Frequently Asked Questions: Elements and Compounds

Q. There are two forms of oxygen - oxygen gas that we breathe and ozone, a poisonous gas. What are the formulae for these two forms?
A. Oxygen = O2, Ozone = O3

Q. The Bible mentions 'fire and brimstone'. What element is brimstone?
A. Sulphur

Q. Why is the element Helium incorrectly named?
A. Elements with the suffix 'ium' are metals e.g. aluminium and uranium. Helium is a gaseous non-metal.

Q. If diamond and graphite are both forms of pure carbon, why are they so different in properties?
A. The carbon atoms in graphite are in layers and so it is softer and more easily rubbed off onto paper as we write. The carbon atoms in diamond are in a strong three-dimensional network which makes diamond much harder.

Q. Why do rotten eggs smell rotten sometimes, and why do they sometimes have a slightly green-looking yolk?
A. Rotten eggs smell strongly of hydrogen sulphide, often called rotten egg gas. This gas is released from the sulphur-containing proteins in the white of the egg. This gas can react with iron in the yolk to make a greenish chemical called iron sulphide.

Q. Why are fireworks colourful?
A. Fireworks contain different salts. When salts containing different metal ions are burnt, each produces a different colour. The heat excites the outer electrons of the metal and they release different colours of light as the electrons fall back to their original state. For example, sodium ions produce a yellow flame, copper ions produce a green flame and potassium produces a mauve flame.

Q. What are the scientific names for common salt, chalk, table sugar and vinegar?
A. Sodium chloride, calcium carbonate, sucrose, acetic acid

Q. What common substances have these formulae - H2O, CO2, NaCl and C12H22O11?
A. Water, carbon dioxide, common salt, table sugar

Q. Is glass a liquid or a solid?
A. Glass is a super-cooled liquid.

Q. What artificial sweetener was accidentally discovered in 1879 by a scientist who had his cup of coffee next to his experiment?
A. Saccharin

Q. A mole is both a partially blind animal and a number of atoms. How many atoms are in a mole?
A. 6.02 X 10 23 atoms are in a mole (that is 602 000 000 000 000 000 000 000 atoms).