Kitchen Science - Guest Post by Dr Jo Science Solutions

British Science Week 2020 is fast approaching (6-15 March) so this is a great time to be thinking about – and doing – science!



There are lots of ‘whizzy’ science experiments on the internet, often with lots of ‘wow!’ but not much substance behind them; there is little explanation or understanding of what is happening, or why. That’s not to say that real science isn’t fun or exciting – it absolutely is! Learning – discovering new things – is a joy, and there are often ‘wow!’ moments along the way. I’m just keen on finding out the ‘why’ as well.

Sometimes people can feel a little daunted by science, but you needn’t be. It really is just about being curious, asking questions and wondering, and observing what is happening. A little background knowledge is useful, though, to help ask the right questions and to avoid misconceptions.

You don’t need a chemistry lab to do ‘science’ - as well as there being so much to discover in the natural world, there are myriad experiments and investigations that you can carry out at home using easy to source ‘kitchen science’. The key is to build up observations and understanding from simple principles. This blog post is by no means exhaustive, and there are many additional explorations you can try from each one of these suggestions and more! I could have gone on and on, but there’s only so much time; come and be curious and discover and few things with Dr Jo and see where it takes you...

Solids, liquids and gases

You could start with observations about solids, liquids and gases and explore these different states of matter: compare ice, water and steam. What do they look like? Feel like? (Don’t do this with steam from the kettle, it’s hot! – but you could look at steam in the shower: what happens when the warm steam (water vapour) condenses on the cold bathroom mirror? Why not see if you can find out more about the same molecules are arranged in different ways in each state.



Go outside after it rains and look at the puddles (or make your own puddles with a watering can!). On a warm or sunny day, what happens to those puddles? Could you draw around the puddles in chalk and track what happens throughout the day?

Try making a miniature model of the water cycle by putting some water in a sealed plastic bag and taping it to a window that catches the sun. As the water warms up, observe what happens inside the bag over a few days. You should see that the water evaporates, then condenses and drips back down as it cools, just like rain.



Changing states

Explore changes of state by observing what happens when you heat ice, or freeze water. Can you change them back again? Make solids liquid or liquids solid? Are the changes reversible, or irreversible? What about other materials? What happens when you heat butter? Or wax? Or eggs? Can you change it back? Is it the same as before? Physical changes of state are usually reversible, whereas a chemical reaction or change is often irreversible – the protein in the egg is denatured as it is heated, changing the structure of the peptides irreversibly so you cannot un-cook an egg!

Quick ice cream

Another fun way to explore changes of state and reversible and irreversible changes is to make ice cream in bag! Put ice and salt in one plastic bag and then put milk and milkshake powder (or fruit and cream, try lots of variations and see which works best) in a second bag and seal it well. Place the milkshake bag inside the ice bag. The salt lowers the freezing point of the ice. It will start to melt, but due to some magic the physical interactions of the molecules, the temperature will actually decrease. By gently bouncing the bag up and down (take care not to let any milkshake leak out or be too vigorous or you risk getting salt into the ice cream), the milkshake is churned as it is cooled by the ice to create a soft scoop ice cream in just a few minutes.


There are multiple changes happening and lots to think about here: an interaction between the salt and the ice; the salt dissolving in the water; the ice changes from a solid into a liquid; the milk changes from liquid to a solid; the milkshake powder is dissolved in the milk; the ice cream gets eaten and digested quite quickly too! Which of these changes are reversible? Why?

There are lots more explorations of solids, liquids and gases, including a nice sequence of investigations to build observations on chemical reactions:

Making sherbert

This simple investigation also involves developing simple measuring skills.

1 teaspoon sodium bicarbonate

1 teaspoon citric acid (a food preservative, find it in the pharmacy, often used when making elderflower cordial)

7 teaspoons icing sugar

Mix together carefully to ensure an even distribution and then place a small amount on the tongue. What happens? What can you feel? The citric acid and sodium bicarbonate combine in the presence of water (the saliva in your mouth) to create bubbles of carbon dioxide, which gives a fizzing sensation on the tongue. The icing sugar is just there to make it taste nice! I normally wouldn’t advocate eating your experiments, or even eating food or touching your mouth, eyes and face while doing science, but this one is a special case. Some of the experiments in this blog post could really sting if they got in your eyes, and might irritate your skin. Always make sure you stay safe.


Bicarbonate and vinegar ‘volcanoes’

This acid-alkali chemical reaction can be explored further in the popular ‘volcano’ reaction. Take care to explain that this ‘eruption’ might resemble the look of an active volcano, but the reaction is not the same as the molten lava ejected under high pressure.

This looks great in a test tube, but a small glass or beaker, or small bottle will also work well.

1 teaspoon sodium bicarbonate

pour in a little vinegar or lemon juice (this has a less pungent smell!)

Instead of using solid (crystalline) citric acid, the acid in this acid-alkali reaction is found as a liquid in the lemon juice (citric acid) or vinegar (acetic acid). Bubbles of carbon dioxide are again produced and can be seen as the effervescent fizzing! This one isn’t for tasting!



You could try different quantities of sodium bicarbonate and vinegar to see what produces the most bubbles, or try testing other food and drink (such as juice) to see if they contain acids to react with the alkaline sodium bicarbonate.

pH indicator

Another way to test if food and drink (or other items) are acidic or alkaline, is to use a natural indicator. Extracting the anthocyanin pigment from red cabbage (you could also try purple leaves, beetroot, blueberries etc) by chopping it up, boiling and using the resulting liquid, gives a reliable indicator to test the pH (a measure of the acidity or alkalinity) of various liquids. The purple cabbage liquid will turn pink in the presence of an acid, such as vinegar, and blue-green in the presence of alkalis, such as sodium bicarbonate, detergent or soapy water. You could try different fruit juices, tap water and rain water. What colour do they turn the cabbage indicator? You could use test tubes or small pots or beakers if you have them, but small glasses will also work well.




Dancing raisins

Having made carbon dioxide gas bubbles in the acid-alkali reactions, you could also try exploring the properties of such bubbles. This is a great opportunity to slow down, observe really closely and ask lots of questions about what is happening, and why! Pour a tall glass of sparkling water or lemonade. The carbon dioxide gas is trapped under pressure in the liquid. Observe the bubbles. Where are they in the glass? What are they doing? The bubbles are congregating on the bottom and the sides of the glass as they are ‘seeded’ here by minor imperfections or bumps on the surface of the glass. This is called ‘nucleation’. Because the bubbles of carbon dioxide gas are less dense than the liquid, they float up towards the top (Note that unlike in Roald Dahl’s the BFG’s frobscottle drink, the bubbles go up rather than down!).

Drop one or two raisins into the glass and observe closely what happens. What happens to the raisin? Where does it go? Does it float or sink? Look at the bubbles. Can you see them forming on the outside of the raisin? The surface of the raisin has minor imperfections which act as nucleation points to attract the bubbles of gas. As more bubbles form on the raisin, they act like buoyancy aids, making the combined structure less dense than the liquid so it rises up to the surface. When the bubbles reach the surface, they burst, the raisin is more dense than the liquid and so it sinks back down.



Soda fountain

The soda fountain - or coke and mentoes reaction - is a popular experiment, where the science is often missed! By observing and thinking about the dancing raisins first, it makes it much easier to understand what is happening in the soda fountain. Bubbles of carbon dioxide are trapped in the fizzy drink as before. Instead of raisins, this time mint imperials or mentoes sweets are used. The surface of these sweets are also covered in minor imperfections to act as nucleation points, attracting the bubbles of carbon dioxide. However, multiple mentoes are dropped into the bottle at once – preferably via a tube which you can easily make out of card, or stick several mentoes together along a length of sticky tape or indeed you can buy a ‘geyser’ tube for this purpose – and the full bottle of fizzy drink is already under pressure and the bubbles have limited options about where to go. The pressure builds up and the bubbles very quickly force their way out of the narrow top of the bottle. I recommend standing well back for this one!


You could try extending the investigation by comparing different fizzy drinks: which produces the highest fountain? Cola, lemonade, fizzy orange etc. Does diet or full sugar fizzy drink work better? Does temperature of the fizzy drink make a difference? How many mentoes can you fit in? Does it change the height of the ‘fountain’? What’s the best way to get the mentoes into the bottle?

Sweet rainbows

Following on with the sweets theme, there are lots of investigations we can do. A classic one, popular with children and adults alike, is looking at what happens to skittles in water. Place a few skittles in a shallow dish or saucer – arrange however you like: around the edge, different colours, in a shape or pattern. Then carefully pour water over them to just cover the skittles (take care not to disturb the sweets) and keep it as still as possible trying not to jog or knock the table or dish. Now comes the patience as you watch and wait.




The coating of the sweets will dissolve in the water. What do you notice? Can you see the colour at the bottom of the water? Throughout the water? Just at the top of the water? Why do you think this is? Notice what happens where two colours meet. Do they mix? Look closely at where they sit in the water. What do you notice about the layers of colour? Why do you think this might be? Hint: Density is involved here. Keep watching. If you have entirely covered the sweets, you might notice that there are little white flecks floating on the surface of the water. What do you think they might be? Fun fact: Whilst skittles are vegetarian, they aren’t vegan as the ‘S’ shape on each sweet is made with beeswax. As the wax is immiscible in water and is less dense than the liquid, it floats on the surface.


What happens if you use cold water or warm water? Will it make a difference? How could you tell?


Chromatography

Another great investigation using sweets is to extract the colour from M&Ms (they work much better than smarties as the colours are artificial, unlike smarties’ natural colourings) and separate them using a technique called chromatography. Mixed colours can be separated into the constituent colours – from sweets, from felt tip pens, and even from colour extracted from plants. Place an M&M on some filter paper, coffee filter paper, thick kitchen roll or blotting paper balanced on top of a cup and drop a few drops of water over the M&M so that it’s just sitting in the water but isn’t saturated. The colour coating will start to dissolve. Add a couple more drops of water (using a pipette, syringe or even a small spoon. The syringes you get with children’s liquid medicines are great washed out and used for science investigations!) and watch as the coloured water spreads out on the filter paper. As the water spreads out, it takes the colour with it. The different colour molecules are different sizes, and so they travel more or less quickly through the paper, separating as the water moves outwards. The smaller molecules will move more easily through the paper so will travel further. Can you tell which colours are made up of smaller molecules?

You could also try this by dotting the colour from the wet M&M at the bottom of a strip of filter paper and allowing it to dry (add a few repeated layers of the colour), then place the very bottom of the paper just touching a little water in a glass or beaker. As the water is sucked up and travels up the absorbent paper, it takes the colour with it, separating the molecules as it goes. You could also try this with little dots of felt tip pen, or even grinding up different coloured leaves and using the colour to create dots – you could do this to investigate the different pigments in plants - such as the green pigment chlorophyll involved in photosynthesis – you might be surprised about the colours that you can see.




Sugary snacks

Heading back to sweet things in the kitchen, you could try doing some secondary research – reading the ingredients and nutritional information on packets of food and drinks, or use the internet to investigate how much sugar is in different food stuffs. Translate the amount of sugar in portions of different items into spoons of sugar and create a visual representation. Try looking at fizzy drinks, fruit juice, cereal bars and snacks and display the items next to the equivalent amount of sugar. You might be shocked to find so much sugar in some foods.



Density and viscosity

Whilst we’re looking at food items in the kitchen, how about testing different liquids for their viscosity. Try pouring - or using a syringe to drip - tomato ketchup, golden syrup, cooking oil and other liquids down a ramp and timing how fast they travel. The more viscous the liquid, the slower it will travel.


You could also look at the relative densities of liquids by layering them up in a tall glass or measuring cylinder. Liquids which are less dense will float on top of liquids which are more dense. What happens if you try water, oil, fruit juice and golden syrup? You could try adding different food colouring to some cold water and see what happens if you try to carefully layer boiling water on top. What happens? Do you think the densities will be different? Why?


Floating and sinking

Finally, how about going back-to-basics with floating and sinking investigations. In the bath, paddling pool, or even just a big bowl of water, try out a range of objects such as a toy car, hair clip, toothbrush, pine cone, orange etc and see if you think they will float or sink. Make a prediction before you try each item. Does it make a difference if an orange has the skin on, or it has been peeled? You could try using a piece of plasticine and moulding it into different shapes and see which ones float and which ones sink.

Which brings us back to the importance of just observing the everyday and wondering why….after all, The World Is Their Classroom!

About Dr Jo

Dr Jo is passionate about inspiring the next generation of scientists through engaging, hands-on, practical, curriculum-linked primary science workshops in schools, STEM clubs and home education groups. Dr Jo is a science communicator, teacher, trainer, public engagement and outreach specialist with a PhD in Neuroscience and a qualified primary school teacher. She has more than 20 years experience designing and delivering science workshops and activities for primary and secondary schools, FE and HE colleges and teacher professional development. Dr Jo has worked in academic research, the pharmaceutical industry, teaching and most recently supporting education through Dr Jo Science Solutions. She’s also quite keen on tea, cake and sunshine, spending time in nature and with her family!



Twitter.com/DrJoScience

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A note on single use plastics

Some of these experiments involve single use plastics, such as zip sealed bags. I’m always looking for ways to cut down my plastics use, and to use alternatives or re-use wherever possible. You could make the ice cream in a small bowl inside a larger bowl and carefully stir. The bowl containing the ice cream will need to be able to conduct, and not insulate, so that the cold can reach it – you could try a metal bowl (maybe wear gloves!), or a ceramic or glass bowl would work better than a plastic bowl (why do you think this is?). You could make the water cycle model inside a transparent sealed dish or pot instead of a plastic bag. Can you think of any other plastics alternatives?

Safety First

Please remember to be safe and minimise any risks. Think carefully before you do any experiments. Dr Jo is not responsible for your safety.



Comments

  1. I absolutely love this post. It is so much fun to see your adventures in science and how you teach your kids. It's beautiful! I'd love to see more kids learning like this - actually engaged and enjoying the learning experience. Your site title says it perfectly - the world is their classroom. Thanks for doing what you do! I applaud you! ♥

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