So, what is a fluid? It is a substance that flows or deforms when stress is applied to it. It can be a gas, liquid, or plasma. So, as you can probably imagine it is quite a broad party theme. However, I want the demos to focus on fun, strange, messy fluids that’ll keep the kids gasping for more.
When people think a fluid is behaving ‘normally’ they think of a Newtonian fluid (yes, named after Sir Isaac Newton, who made the discovery). This means its viscosity (flow) is constant unless a change in temperature or pressure occurs. This can be easily demonstrated with water. However, non-Newtonian fluids are funny and great at parties and that is because they behave in rather unusual ways…. Below are a couple of examples:
Cornstarch and water (Oobleck)
This is a really simple way to show a funny fluid at work and more importantly the materials can all be found in your kitchen. All you need is:
– a bowl
– food dye (not necessary but if you want to add colour to your oobleck add a bit of colouring to the water before you mix)
– spoon (or you can use your hands)
In a large bowl add your packet of cornstarch, then gradually add your water mixing the cornstarch constantly. I really would recommend using your hands as you get a better feel of what is going on and you don’t want to over do it with the water. I find there isn’t an exact ratio (and people swear by different things) but you may want to start with 1cup of cornstarch to 1/2 a cup of water. As you add the water you’ll notice the consistency change and things will feel gooey.
You want to get to the point where you can move your hand gently around in the bowl and it’ll be like a liquid but once you punch the mixture it is like a solid. You will also be able to pick up a chunk of goo and it you roll it really quickly in your hands it becomes a ball but as soon as you stop rolling it’ll melt into a liquid. This phenomenon occurs because the cornstarch molecules are held in a suspension (they don’t dissolve) and when you apply a force really quickly the molecules don’t have time to move smoothly past each other but instead ‘lock-up’.
There are loads of videos on the internet so you will have no trouble finding what the fluid should look like. Here is one of Steve Spangler’s
– 1tsp borax
– 3tsp PVA glue
– food colouring (again optional)
– 2 small bowls or cups
Add the borax to 100ml of water – stirring it so it dissolves. In the other bowl add the PVA and food colouring. Then add the borax-water mixture, stirring continuously. Ask the kids to feel the bowl and they should feel it getting hot and that is because a chemical reaction is taking place and heat is being released.
In this non-Newtonian fluid the borax reacts with the PVA, forming a huge cross-linked molecule. These big molecules are known as polymers. The molecules can’t easily slide past one another, hence why the fluid is no longer runny.
This is something so easy for the kids to make themselves. Once done, you can put their slime in a zip-lock bag and they can take it home in their party bags for more mess and mayhem there.
When I did this at parties we used the borax but I’ve seen on the internet there are ways to do it without the borax.
There is so much fun you can have with non-Newtonian fluids and the cool thing is they are actually everywhere – ketchup, snot, blood, custard, and toothpaste!
Love, love, love this – it is magic sand.
Just look at how all the sand quickly clumps together when poured into water – it hates the stuff. There are so many great fun experiments kids can do with this stuff and I have found the perfect video to show you how to make it, explain the science and show you some cool demos!
Bubbles – detergent and water. To get the huge bubbles that don’t pop easily add a bit of glycerine.
Why not try making instant ice-cream for the kids (you could also get them to make their own but it is best they are supervised by an adult as dry ice can burn). It is really cool stuff, you can make your own flavours and as well as fun it looks like you’re a witch with a caldron – the dry ice sublimes (goes from sold straight to gas).
This video shows a really easy way to make it (the guy in it can be slightly annoying – sorry).
As this is a fluid party I think a great cake would be one which has molten chocolate or some sort of sweet goo inside. When you cut into the cake all the nice goo comes out and if it is chocolate it’ll gradually solidify – yum!
As this is about fluids and everyone things of liquid as a fluid, you could get some funny shaped bottles and add coloured water into them and set them around the house. You could play around with density and use different liquids (of differing colours) stacked on top of one another giving a the illusion of a funny fluid. You can be as creative as you like with this (make the liquids fluoresce and darken the lights so you have an eerie mood).
You can add plasma lamps around the room too. They can be easily found in places like Walmart and kids love putting their hands on them and seeing what happens!