, you will notice that it’s becoming more and more difficult to insert the knife. Eventually, you will be able to lift up the jar just using the knife embedded in the rice.

WHY does it work?

It’s all down to how particles organize themselves, and it’s also the reason why patios and pavements end up uneven, why quicksand is so deadly, and why roads often become full of potholes.

When you first fill the jar, the grains take up random positions with large gaps between them. This makes it very easy to insert the knife because the rice can move out of the way and into the gaps.

As you repeat the process, the rice grains begin to pack together much more tightly and in a more organized fashion. There’s now much less empty space, which is why you needed to top off the jar with rice along the way. If you look at the jar from the side, you’ll see that most of the grains are lined up in rows.

In this compact arrangement, the rice takes up much less space; this increases the density of the rice so that it becomes progressively more difficult for the grains to move out of the way of the blade. Eventually, it’s only possible to insert the knife by breaking, cutting, or distorting the grains, which requires a large amount of force.

The result is that the grains push back on the knife with the same amount of force, creating an effective “rice-vice” that grips the blade firmly with more force than it takes to lift the jar.

HOW does this apply to the real world?

What’s this got to do with patios, pavements, potholes, and quicksand?

When paving stones are first laid down, or when a hole in the road is repaired, the result is usually a flat surface. After a while, vibration from traffic, or people walking over the surface, causes the small particles in the repair or foundation material to compact together.

Just as the level of rice fell in the jar in this experiment, the level of material filling the hole or supporting the paving slab also drops, making a dip in the road or raising a corner of the stone that people can trip over.

And the quicksand? Well, this is a similar principle. Quicksand is composed of a mixture of salt water and sand particles glued together with small amounts of clay. It forms a structure rather like a house of cards, with large water-filled spaces between each of the sand particles.

When you tread on the quicksand, the pressure you apply breaks down the house of cards, and all of the particles pack tightly together around the trapped body part, locking it in place. In fact, the sand is so heavy that the force needed to pull you out is greater than you would need to lift a car.

Don’t believe everything you see in the movies, though, because although you might become stuck, it’s impossible to drown in quicksand: it’s twice as dense as you are, so you’ll only sink to waist height.

HOMEMADE LITMUS TEST

Chemicals that are either acids or bases (alkalis) can look very similar, so it can be hard to tell them apart. In order to do so, chemists use substances called indicators that change color accordingly. The most famous example is litmus, which is made from lichens, but other plants and vegetables also contain pigments that can work the same way.

♦ Take about a quarter of a red cabbage.

♦ Use a shredder or a knife to slice the cabbage into small pieces.

♦ Transfer these to a bowl and add a small amount of water (but not enough to cover the cabbage).

♦ Crush the cabbage with a wooden spoon, and then pour the result through a sieve, keeping just the liquid. It should be a purple-blue color. This is your indicator test solution.

♦ Add small amounts of this indicator solution to a series of plastic cups or glasses—you need at least three.

♦ Aim to keep one cup of indicator as your “control.” Don’t add anything to this cup so that you can use it as a record of the starting color of the solution.

♦ To one of your other cups, add a teaspoonful of lemon juice or vinegar, and to another cup a teaspoonful of baking soda (bicarbonate of soda).

♦ Swirl the cups to mix the contents, and then watch what happens. The liquid in the vinegar (or lemon juice) cup should turn pink, and the liquid in the baking soda cup should turn dark blue.

WHY does it work?

It’s down to a discovery first made by the seventeenth-century chemist Robert Boyle, who coined the terms “acid” and “alkali” (or “base”) and who also invented the litmus test.

Red cabbage contains a water-soluble pigment called a flavin, part of a family of chemicals called anthocyanins. These are large molecules consisting of several linked rings of atoms that share their electrons amongst themselves. These electrons absorb certain wavelengths of visible light but reflect others. The reflected light is what gives the chemical its characteristic color.

When an acid is added, such as the acetic acid in vinegar or the citric acid in lemon juice, the acid adds extra hydrogen (known as hydrogen ions) to some of the oxygen atoms in the anthocyanin molecule.

This prevents some of the electrons from being shared, causing them to soak up more blue light. Since white light is a mixture of wavelengths ranging from blue to red, removing more of the blue light has the effect of making the chemical look more red.

What about when an alkali is added, such as baking soda? Unlike acids, that try to give hydrogen ions to other chemicals, alkalis or bases try to remove them. When baking soda, that contains sodium bicarbonate, is added to the cabbage indicator, it steals some of the hydrogen from the molecule. To make up for the loss of the hydrogen, the anthocyanin shares out more of its electrons around the molecule. This causes it to absorb more red light and to reflect more blue light, so it looks blue.

HOW does this apply to the real world?

Most of the colors you see in nature are thanks to the reaction you’ve reproduced in this experiment. This was discovered by the German chemist and 1920 Nobel prizewinner Richard Willstätter. He showed that roses are red and violets are blue not because they make different pigments but because they alter the acidity or alkalinity of their petals. This, in turn, changes the color of their anthocyanins, altering the color of the flower.

SOME OTHER THINGS TO TRY

Use your indicator solution to test other household substances. Good things to try are soap, sour milk, cream of tartar, carbonated water, and a soft drink. Also, prove that the indicator effect is reversible. Add something acidic to your indicator, and then add something alkaline.

Try other plants from the garden. Which of them work as indicators? Is there anything that connects the ones that do?

IRON OUT YOUR CEREAL

“Fortified with iron” says the side of the cereal box. But is there really iron in there and, if so, what does it do, and can you see it?

♦ For this experiment, you will need some breakfast cereal, preferably one claiming to be high in iron, a mortar and pestle, or something similar with which to crush it, and a strong magnet or pair of magnets.

♦ Take a cupful of the cereal and grind it to a fine powder.

♦ Add one of the magnets and mix it round in the cereal dust.

♦ Retrieve the magnet and study the surface.

♦ You should be able to see fine grains of cereal sticking to it, and if you bring a second (stronger) magnet near to the first, the particles will jump onto the second magnet.

WHY does it work?