Why do we crave chocolate, and what happens to aeroplane toilet waste?

Why do we crave chocolate?

Chocolate contains large amounts of phenylethylamine, which is also present in our bodies and released during sexual arousal, heightening sensation and raising the heart rate. It also contains methylxanthine and theobromine, which have similar effects to caffeine. And if that isn’t enough, it is solid at room temperature but melts at just below body temperature – that is, in your mouth.

Why don’t the chocolate chips in cookies melt during cooking?

To all intents and purposes, they do, but they are held in place by the dough around them. However, the chocolate doesn’t melt as much as ordinary chocolate because it has been tempered. Tempering is when chocolate is repeatedly heated and cooled until a crystal-like structure appears within it. This makes the chocolate more stable and gives it a glossy shine and a crispy surface.

Why is it dangerous to burn many fuels in a limited air supply?

Insufficient air means alkanes and other carbon-based fuels burn to give carbon monoxide and carbon (soot) instead of carbon dioxide. This is called incomplete combustion.

Carbon monoxide is poisonous and responsible for many accidental deaths.

Gas fires that haven’t been serviced regularly can burn gas incompletely. In a poorly ventilated room, the build-up of carbon monoxide can put the occupants into a coma and kill them if they are not found.

Carbon monoxide detectors are available, which, like smoke detectors, sound a blaring alarm.

Why does electricity like to go to earth?

The flow of electricity is a result of what is known as a potential difference. This is like a pressure difference in a water pipe. If you fix a hosepipe to a tap and turn the water on, the water flows because water pressure at the tap forces the water through the pipe – but if the hose end is closed, it won’t flow. Electricity is the same. Electrons at one end of the wire have energy, while those at the other end connected to earth haven’t. This creates an “energy pressure” that forces the energy along the wire. Of course, for the purposes of an electrical circuit, earth can be defined as a point in the system with a lower potential than any other. The electrons then flow to that.

Why do blades in razors, which are many times harder than the materials they are designed to cut, become blunt?

The fact that steel is much stronger than hair is largely irrelevant; water is much “softer” than rock, yet most of the Earth’s surface has been moulded by the action of water. A blade is thin. The thinner the blade and the more regular the edge, the sharper the cut and the more often it has to be sharpened to maintain that sharpness. As the blade passes over the stubble on a person’s chin, the hair knocks off individual atoms from the edge of the steel blade. As there are many thousands of hairs, it doesn’t take long to dull the blade slightly. When we consider a blade to be dull, it has not really lost that much of its edge. Even if each hair only removes one atom, the blade can be dulled quickly.

Why does it always take longer to fly from east to west than from west to east?

Because of the wind. Winds in the upper atmosphere always flow from west to east. If you are flying from east to west, you have to fly against the prevailing wind, which means the journey takes longer.

What happens to waste from aeroplane toilets?

It’s a myth that it can leak out and fall to the ground in huge frozen blocks. Waste on aircraft is stored in tanks, which are pumped out later on the ground. The bits of ice that can fall from a plane generally come from the wings, where ice accumulates from water vapour in the clouds.