Unbreakable Prince Rupert’s Drops

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I came across these awesome glass drops in a video by Destin Sandlin from Smarter Every Day.

When you drop a piece of molten glass into cold water, the result is a tadpole shaped piece of extremely hard glass.

Three Prince Albert drops
Prince Rupert’s drops

Well, at least the head of the drop is very strong. The tail is actually quite delicate.

A shattering Prince Albert drop
A shattering Prince Rupert’s drop

The reason Prince Rupert’s Drops are so strong is that the outer layer of glass hardens almost straight away, while the inside takes a bit longer. When hot glass cools down (and this happens with water turning into ice too), the glass shrinks. This means that the inside of the glass drop is cooling down and shrinking but the outside is already cold and hard so the glass pulls towards the centre of the drop and makes it really, really strong inside.

Before we look at a really cool video of Destin from Smarter Every Day trying to break one of these drops using a bullet, take a look at his video that shows you how the drop is formed.

Right, now you have seen how the drop is formed and that hitting it on the head with a hammer won’t break it but if you nip the tail then the whole thing explodes.

Destin takes it a step further and shows us that even a speeding bullet won’t actually break the head of the drop itself.

Tip: try watch this on a large, high resolution screen for an even better experience.

How cool was that?!

Will a bowling ball fall faster than a feather?

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If you dropped a feather and a bowling ball at the same time, which would hit the ground first? You would probably say that the bowling ball would hit the ground first, right? After all, a bowling ball is so much heavier.

It turns out that the relative weight of the objects doesn’t make a difference to which object will hit the ground first, as strange as that may sound.

One of the parents in our class chat group shared this terrific video from the BBC that explains what really makes a difference and, surprisingly, that a bowling ball and a feather will hit the ground at the same time under the right conditions:

So, as you can see, the factor that makes the difference in normal conditions isn’t the objects’ weight, it’s air resistance! When you remove the air, both objects fall at the same rate and hit the ground at the same time.

Image credit: Pixabay

Marshmallows in a vacuum

Marshmellows
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Hi everyone, its the mom here, with my first Stuff to Teach Our Kids post.

I really like baking, the kids like mixing and licking the bowl. I also like teaching them how and why we mix the ingredients together and the reactions that take place when certain things mix. Baking really is just science. So I went looking for some fun baking experiments we could try.

I came across this video by The Crazy Russian Hacker about what happens to marshmallows in a vacuum. It looks like a really fun experiment to try at home and you can find a vacuum box like the one he uses on Amazon here. You can also make your own vacuum box using a wine bottle and a wine saver pump/stopper (instructions here).

According to Physics.org the science behind the growing marshmallows is as follows:

Marshmallows have small bubbles of air trapped inside them. These bubbles are at atmospheric pressure. When the air inside the glass container is sucked out, the volume of the container remains the same although there is much less air inside – so the pressure is reduced. The air bubbles inside the marshmallows are therefore at a much higher pressure than the air surrounding the marshmallows, so those bubbles push outwards, causing the marshmallows to expand. When air is let back into the glass container, the surrounding pressure increases again, and the marshmallows deflate back to their normal size.

As soon as we get the vacuum boxes we are going to try this out for ourselves and I will post a video of our results. Please let us know if you try it out too.

Image credit: Marshmellows by Maryam Abdulghaffar, licensed CC BY 2.0