Following our free-style potions session, this week we played with dissolving solids in water. Our focus this time was on exploring rather than scientific accuracy – I wanted the kids’ imaginations and curiosity to be sparked.

Set up

* bowls containing a variety of solids, including instant coffee, gravy granules, salt, caster sugar, sand, flour, sprinkles (two types) and gummy bears (guaranteed to elicit interest)

* large jug of hot water

* large jug of cold water

* glass jars & glasses

* teaspoons

I also printed off a chart for C(9) and J(8) to record their results if they wanted to.

What we did

Before I gave them the chart, I invited the children to use their senses to guess what each of the substances was. The gravy granules evoked a lot of interest here, the smell reminding them of their favourite snacks. (I wonder if they’ll be more excited next time I serve gravy.)

We talked about the scientific method and I suggested that before they added each substance to water, they make a guess which they needn’t share out loud as to whether or not it would dissolve. (The secret hypothesis is a safeguard against my perfectionist child melting down mid-experiment.)

They then took turns putting a teaspoon of each substance into water (first cold then hot), observing, stirring and then recording their results.

Highlights

* The sprinkles were interesting. First they lost their colour, turning the water cloudy. Then after a few minutes they dissolved. C(9) guessed that the colouring was very soluble, and that the sprinkles were made of sugar so also dissolved, but more slowly.

* They loved watching the coffee granules dissolve rapidly in the hot water.

* The gummy bears prompted a couple of spin-off experiments of their own. Firstly the children noticed that they gave off little flecks in the hot water. Then they observed that after being in water for a while, they lost the colour around their edges and expanded slightly, so it was decided to leave them overnight. (I put them in the fridge, anticipating a future taste-test request.) More on this in a separate post.

* They liked watching the gravy vortex created by rapid stirring.

What we might do differently next time

* Both children added every substance to both hot and cold water, which involved a lot of me running around washing out jars. Next time I would suggest they take turns doing the hot or cold water. Or have more jars.

* More importantly, while I was busy washing up jars, the children decided salt wasn’t soluble! They hadn’t given it enough time to dissolve. We repeated this part of the experiment later and talked about how we don’t see and feel bits of salt around us when we swim in the sea!

* I might provide a measuring beaker and spoon, so they could use the same amounts of solid and water each time. We could time how long the solids take to dissolve in hot water compared with cold.

The science

When a solid dissolves, it breaks into tiny pieces, so small that you can’t see them in the water. We call the mixture of solid and water a “solution”. Solutions may be coloured (like coffee), but they are always transparent.

We also talked about how hot water molecules move more quickly so come into contact with solid particles more often, which is why solids dissolve more quickly in hot water than cold.

What next?

Over our next few “potions” session we’ll be experimenting with ways of separating mixtures and solutions.

I’ve been wanting to set up a free-style “potions” invitation for my kids ever since I came across 10 More Magic Potions.

Since we gave up following a science curriculum we’ve played with density, slime, fizzy fountains, elephant’s toothpaste and red cabbage indicator among other things. But, perhaps because we didn’t homeschool from the start, I’ve never set things up quite this way before, and I wanted to give C(9) and J(8) a serious chance to play before we move on to any more specific “potions” experiments (dissolving, separating liquids etc).

A visit on Wednesday to Professor Snape’s potions classroom at the Harry Potter Warner Bros Studios was just the catalyst I needed!

Here’s what I set out:

Equipment

* test tubes (large and small)

* plastic bowls

* funnels

* coffee filter papers

* sieves

* whisks

* long-handled spoons

* popsicle sticks

* measuring beakers

* pipettes, eye droppers & a medicine syringe

* conical flasks

* lab glasses

“Ingredients”

* bottles of coloured water

* plain water

* bubble mixture

* cornflour

* salt

* sand

* mustard powder

* bicarbonate of soda

* old tube of hair conditioner

* old bath bombs

I was going to set up outside and suggest that the children collect additional supplies from the garden – dirt, leaves, and the like – but it started raining so we stayed at the kitchen table.

I made sure we had plenty of kitchen paper and old towels on hand: one of the many learning points was how much liquid does (and doesn’t!) fit into different shaped containers.

Once I’d shown the children the supplies, I left them to it and busied myself taking photos and notes.

I didn’t put out food colouring in the interests of economy, but provided it at C(9)’s request – she wanted a more intense colour without water.

The children had so much fun doing this, and I loved watching them learn as they played.  Free-style potions has something for everyone!

“Elephant’s toothpaste” is a wonderful illustration of the power of a catalyst to speed up a reaction. It’s also very cool, and anything that shows kids how cool science is worth doing, right?

What You Need

• 6% Hydrogen peroxide (1/2 cup)
• Yeast (1 tsp)
• Hot water (2 tbsp approx) in a small dish
• Food colouring
• Washing-up liquid (dish soap)
• Empty soda/water bottle (small)
• Tray to stand the bottle on to catch the foam
• Funnel (optional)

What You Do

1. Pour the hydrogen peroxide into the bottle
2. Mix the yeast into the water
3. Add the washing up liquid and food colouring to the hydrogen peroxide in the bottle
4. Add the yeast mixture to the bottle
5. Stand back and admire the reaction!

What Happened

The photos say it all! We had enough hydrogen peroxide in our £2.74 bottle to have two goes.  Afterwards I gave the children a bowl each to mix up the red and green foam.

The Scientific Explanation

Hydrogen peroxide naturally breaks down over time into water and oxygen. Catalase, the enzyme in yeast, acts as a catalyst to speed up the reaction.

The washing-up liquid joins with the oxygen to make an abundance of foam.  And – as with so many of our homeschool science projects – the food colouring just makes the whole thing look even cooler!

What We Might Do Differently Next Time

I get so excited doing experiments like this that there are always a few things I forget to mention to the kids. (But that’s ok because then we have an excuse to do it again. :-))

I would point out next time that during the reaction, the bottle gets warm and steam is produced from the water, because this is an exothermic (heat-producing) reaction.

I would also mention that although a catalyst speeds up a chemical reaction, it is left unchanged itself:  the dissolved yeast is left in the bottle.

The Book and the Hat-Tip

Elephant toothpaste is well set-out in our favourite Science Experiments book, but I followed the instructions I found at another mum’s blog (unfortunately her blog is no longer live).  Where there’s a choice, I prefer to follow a mum’s personal experience when it comes to learning fun with kids!

Do you notice our safety glasses? Not strictly necessary here, but they definitely remind us we’re Real Scientists!

For more fun science ideas, visit Science Sunday at Adventures In Mommydom.

Do kids want to learn about acids and bases? If they’re like my kids then probably yes in theory – but in practice, “Not right now, thanks Mummy, I’m just finishing this game on Grid Club/making this cardboard helmet/playing my guitar”.

Do kids want to play with colourful potions? Absolutely! And once you’ve ignited their curiosity, of course they’ll want to know all about it!

Bring on the red cabbage and those old faithfuls, vinegar and bicarbonate of soda…

What You Need

• Red cabbage (we used half a head)
• Water (the book says to used distilled water, but we used tap)
• Saucepan
• Stove Top / Hot Plate
• Glass jars/glasses etc (to pour the cabbage water into)
• Household substances to test eg vinegar, lemon juice, bicarbonate of soda, soap
• Marker pen or dry wipe marker (optional) to label the jars

What You Do

1. Roughly chop the cabbage and boil it in water for about 10 minutes.
2. Drain (and discard/eat) the cabbage, reserving the water.
3. Pour the water into as many jars/glasses as you have substances to test, plus one as a control.
4. Add one substance (e.g. lemon juice) to each jar of purple cabbage water. Label the jar so you don’t forget what you’ve added.
5. Observe any colour change, comparing against the control cabbage water (to which nothing has been added).

What Happened

The water the cabbage has been boiled in is dark purple.

C and J both chose to add vinegar  to their first jar, which turned the cabbage water a pinkish colour. Then they predicted (proper science!) what would happen when they added lemon juice, and were happy to confirm their hypothesis that lemon juice also turned the water pink.

The effect of adding bicarbonate of soda was more subtle.  We had to scoop up a small amount of the liquid with a teaspoon to fully appreciate the change – the water took on a blueish hue.

Soap turned the water very slightly blue, and soy sauce had no noticeable effect.

What We Might Do Next Time

What we forgot to try (there’s always something!) is adding vinegar or lemon juice to our bicarbonate of soda water.  If you get the quantities right, this should turn the water back to the original (purple cabbage) water colour.

There are also lots of other substances we might test – orange juice, milk, Coca-Cola, tomato sauce…

You can also dip paper into your cabbage water to make your own indicator paper. Use this to test acids and bases once you’ve discarded your cabbage water.

How Does It Work?

I’ll hand you over to the Science Experiments book here:

“An acid is a substance that produces positively charged particles made of oxygen and hydrogen, called hydronium ions, when dissolved in water…

A base is the chemical opposite of an acid.  Bases produce negatively charged particles in water, called hydroxyl ions….

Cabbage water [is an indicator, which means it shows] whether a liquid is acidic or basic. [It changes] colour because the structure of [its] molecules changes depending on the amount of hydronium or hydroxyl present.”

Taking It One Step Further

For this you’ll need a pack of pH-testing litmus paper (£2.76 on Amazon).

I gave the children a book of litmus paper and they dipped a fresh piece in each of their cabbage water jars. They compared the colour the paper turned with the colour scale on the book, to obtain a pH value.

I explained that pH is a measure of the acidity or alkalinity of a solution. (Bases that dissolve in water are called alkalis.) Acids have low pH’s, alkalis have higher pH’s.

C noticed by testing with litmus paper that our soy sauce solution was very slightly acidic.

Has anyone else tried this? Do leave a comment to let me know how it went or if you know of any other fun experiements with acids and bases!

More Hands-On Science Posts

How to Make Slime and Plastic

Fizzy Fountains

Copper-Plating a Nail

Thanks to Adventures In Mommydom for hosting Science Sunday!