The sting of a nettle – Laxmi Patel

It is not that hard to miss nettles. This plant’s growth can vary between 0.6 to 2 metres plus in height and can be found in a variety of habitats and soil types. The nettles prefer rich soils; therefore will grow well around human settlement (due to the waste humans produce).

The Latin name of the plant is dioica, which means ‘two houses’; this refers to the fact that the male and female flowers are normally carried on separate plants.

What is in the sting?

The structure of the nettle is very similar to a hypodermic needle. The sting is a hollow hair that is stiffened by silica with a swollen base that contains the venom. The tip of the hair is very brittle and when it is brushed against, it breaks off exposing a sharp point that penetrates the skin and delivers its stinging payload!

Formerly, it was thought that the main constituent of the sting was just formic acid (also known as methanoic acid), however recent research shows that there are other materials in the sting including: histamine, acetylcholine, 5-hydroxytryptamine (serotonin) and the last has yet to be discovered.

As it is known that the remedy is often found near the sting: dock leaves have been known to neutralise the sting and cool the skin down.

How the dock leaves work?

As dock leaves are a type of weed, the sap of a dock leaf contains a mixture of natural amines and natural histamines, this will help to decrease any inflammation. The amines are solvated and, as the sap is water-based, are alkaline. The alkalinity of the leaves means that the amines will react with the methanoic acid to produce a natural salt.

Bibliography:

CONE (date unknown) The Nettle – Urtica dioica. Available at: http://www.nettles.org.uk/nettles/lore.asp  (accessed at: 27/03/13)

Monk, P. (2004) Physical Chemistry: Understanding our Chemical World. Chichester: John Wiley

Flames? – Laxmi Patel

The Oxford Dictionaries describes a flame as: “a hot glowing body of ignited gas that is generated by something on fire”.

Fire is a visible effect of combustion, between oxygen, fuel, and energy.

 

The colour of the flame depends on the amount of oxygen available, for instance a blue flame is a product of high oxygen levels, whereas the orange/yellow flame is due to low levels of oxygen. But the reason for the yellow colour is that there is a glow of the unburnt carbon molecules. An example where you can prove this is in the science labs, using a Bunsen burner. You can experiment with the air hole and see how the flame changes from blue to yellow and vice versa. Blue flames typically means complete combustion.

There are three distinctive parts of the candle flame:

• Non-luminous zone (zone of complete combustion) = this is the hottest part of the flame, because of the adequate supply oxygen, there is complete combustion here. Hence, no residue is left, the flame may appear blue.
• Luminous zone (zone of incomplete combustion) = this part is moderately hot and due to inadequate supplies of oxygen there are wax vapours leftover. This will leave black soot and other residues when an object is placed here. An example of this is when you place your finger over a flame and then there will be a black mark. The orange glow is from the carbon molecules.
• Dark zone (zone of no combustion) = this is the least hot area of the candle. This is the area surrounding the wick containing unburnt vapours produced by the melting wax. The wax vapours do not come into contact with oxygen, therefore does not burn.

There is a small region at the base of the wick, here is where the carbon monoxide burns (blue colour).

A few sciencey terms:

• Pyrolysis – first, fuel turns to gas e.g. hydrogen and oxygen locked solidly forming wick.
• Chemiluminescence – atoms shine light when they rearrange = blue light/flame.
• Oxidation – oxygen combines with other atoms, makes the flame hot, due to the movement.
• Incandescence – not enough oxygen in the reaction so there is carbon left over = soot and it will burn brightly to make the flame yellow.

Here is an animation that I found that helps to explain what a flame is in a more visual way!

References:

http://oxforddictionaries.com/definition/english/flame (no date) accessed at: 05/03/13

The University of Waikato (2009) What is Fire? Available at: http://www.sciencelearn.org.nz/Contexts/Fire/Science-Ideas-and-Concepts/What-is-fire accessed at: 05/03/13