Science Ace 2 (Post 3)

This blog posting is going to be on using science to do magic.

The trick is called the "burning" note trick.

This is a good 'magic trick' that illustrates the process of combustion, the flammability of alcohol, and the special qualities of the material used to make currency.

A combustion reaction occurs between alcohol and oxygen, producing heat and light (energy) and carbon dioxide and water.

When the bill is soaked an alcohol-water solution, the alcohol has a high vapor pressure and is mainly on the outside of the material (a bill is more like fabric than paper, which is nice, if you've ever accidentally washed one). When the bill is lit, the alcohol is what actually burns.

The temperature at which the alcohol burns is not high enough to evaporate the water, which has a high specific heat, so the bill remains wet and isn't able to catch fire on its own. After the alcohol has burned, the flame goes out, leaving a slightly damp dollar bill.

Science ACE (Post 2)

Why does ice float on water?

According to actual facts, solids are heavier than liquids. So, why does ice(a solid) floats on water(a liquid).

Firstly, let me explain why anything floats in the first place. Something that floats is always less dense than whatever it is floating on. Density is measured as mass over volume.

Let me give an example. A iron coin sinks to the bottom of the ocean because a iron coin is more dense than the ocean. Iron has a density of 7874 kg/m-3 while sea water has a density of 1025 kg/m-3. That is because iron has a bigger mass than sea water, so when a bigger mass is divided by a smaller volume, that results in a bigger density.

Now that you know what is density, let me answer the question.

Ice can float on water because a certain mass of ice occupies more space than the same mass of water. A water molecule is composed of two hydrogen atoms and one oxygen atom. The atoms of hydrogen and oxygen are bound by sharing their electrons with one another. This bond is called a “covalent bond”.

However, since oxygen atoms pull electrons more strongly than hydrogen atoms, the oxygen atom in a water molecule has a slightly negative charge and the hydrogen atoms have a slightly positive charge.

Therefore adjacent water molecules are attracted to one another through the slightly negatively charged oxygen atoms and the slightly positively charged hydrogen atoms. This interaction is called “hydrogen bonding”. Hydrogen bonding is much weaker than covalent bonding, however, this type of bonding has a large total effect because there are so many hydrogen bonds.



The conclusion is that there is more space in ice than water, therefore ice can float on water!

-ice

-water