Why Cookies Get Bigger in the Oven

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Simon is baking Dutch traditional “pepernootjes” (“pepper nuts” or spicy cookies) and explains why they get bigger in size after you put them in the oven and what the optimal tiling pattern is to fit a maximal number of cookies on the baking sheet.

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Sugar and Salt

Want some me sugar in your tea?

Simon built this sucrose (table sugar) molecule with the help of Theodore Gray’s Molecules book (although he is pretty sure there is a mistake in the Dutch version of the book, on a different page, where the fructose, glucose and galactose molecular structures seem to be mixed up – the sucrose description helped him discover this as the table sugar molecule is made up of one fructose and one glucose molecule).

Simon is also fascinated how sugar and salt, substances that are easy to confuse on the kitchen table, are made of molecules that are so “wildly different”:

Physics Experiments: Capillary Bowl

Simon really wanted to try building a capillary bowl – a version of a perpetual motion machine in which water circulates. Although aware of the fact that perpetual motion was not possible, he is keen on seeing it for himself. Off we were to the hardware store where we got some funnels and hoses. What we observed was Pascal’s law in action: the level of water evened out and there was no way to get the water rise higher at one end of the hose than at the other and thus no way to get the water flow into the funnel.

Eventually, we did manage to get the capillary bowl to work for a split second when we filled it with coke and beer. The pressure of water is higher than that of foam, because liquid has a higher density than foam. We used alcohol free beer, so there wasn’t that much foam.

Physics Experiments: Slime for Science

We had such a genuinely rewarding homeschooling experience yesterday when we took up Physics Girl’s challenge to recreate the Weissenberg effect – a phenomenon that occurs when a spinning rod is inserted into a solution of elastic (non-newtonian) liquid.

Our first attempts to make slime following Physics Girl’s recipe (1/2 cup PVA glue, 1/2 water plus 1/4 tsp borax dissolved in another 1/2 warm water) failed so we returned to the department store to get starch, a different type of glue and anything else that might help. Did we use the wrong glue? What is borax (originally, we thought it was the same as the salt used to clean the dishwasher)?

After we started asking around, the shop assistants threw in a couple of handy tips (like getting some fluid used for cleaning your contact lenses as it contains something like borax, borate buffers, and mixing that with glue and shaving cream). At the drug store, we got warned about the dangers of pure borax powder if used in large quantities (skin burns), but did manage to get a tiny bottle of the stuff after we assured that it was for an adult supervised experiment. With all this useful info and terribly tired, but fully equipped we returned home and resumed our attempts at mixing perfect slime. You can see for yourself in this unlisted video how we went about it.

Eventually, we ended up adding twice (in not thrice) the amount of borax to finally froth up the right consistency non-newtonian fluid and it just worked!

(Instead of being thrown outward, the solution is drawn towards the rod and rises up around it. This is a direct consequence of the normal stress that acts like a hoop stress around the rod).

Simon wrote: In this video, I make slime “climb” up! It’s because of the “viscoelasticity” of the slime.

Correction: I’ve made a mistake when I said “times H2O”. The dot in the formula didn’t mean “times”, it meant ion.

The borax formula was indeed what Simon called “a mouthful”: Na2[B4O5(OH)4]·8H2O where the dot refers to the elements in square brackets all forming the [B4O5(OH)4]2− ion.

So what is borax? It’s a mineral, a salt of boric acid, also called (di)sodium tertaborate, usually possessing a crystal water content (although the commercially available borax is partially dehydrated).

Thanks to more borax, check out how high our fluid rose – it came out the other side of the straw!

Building dinos and looking them up in the encyclopedia

Although Simon doesn’t have the Magformers Dinosaur Set, he does have all the pieces (he collects the set using the pieces from other sets). It’s great fun to be able to look up the dinos and the instructions in the Magformers online pdf books and bring them back to life:

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We also read up on how these dinos lived in the encyclopaedias.

Physics Experiments: How to build a simple generator

Simon came up with the idea to make this simple electric generator a while ago, but we had bad luck with the ceramic magnets we ordered: they had chipped ends and literally crumbled in my hands, which I found very dangerous. Simon was extremely upset when I told him we couldn’t use those magnets and had to order new ones, not ceramic but neodymium ones this time. Even though we had to wait for the new set of magnets, Simon had already prepared the square cardboard base with the long iron screw piercing it in the middle. He made it all by himself. Today we finally had the time and everything necessary for the project:

a 1,5 Volt, 40 mili-ampere miniature lamp;

coated copper wire,  0,25 mm thick;

and of course, two new 40 x 20 x 10 mm neodymium magnets (very strong, make sure to take precaution as such magnets can cause injuries when they jump towards each other — adult supervision required).

The generator works because of Faraday’s law, which states that a dynamic (moving) magnetic field creates electricity. The objective is to make sure the magnets can freely spin inside your cardboard box when you turn the iron screw. We put around 250 loops of copper wire around the box to create a coil (Simon actually counted). Carefully scrape the enamel off at the tips of the two loose ends of your copper wire and attach those to the lamp’s contacts.

Physics Experiments: The Color Wheel and Mind Blending

Inspired by Physics Girl, here come a couple crafty color wheel experiments involving what Physics Girl calls “mind blending” (it may not be the real name) – mixing color wave lengths in your mind. Simon has already studied the way our brain perceives blended/ moving color before, in the several optical illusions he programmed. This time, however, he decided to observe how simple paint can produce the same effect.

CORRECTION by Simon: You can’t actually even see the entire visible spectrum. You only see red, green and blue (I couldn’t think of that in the video).

The rotating green and red disk look more yellow in this extra 2 sec of footage taken by a different camera:

Simon prepared the props himself, with some help from his sister New (who painted one of the disks) and me (I helped cutting the hard cardboard). We couldn’t figure out a way to get the disks to spin fast and tried several options (like straws, pencils and even a dismantles giroscope). Eventually, we decided to use a small drill from a children’s woodworking set and it worked!

Making the fourth disk was the most difficult part as Simon wanted to divide the circle into 12 equal sectors. He came up with this elegant solution: he drew a hexagon and then bisected every angle (see below).

Simon made his own foam Rubik’s Cube

Simon saw this design in a video by Mathologer and adapted it slightly (Mathologer used glue and no screws). He had dreamt of making a cube like this for months, but the idea of crafting one from wood seemed too complicated. Today it occurred to him that he can make the design using his new woodlike foam and press iron screws into the foam to hold the magnets! On to the wooden model now!