Derek Shirlaw

Derek Shirlaw | Chemistry | Atoms

The smallest particle that still characterises an element.

Let's think about the physical building blocks of everything in the Universe.

Particles of matter - Atoms - Elements - Molecules - Macromolecules - Cell organelles - Cells - Tissues - Organs - Systems - Organisms - Populations - Ecosystems - Biospheres - Planets - Planetary Systems with Stars - Galaxies - The Universe

Atoms are complex associations of many particles of matter.

Derek Shirlaw | Chemistry | Carbon

Carbon: The 4th most abundant element in the Universe after Hydrogen, Helium and Oxygen. It is found in abundance in the Sun, stars, comets, and atmospheres of most planets. The atmosphere of Mars, for example, contains 96% CO2. It is the chemical basis for all known life and is found in many different compounds. It is in the food you eat, the clothes you wear, the cosmetics you use and the petrol that fuels your car.

A Group 14 element, Carbon is found free in nature in three allotropic forms: amorphous (irregularly shaped), graphite, and diamond. The differences in their structure are profound. Diamond crystalises in a cubic system, whereas graphite does so in a hexagonal, layered system. As a result, graphite is one of the softest known materials while diamond is one of the hardest.

Carbon, as microscopic diamonds, is found in some meteorites. Natural diamonds are found in ancient volcanic "pipes" such as found in South Africa.

More recently, another form of carbon, buckminsterfullerene, C60, has been discovered. This new form of carbon is the subject of great interest in research laboratories today.

Carbon is present as carbon dioxide in the atmosphere and dissolved in all natural waters. It is a component of rocks as carbonates of calcium (limestone), magnesium, and iron. Coal, petroleum, and natural gas are chiefly hydrocarbons. Carbon is unique among the elements in the vast number of variety of compounds it can form.

Derek Shirlaw | Chemistry | Acids and Alkalis

Acids are chemical compounds that when dissolved in water, create a solution with hydrogen ion activity greater than in pure water; less than pH7. Alkalis are an ionic salt of an alkali metal that dissolve to give a pH greater than 7.

As the most common molecule in the universe, water (H2O) is made up of one atom of oxygen and two atoms of hydrogen.

Water molecules are polarised, meaning that the oxygen atom pulls on the hydrogen atoms leaving them with a more positive charge, whilst the oxygen becomes more negative. This polarity allows water to easily dissolve other polarised molecules into ions. Water itself is constantly dissociating into H+(hydrogen or 'proton') and OH- (hydroxide) ions.

Acids are compounds which donate hydrogen ions in solution, free-ing up hydrogen gas as they attack metals.

Alkalis (or bases) are compounds that accept hydrogen ions and include such compounds as metal oxides, hyrdoxides and amines.

Alkalis and acids combine to form a salt and water.

For example:
HCl + NaOH = NaCl + H2O
Hydrochloric acid + Sodium hydroxide = Sodium chloride (common salt) + Water

Derek Shirlaw | Chesmitry | Solid, Liquid, Gas & Plasma

The most commonly referred to states of matter are solid, liquid, gas and plasma.

These 'phases' or 'states' see solids with closely-packed atoms in rigid arrangements.

Heating these atoms provides energy that allows them to vibrate and shake apart, forming liquids that can flow and adopt shape.

Continuing to heat these atoms loosens bonding further and allows atoms to spread out at great speed in all directions as a gas.

At greater temperatures still, electrons can be knocked out of the atoms grasp to form an electrically charged, ionised plasma, the effects of which you can see in 'plasma balls' or in pictures of the corona of the Sun.