Sacrificial anode     Iron can be protected from rusting by commecting a more reactive metal (such as magnesium) to it. The magnesium reacts in preference to the iron and, if the magnesium is placed in an easily accessible location, it can be replaced more easily than the iron structure.

Salt     In general this is a compound formed when an acid reacts with a metal, a metal oxide, a metal hydroxide or a metal carbonate. You need to know these general equations:

METAL + ACID       goes to           SALT   +   HYDROGEN

METAL OXIDE  + ACID       goes to           SALT   +   WATER                      

      METAL CARBONATE  +   ACID       goes to           SALT   +   WATER   +   CARBON DIOXIDE

Hydrochloric acid gives chlorides
Sulfuric acid gives sulfates
Nitric acid gives nitrates

Common Salt has the chemical name sodium chloride. It is the salt that you might use to put on chips !

You could make common salt by reacting sodium hydroxide with just the right amount of hydrochloric acid. Be careful to use just the right amount though!

Sandstone     Grains of sand can be formed into this sedimentary rock by the processes of dposition and cementation.

Saturated    This has many different meanings depending on the context.

1.     Saturated solutions cannot dissolve any more solute at that temperature.

2.     Saturated hydrocarbons (alkanes) have only carbon and hydrogen atoms and use only single bonds.

Sediment     The grains of rock or animal remains that are dropped to the bottom of a river, lake or sea.

Sedimentary rock     Rock formed from layers of sediment after the grains of sediment have been squashed together and have  undergone cementation.

Shape memory alloys     These can be bent into a variety of shapes but will return to their original shape when heated. They can be used for medical applications where even the warmth of the body can cause a row of sutures made of them to pull a wound together.

Slaked lime     Calcium hydroxide, it is made by adding a limited amount of water to quicklime (calcium oxide). It can be used as a soil additive to reduce the acidity of soil.  

Smelting     The extraction of a metal from its ore.

Structural formula     This is sometimes called a displayed formula. It shows the arrangement of the atoms within a molecule. When drawing the structural formula for a hydrocarbon, remember that all carbon atoms must have four bonds and every hydrogen atom has only one bond.

Sulfur compounds     They are present in crude oil and so find their way into petrol and diesel. When they are burned, sulfur dioxide is released.

Sulfur dioxide     This gas is a major contributor to acid rain. It is formed by the combustion of sulfur and sulfur compounds. It is an irritant too.

Symbol (chemical symbol)     This may be one, two (or even three) letters. The first letter is always a capital. The others are lower case. The three letter symbols are for elements taht have not yet been assigned a name (eg ununquadium which is atomic number 114 and has the symbol Uuq).

Symbol equation     If a chemical equation is done using symbols it MUST be balanced. There must be the same number of each kind of atom on each side of the equation.



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