Elements and Compounds: A Concise Guide
Emulsions
Have you ever noticed the two layers of liquid in a bottle of salad dressing? What can you do to the bottle to mix the oil and water together? Oil floats on top of water. The liquids are immiscible. They only mix when you shake them up. Then the oil and water mix as tiny blobs. This type of mixture is called an emulsion.
What happens when you leave the emulsion to stand for a while? Salad cream is an emulsion. Does it separate out into two layers, like salad dressing? You don’t have to shake a bottle of salad cream to mix it. It has egg yolk added. This is an emulsifying agent. It stops the oil and water separating into layers. Many food additives are emulsifying agents. Just look on a bar of chocolate.
Foams
A foam is a mixture of a gas spread through a liquid or a solid. Can you think of any examples of solid foams? Why do we need special rules about the type of foam used in furniture?
Lithium
Lithium gets its name from the Greek word for stone. As the metal itself, we use it to strengthen other metals, such as magnesium, in alloys. It is also used in batteries. Lithium batteries are powerful and lightweight. In fact, you might be nearer than you think to a lithium battery now! They are suitable for calculators, watches, and cameras. They are also used in heart pacemakers.
Lithium Compounds
Lithium compounds have been used more and more since the Second World War.
- Medicine: Lithium carbonate is used to treat mental illness.
- Glass: Lithium carbonate is used in making tubes inside TVs and for lenses which darken in sunlight.
- Air Conditioning: Lithium carbonate is used in air conditioning systems and in submarines to remove carbon dioxide.
- Kill Germs: Lithium hypochlorite kills germs in swimming pools and in hospital laundries.
- Ceramics: Lithium oxide is added to ceramics, from ovenware to the nose cones of rockets.
- Dyes: Lithium hydroxide helps to dye nylon and paper.
Potassium Compounds
Potassium is essential for the healthy growth of plants. Potassium nitrate is used as a fertilizer. It is also used in making explosives and fireworks.
Sodium
The element sodium is used in street lamps and in nuclear reactors.
Sodium Compounds
Food Additives: Do you eat cereal for breakfast? If you do, have you ever read the box? You will almost certainly find some sodium compounds in the list of ingredients, even if it’s only salt. Common salt, sodium chloride, was the first food additive. Nowadays we use many other sodium compounds as additives. Sodium sulfite, sodium nitrite, and sodium nitrate are all preservatives. They stop bacteria growing. Other sodium compounds improve the texture of foods. But perhaps the most well-known additive is monosodium glutamate. It brings out the flavor in foods and is used a lot in Chinese restaurants. However, in some people, it can cause dizziness, headaches, nausea, and is dangerous to asthmatics. Not surprisingly, it is banned from baby foods!
Sodium Carbonate
The materials needed to make sodium carbonate are brine, limestone, and ammonia. We make about 26 million tonnes each year!
- Washing Powders and Liquids: It softens water.
- Sewage Treatment: It neutralizes acid.
Helium
If we cool down metals to very low temperatures, they lose their electrical resistance. They become perfect conductors or superconductors. Liquid helium is used to cool metals down. Helium boils at -269ºC! It is used to cool down the coils in body scanners in hospitals. The coils can then make the very strong magnetic fields that scanners need. These machines have become very important. This is very useful in finding cancers and helps doctors to judge what effect their treatment is having on tumors.
Have you ever seen an airship? Perhaps at a sporting event? Cameras on board provide those fantastic views looking down on the arena and crowds. As you know, helium is much less dense than air. It is used to fill airships to provide lift. However, the first large airships built in the 1920s used an even lighter gas – hydrogen. Can you think of any dangers using this gas?
Neon
Late in the 1800s, scientists were investigating gases and electricity. They found that a gas at low pressure can be made to glow if we apply a high voltage to it. These discharge tubes helped scientists like J.J. Thomson find out more about electrons and atoms. Nowadays we use the noble gases to make many of the brightly colored lights you see in cities. Neon is the gas used for red signs.
Argon
Light bulbs are filled with argon gas. Why do you think that air is replaced by argon? Argon won’t react with the tungsten metal filament inside the bulb, even when it is white-hot. Its lack of reactivity also helps in welding. It acts as a shield around the hot metal in the weld. What might happen otherwise? It is also used in the extraction of titanium metal. We also pump the gas into the molten mixture to stir it up when making steel.
Krypton
Krypton gas is in the lasers that doctors use to operate on eyes. The laser opposite is being used to repair the retina at the back of the eye.
Radon
There is hardly any radon gas in the air. But in some parts of the country, people have had to check the levels of this gas in their homes. In rocks, such as granite, there are small amounts of naturally occurring radium. This radioactive element breaks down into radon gas which is itself radioactive. So the gas can build up and become a danger to health. Some houses have pumps installed to make sure the air inside is changed regularly. Ironically, radon is used to help treat cancer.
Preventing Rust
Unfortunately, iron and steel rust. However, we have found some very effective ways to fight against rust. You have just read about alloy steels. If chromium and nickel are added to steel, you get stainless steel, a steel which does not rust. Stainless steel is expensive, but it is used for small items such as knives and forks. Why don’t we make cars from stainless steel?
Sacrificial Protection
Magnesium can be used instead of zinc. It is used in harsh conditions.
Common Laboratory Apparatus
- Test tube (tubo); test tube rack (soporte para tubos); Bunsen burner (mechero bunsen)
- Mortar and pestle (mortero); spatula (espátula); round-bottomed flask (matraz de bombilla): wire gauze (rejilla)
- Beaker (vaso de precipitados); digital scales (báscula digital); tripod (trípode); dropper (cuentagotas); filter funnel (embudo)
Elements
Aluminum (Al); Argon (Ar); Arsenic (As); Barium (Ba); Beryllium (Be); Boron (B); Bromine (Br); Caesium (Cs); Calcium (Ca); Carbon (C); Chlorine (Cl); Chromium (Cr); Cobalt (Co); Copper (Cu); Fluorine (F); Gallium (Ga); Germanium (Ge); Gold (Au); Helium (He); Hydrogen (H); Iodine (I); Iron (Fe); Krypton (Kr); Lead (Pb); Lithium (Li); Magnesium (Mg); Manganese (Mn); Mercury (Hg); Neon (Ne); Nickel (Ni); Nitrogen (N); Oxygen (O); Phosphorus (P); Platinum (Pt); Potassium (K); Rubidium (Rb); Scandium (Sc); Selenium (Se); Silicon (Si); Silver (Ag); Sodium (Na); Sulfur (S); Strontium (Sr); Tin (Sn); Titanium (Ti); Uranium (U); Vanadium (V); Xenon (Xe); Zinc (Zn)
Ode to Dmitri
The periodic table was a scientific breakthrough.
For chemistry made sense, it was easier too.
A Russian named Dmitri was first to spot the pattern,
But some elements were wrong in the spaces they sat in.
Some elements were as yet undiscovered,
So he made predictions from the properties of others.
A few years later when germanium was found,
Scientists agreed his ideas were sound.
Even now we use the table in which we never dine,
Still based on that discovery in 1869.
Dmitri Mendeleev was the youngest of 17 children!