How much water can a disposable nappy soak up? Find out with this experiment, and learn about the amazing world of superabsorbent polymers at the same time!Suitable for kids aged 4+You Need:
What to do:
- Zip lock bag
- Small piece of a disposal nappy (cut about a 3x3cm square)
- Food colouring (optional)
- Put the nappy square into a zip lock bag and add some water (about enough to half cover the nappy square at the bottom of the bag). What happens?
- Add some more water. How does the nappy respond? How much water can you add before the nappy is unable to soak up the excess?
- Feel the nappy. Can you identify what is soaking up the water?
- What happens when you add salt to the nappy? Try adding some food colouring for a colourful effect. What are you left with if you leave the nappy to dry in the sun for a few days?
Why is it so?Disposable nappies contain superabsorbent polymers that love water, just like our growing beads and instant snow. The polymer can absorb many times its weight in water and grow up to 40 times its size. This keeps baby dry and happy! Superabsorbent polymers are composed of cross-linked molecules that have a high sodium content attracting water into the polymer system through a process called osmosis.
Soak a hard-boiled egg in vinegar to transform it into a rubbery egg that can bounce like a ballSuitable for kids aged 4+ with parental supervisionYou Need:
What to do:
- Hard-boiled egg
- Glass or jar, big enough to hold the egg
- Place the hard-boiled egg in the glass or jar.
- Pour enough vinegar into the jar to completely cover the egg. Look closely, what do you see? Can you see some tiny bubbles start to form on the shell? Why?
- When the shell has completely dissolved, after about 3 days or so, remove the egg from the jar and gently rinse it with tap water. How does it feel?
- Bounce your new rubber egg on a hard surface. How high does it bounce?
- As a further experiment, try soaking a raw egg in vinegar for 3-4 days, how does the raw egg compare to the hard-boiled egg soaked in vinegar? Gently squeeze the egg. How does it feel? We dont recommend you bounce this egg.
Why is it so?Vinegar is a weak acid (acetic acid) and reacts with the calcium carbonate eggshell to produce carbon dioxide gas (hence the bubbles that form). Eventually the calcium in the eggshells is completely broken down by the acid and become a soft rubbery texture.
Disappearing Ghost Crystals
Watch these hard crystals swell and grow into jelly-like pieces with water. Then amaze your friends when they disappear in water, or add some food colouring for cool effects. Welcome to the amazing world of superabsorbent polyemers!Suitable for kids aged 5+ with parental supervision. CAUTION
Ghost crystals are generally considered non-toxic and are safe for use around young children unless ingested. If ghost crystals are swallowed do not give liquids. Seek medical advice.You Need:
What to do:
- Water absorbing crystals (available from your local nursery or garden supply centre)
- Transparent cup, beaker or glass
- Food colouring (optional)
- Sprinkle a small amount of water absorbing crystals into a glass. You dont need many a flat teaspoon is plenty.
- Half fill the glass with water.
- Now watch. Your crystals will start grow as they absorb water. After a minute or so you will start to notice a difference in their size. Continue to monitor their growth at regular intervals. After 2 hours they will have fully grown.
- Take out a couple of crystals and investigate the change in their texture (now gel-like) and size.
- Fill the cup with water and watch the ghost crystals magically disappear. You may need to tip the crystals into a larger transparent glass to see them disappear completely.
- Drain the water and watch the crystals mysteriously reappear.
- Drain most of the water and place a few crystals on a paper towel. Leave them in the sun and monitor their decrease in size at regular intervals. They are re-usable!
- Try sprinkling some salt on the jelly-like crystals. What happens?
- Try growing some crystals in water with food colouring for a colourful effect.
Why is it so?Ghost crystals are made from a cross-linked polyacrylamide polymer allowing them to absorb so much water (95%) that they have the exact refractivity (how much light is bent) as water, and thus seem to disappear completely in water. They grow up to 200 x their original size in water. Ghost crystals have many real life applications. They are used in agriculture to retain water in soil, in horticulture and mining. They are also similar to the super absorbent polymer used in baby nappies.
Make your own hypnotic lava lamp with oil and water and a secret ingredient that makes it fizz and bubble.Suitable for kids aged 5+ with parental supervision. CAUTION
Remember Alka-Seltzer tablets are a medicine, do not ingest. Read the packet instructions for more information.You Need:
What to do:
- An empty soft drink bottle with cap, or clear jar/container with a lid
- Vegetable oil
- Alka-Seltzer tablets (from the supermarket)
- Food colouring
- Fill the bottle (or container) about full with vegetable oil.
- Carefully fill the rest of the bottle/container with water (nearly to the top but not overflowing). Why doesnt the water mix with the oil layer?
- Add about 10-15 drops of food colouring so the water is a nice deep vibrant colour. Why does the dye only colour the water?
- Break an Alka-Seltzer tablet into 6-8 pieces.
- Drop one of the Alka-Seltzer pieces into the bottle/container. What happens? When the fizzing stops add another piece. Then another its just like a lava lamp! Cool man!
- When you have finished with the Alka-Seltzer tablets and the bubbling has stopped, put the lid on the bottle/container and tip it back and forth. Watch the wave and blobs develop and combine. Shake the bottle/container. What happens? Does the water and oil stay mixed?
Why is it so?Oil and water dont mix the water molecules (highly charged hydrophilic compounds) do not like the oil molecules (hydrophobic long chains of carbon). Even when shaken, the oil breaks into smaller droplets so it might appear mixed, but isnt. When left undisturbed, the oil and water will eventually separate into distinct layers. Food dye only mixes with the water.
Water is heavier (more dense) than oil, so when the water is added to the bottle/container it sinks to the bottom.
The Alka-Seltzer tablets react with the water to make bubbles of carbon dioxide gas. These gas bubbles attach themselves to the blobs of coloured water taking them to the surface through the oil. When the bubbles pop at the surface, the blob of coloured water sinks back down to the bottom. Definitely a groovy lava lamp!
Ink Chromatography Is black really black?
Separate out all the colours that make up a black felt pen using a special technique called chromatography.Suitable for kids aged 7+You Need:
What to do:
- Filter or blotting paper (a coffee filter works well) cut into strips (approx. 1.5cm wide and just short of the length of the cup)
- Transparent glass or plastic cup
- Icy pole stick
- 2 x black felt pens
- Take a pen and draw a horizontal line near the bottom of two strips of filter paper. Use a different pen for each strip. You can test more than two pens on other strips if you like.
- Tape the strips side by side to an icy pole stick so they are hanging vertically (like clothes on a clothes line).
- Suspend the icy pole stick across the top of a cup/glass so that the paper strips hang into the cup/glass.
- Being careful not to wet the paper strips, pour enough water into the cup/glass so the very bottom of the paper strips (but not the ink line) hang in the water. < li>
- Now watch and wait. When the water has just about reached the top, remove the paper strips and leave to dry. < li>
Why is it so?The water moves up the filter paper (against the force of gravity) through capillary action due to the tiny pores or tubes in the paper. The ink in black felt pens is a mixture of different coloured chemicals. As the water moves over the black pen lines some chemicals dissolve easier in water and spread up the blotting paper, creating a unique pattern. This is a good way to analyse the ink in a mystery note and find out which pen (and who wrote the note) by comparing the resultant colour patterns. It is an example of a science lab technique called chromatography, which is used to separate the components of a mixture. Although there are various chromatography methods, it always involves passing a mixture in a moving phase through a still or stationary phase.
Gas Flame Detection
Detect Carbon Dioxide gas with a candle flame. Will the flame get smaller, bigger, snuff out, change colour? How the flame behaves tells you the type of invisible gas present.Suitable for kids aged 10+ with parental supervisionCAUTIONThis experiment requires use of an open candle flame. Please exercise caution, and only perform under adult supervision. It also requires the use of a knife to cut a candle. This task should only be undertaken by an adult.You Need:
What to do:
- 2-3cm candle piece with wick (have an adult cut the piece using a knife from an ordinary household candle)
- Aluminium foil patty pan
- Piece of wire about 40cm in length
- Chop Stick or similar
- Glass jar, preferably with a wide mouth
- Baking soda
- Small measuring cup to measure 30ml
- First, prepare the candle holder. Cut a foil patty pan down its side and along its base to the centre point with scissors. Place the candle on the pan, and slide the cut sides over each other to adjust the pan size and have it fit snuggly around the candle.
- Make a loop at one end of the wire and place it over the candle and patty pan. Twist it on itself to secure the candle and patty pan tightly (a bit like a lasso).
- Twist the other end of the wire around the end of the chop stick a few times. The holder should now look a bit like a fishing rod. With the chop stick as the handle, the wire as the line and the candle as the bait.
- Measure out 30mls of vinegar and pour it into the glass jar.
- Add one heaped spoon of baking soda. Watch it fizz and bubble. The fizz and bubbles are caused by a gas produced when these two chemicals are mixed (chemical reaction), but we dont know what this invisible gas is.
- To find out, have an adult light the candle in the candle holder. You can then lower the lit candle into the jar. How does the flame respond in the presence of this new gas? Some possibilities to think about: oxygen will make the flame grow bigger, nitrogen will result in no change to the flame (approx. 78% of our air is composed of nitrogen), argon will cause the flame to shrink, carbon dioxide will snuff out the flame. So, what gas is made when vinegar and baking soda are mixed?
- Have a few tries at lowering the flame into the jar (re-lighting if necessary). A bit of a challenge: can you lower the candle in and pull it out before the flame snuffs out? Eventually the flame stays alight when you lower it into the jar. Why?
Why is it so?When vinegar and baking soda are mixed a chemical reaction occurs that results in carbon dioxide gas formation. The fizz and bubbles tells you its a gas, but how can you demonstrate that it is, in fact, carbon dioxide gas? Its interesting to think about how scientists work with matter thats invisible like a gas, and this is a good activity to show one way of working and identifying gasses. How the flame responds will indicate the type of gas made. Think about the possibilities - oxygen, argon, nitrogen, carbon dioxide all gasses found in air. The flame snuffs out telling you that indeed the gas in the jar produced by mixing vinegar and baking soda is carbon dioxide. After a while, the flame stops going out because the chemical reaction has finished and no more carbon dioxide gas is being made to put out the candle.
Make A Gelatin Disc
Best known for making jelly, gelatin is a fascinating substance that is used as a gelling agent not just in food, but in many other things. Heres how to make your very own gelatin product that can be used in further experiments or in some very cool artwork.Suitable for kids aged 5 +CAUTION This experiment requires the use of a small amount of hot water. This should be handled with care under the supervision of an adult.You Need:
What to do:
- Small round mould (the underside of a jar lid works well)
- 3 x teaspoons of gelatin
- Cup or glass
- Spoon or icy pole stick
- Food dye
- 40mls of hot water
- Squeeze a drop or two of coloured food dye into the hot water and mix with a spoon or icy pole stick.
- Place 3 teaspoons of gelatin in a cup or glass.
- Pour the coloured hot water into the cup with gelatin and mix gently with the icy pole stick or spoon.
- Before the gelatin-water mix cools down and starts to set, you need to pour the mixture into your mould. Pour a thin layer into the mould, trying to avoid bubbles and mess. li>
- Leave it to set. It will take a fairly short time for the gelatin to set like jelly (as soon as the mixture is cool), but will take 3 to 5 days to dry out completely and become a hard gelatin disc. li>
- Once it is hard and dry, remove the gelatin disc from the mould.
- You can continue to experiment with your gelatin disc. Try making 4 or so discs and placing them in various locations for a couple of weeks (freezer, bathroom or other humid environment, bury underground, hot dry spot). Or you may like to use your discs in some very cool art work mobiles, or as coloured film in some homemade binoculars/glasses. li>
Why is it so?Gelatin is a colourless, flavourless solid substance derived from the collagen inside animals skin and bones. Commonly used as a gelling agent in food, it also has lots of other uses. Gelatin is found in nearly all photographic films and papers, it makes up the shells of pharmaceutical capsules to make them easier to swallow, and believe it or not, even synchronized swimmers use gelatin to hold their hair in place during their routines because it will not dissolve in cold water. The gelatin discs in this experiment should grow mould on them when placed for any length of time in a humid environment like a bathroom. They grow mould because gelatin is biodegradable and will rot away in soil becoming food for plants and mini beasts. The biodegradable properties of gelatin are useful to explore during a sustainability and environmental unit.
Make some stunning chocolate leaves as a novel and delicious way to learn about the changing states of matter.Suitable for kids aged 5+ with parental supervisionCAUTIONThis science activity involves the use of boiling water. Hot water must only be handled by an adult.You Need:
What to do:
- Metal or heat resistant bowl
- Wooden spoon or similar
- Large non-poisonous leaves (rose, ivy, mample or lemon leaves work well)
- Boiling water
- Clean paintbrush
- Wash the leaves and dry them gently, careful not to damage or bruise them.
- Have an adult pour some boiling water into the saucepan.
- Ask an adult to carefully place the bowl inside the pan (be sure not to get any hot water in the bowl).
- Break the chocolate into the bowl. How does the chocolate behave in the heated bowl? Stir the chocolate and watch it melt and change from a solid state to a thick (or viscous) liquid.
- Have an adult remove the bowl of chocolate from the hot saucepan and place it on the table or bench.
- Use the paintbrush to paint a layer of chocolate on the underside (the veiny side) of the leaves. Allow to cool (chocolate side up) and set. You may want to speed up this process in the fridge. Carefully peel away the real leaves to reveal your gorgeous new solid chocolate leaves.
Why is it so?This is an interesting and unique approach to teaching about the changing states of matter. Instead of using water as the model, you use the very engaging (and yummy) chocolate. Students will watch solid chocolate change to a liquid with the application of heat. They will then see the chocolate change back into the solid state when it cools down. Use this activity as a springboard to talk about the molecular arrangement of solids, liquids and gases and how temperature changes affect the molecule movements.
Make water glow eerily under a black light using the fluorescent dye found in highlighters. Glowing water can create some exciting special effects when used in fountains, or use it to transfer glow to bubbles, ice and slime.Suitable for kids aged 8 + with parental supervisionCAUTIONThis science activity involves the use of a sharp knife to cut open a highlighter pen and the ink-soaked felt inside the highlighter. This must only be done by an adult.You Need:
What to do:
- Yellow highlighter felt pen
- UV light, or black light
- Clear glass or container
- Prise off the back of a highlighter pen, or if this is not possible, have an adult carefully cut the pen in half with a sharp knife.
- Pour some tap water into the glass or container.
- Wearing the gloves, pull out the ink-soaked felt that is inside the cut pen. Although nontoxic, the gloves will protect your fingers from being stained with the fluorescent dye.
- Soak the felt in the container with water for an hour or so. With the gloves on, squeeze the felt until almost all the ink has been transferred to the water.
- Turn on the black light and watch your water glow an eerie green.
- Use the water to transfer glow to any water based experiments or activities, like making slime, ice or bubbles. Tonic water also glows under UV light, so is great to use in edible glow experiments, like making glowing jelly.
Why is it so?Tonic water and highlighters glow under black light because they contain fluorescent chemicals. These chemicals absorb light and then release it back. In this case they absorb highly energetic invisible UV light and release less energetic but visible light. The water is transparent so it is easy to colour with these glowing chemicals. The glowing water can be reused again and again and will never lose its glow.
This COOL chemical reaction spews froth and foam everywhere. Just like a gigantic tube of toothpaste fit for an elephant.Suitable for kids aged 5+ with parental supervision.You Need:
NOTEThe best part of this chemical reaction is that it makes a BIG mess. We have listed safety goggles, smock, and trays in the equipment section to contain the foaming mess. Avoid getting hydrogen peroxide on the skin and follow all instructions on the container.What to do:
- An empty soft drink bottle (600mL size works best)
- cup of 6% hydrogen peroxide solution (purchased from a hairdresser/beauty supply store or chemist)
- Squirt of dishwashing liquid
- 4 drops of food colouring
- 1 teaspoon of dry bakers yeast dissolved in approximately 2 tablespoons of warm/hot water
- Safety goggles
- Lab smock (optional)
- Tray or foil cake tin to contain mess (optional)
- Put on your smock and safety goggles.
- Set out all the chemicals needed for this chemical reaction in front of you tin or tray to contain mess (optional), empty plastic bottle, dishwashing liquid, food colouring, peroxide and dissolved yeast. An organised scientist is a good scientist
- Stand the bottle in the tray if you are using one. Using the funnel, pour the hydrogen peroxide into the bottle and 4 drops of food colouring.
- Then add a squirt of detergent to the bottle.
- Now for the fun bit! Pour in the yeast mixture and quickly remove the funnel. Wow! Feel the bottle. What has changed during the chemical reaction? The warm foam is safe to play with (its just soap, water and oxygen bubbles).
Why is it so?Look at that oozing luscious toothpaste foam. What a wonderful chemical reaction! The chemical symbol for hydrogen peroxide is very similar to water except it has 2 oxygen atoms instead of 1. Hydrogen peroxide molecules are very unstable and naturally breakdown into water and oxygen gas. A small amount of heat is also released as it is an exothermic reaction. Yeast is the catalyst in this reaction, and makes the peroxide molecule release its oxygen atom faster. All the fix and foam is caused by the quickly released oxygen gas. The foam is safe to play with - it just contains oxygen bubbles, soap and water. Enjoy!