Tutor profile: Laura C.

Why can't we divide a number by 0?

When you divide eg. 10/2 we are asking: how many 2's do we need to get 10? We know the answer is 5. Let's think now about 10/0-- well, how many 0's do we need to get 10? Silence.....there is no answer. It just can't happen.

Why are diamonds so hard?

In chemistry we have a few types of bonds: ionic bonds, hydrogen bonds, covalent bonds. Hydrogen bonds can be found for example in water, and they are very easy to separate during boiling. Hydrogen bonds are considered the weakest bonds. Next in strength come the ionic bonds- bonds formed by the attraction of two oppositely charged ions which usually form crystals such as salt. As we know salt crystals don't break or disappear easily unless dissolved in water. The strongest type of bond is the covalent bond, in which atoms share electrons so their bond is very tight and almost unbreakable. If one covalent bond is hard to break, imagine that a carbon atom can form 5 covalent bonds with other carbon atoms. This carbon lattice form is what makes a diamond.

What are epigenetic changes?

You can think of epigenetic changes as small markers that attach themselves to the DNA sequences in our body. Once attached, they can either activate or deactivate the gene they are attached to-- changing the gene expression. The result is that even though genetically someone's gene for eg. a certain disease is switched off and doesn't manifest, an epigenetic change could activate it and now, unfortunately, you have the disease. This epigenetic changes are not related to illnesses only, but they can also change our skin/hair colour and usually occur because of environmental factors, diet, age etc. Some epigenetic changes can also be inherited, so the same environmental effect can be transmitted from generation to generation. An interesting example is that the children/grandchildren of people who lived in famine are more likely to be obese-- a gene for energy preservation is probably switched on forever.