Little Lab

Jumping in puddles, making mud pies, getting cake batter everywhere: getting messy is perhaps the best part of being a child.  Today eight wonderful minds excited about science descended upon Saint George’s Hall to do just that.

We began the day by discussing the states of matter, but before we could do this we had to define what exactly “matter” meant.  Once we all agreed that matter is what makes up everything around us, from the air we breath to the chairs we were sitting on, it was a bit easier to guess what the states of matter might be.  Once someone mentioned gas, the other two, liquid and solid, followed quickly after.

States of Matter

A non-Newtonian fluid is an object that doesn’t quite fit into the traditional definitions of gas, liquid, or solid; it changes its state, not through temperature, but instead through force.   There are many different types of non-Newtonian fluid, a particularly tasty type is cream.  Cream goes from a liquid to a solid when you apply force by whipping it with a whisk.  We made a type of non-Newtonian fluid called an Oobleck, not nearly as tasty as whipped cream, but it sure is fun to play with!

Getting Messy!

We poured our Oobleck, we poked our Oobleck, we rolled our Oobleck into a ball.  It felt awfully funny.  Some words the students used to describe Oobleck were “slimy”, “squishy”, and “quicksand.”  Yes, quicksand is a type of non-Newtonian fluid!  It was also observed that if you stuck your finger into the Oobleck slowly it went in easily, as if you were placing it in a glass of water, but as soon as you moved your finger quickly it felt as though the Oobleck was eating it!

When you stop applying force to oobleck it flows like a liquid.

When you stop applying force to Oobleck it flows like a liquid.

There are plenty of other cool things you can do with Oobleck as we saw from these cool YouTube videos:

Can You Walk on Water?

Non-Newtonian Fluid on A Speaker

Exploring how Oobleck can be both a solid and a liquid.

Exploring how Oobleck can be both a solid and a liquid and creating some cool art in the process.

You should never, ever dump Oobleck down the drain as it could clog your pipes so it took us a little while to get all cleaned up.  Once we had clean hands and a clean working surface we were on to our next experiment… invisible ink.

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Many of the kids told me that they had made invisible ink before using lemon water ink and heat to develop the message, but now they have a new method to share along with some super secret code names.  With this experiment you can still use lemon juice as ink, but I find that baking soda mixed with equal parts water works as an even better ink.  Once your message has completely dried you can pass it on to a friend so they can develop it by lightly painting over the baking soda with grape juice.  (Note: Grape drink will not work)   This works because grape juice is an indicator, meaning it changes colour when exposed to either an acid, such as lemon juice, or a base, like baking soda.   This takes place through a chemical reaction.  Usually acids will turn the indicator red, where as bases will turn it green.  Neutrals, such as water, will result in no colour change.

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Our last experiment of the day was probably the least messy, but the most unlike anything the students had  seen before.  We discussed the difference between a conductor, which is usually some type of metal and allows electricity to easily pass through it, and an insulator, such as wood or rubber, that does not support an electrical current.  The students then saw a demonstration of a circuit.

We used a special type of dough that conducts electricity, LEDs, and AA battery packs to create our own squishy circuits.

Testing Out Squishy Circuits

Before we began we had to go over some very important safety rules.

3 volt battery packs such the ones we used are not dangerous and don’t hold enough of an electrical charge to hurt anyone.   You still should be cautious and avoid touching the bare red and black wires to each other, as this will overload the batteries.
You should also avoid hooking an LED directly up to the battery pack without some sort of resistor in between.  A resistor is anything that lessons the electrical charge, in this experiment the conductive dough acts as a resistor, lowering the charge enough that the electricity can flow through the LED without overloading the light and causing it to pop.

The idea of working with electricity was a little scary to begin with, but once the kids realised the dough wasn’t going to shock them they were able to explore with confidence.

circuits4We rolled our dough into two little sausage shaped pieces then placed them side-by-side with a small space between them.  Once that was complete we inserted the red (+) wire into the dough on the right and the black (-) wire into the dough on the left.  A coloured LED spanned the two dough balls, completing the circuit.

But some circuits didn’t work!  What was wrong?

In order to discern what was different between the circuits that worked and the circuits that didn’t, we had to analyse how our circuits worked under different conditions.   The first thing we checked was which way our LEDs were placed in our circuit.  Electricity flows in a very specific way, with electricity flowing from the positive side of the battery pack, through the red (+) wire, into the first dough ball, through the LED, out through the second dough ball and back into the black (-) wire and into the negative side of the battery pack.  Just like batteries, LEDs also have positive and negative sides.  You can tell which is which by observing the two wire leads on an LED, the longer side is the positive side and must be placed into the dough ball with the red wire.

Experimenting to find out why the LED isn't lighting up.

Experimenting to find out why the LED isn’t lighting up.

With all LEDs placed in their proper positions, there were still a few lights refusing to glow.  It was time for another test!  Students with working circuits were asked to push their two dough balls together to see what would happen… the unanimous response back was, “My LED went out!”

Electricity is incredibly lazy and it will always take the easiest route possible, when presented with the option to either travel through the dough or travel through the LED, it will always take the easier route of travelling through the dough.  This is called a short circuit.

Once everyone added a space between their two dough balls all the LEDs lit up!  Another way you can prevent your circuit from short circuiting is by adding insulator dough in between your two dough balls.  We did not explore this option in class, but the recipe cards the students were sent home with include this so you can try it out at home and create more advanced dough creations that light up.

If you are interested in delving more into how electricity works, check out this awesome video:

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