Chemistry Terms.

L 

• LIME STONE

Limestone rocks are sedimentary rocks that are made from the mineral calcite (Calcium carbonate) often used as building blocks.  This is the raw material for  quick lime and cement.

M  

• MARBLE

Hard crystalline shiny rock consisting of  of carbonates of Calcium ( Ca CO₃)and magnesium (MgCO₃).  Taj Mahal in India is almost entirely marble.

• METALS

Majority of the elements

in the Periodic Table are metals.

Fig. Periodic Table The periodic Table shows all the elements. Out of that except the red, blue and the halogens in between all the others are metals.

They all have the following general properties.

1. Usually high dense except alkali metals.
2. A clean surface will have a shine.
3. All are solids except mercury Hg which is a liquid.
4. All have a silvery colour except gold and copper.
5. Good conductors of heat and electricity.
6. Form positive ions by lending electrons.
7. Shows an affinity for non metals.
8. Some metals react with Dil. Hydrochloric acid yielding hydrogen.

• METHANOL

CH₃OH  is the simplest member of the homologous series of alcohols. This is also known as methyl alcohol  and used chiefly as a solvent, a fuel, and an automobile antifreeze

• MIXTURES

We may say , “All mixtures are not pure substances” but the word ‘pure’ does not have a clear meaning. Drinking water or country air may be considered as ‘pure’ but they will contain impurities. Even the cleanest water will contain dissolved gases and salts. Air is a mixture of Nitrogen, Oxygen, Argon and water vapour with various suspended particles.

Even supposed to be pure coconut oil or kerosene oil are not pure but mixtures of similar compounds. ( Compounds are not mixtures)

The ingredients of a mixture can generally be separated by physical methods whereas the elements in a compound can only be separated by chemical methods..

        Homogenous  Mixtures 

The composition of ingredients in a homogenous mixture will be the same in two or mare samples taken.

    Eg : -  All true solutions,  Air, clear tap water, sea water , blood , brass (an alloy of zinc and copper)  18 carat gold are examples. Ingredients cannot be separately seen even through a microscope.

        Heterogeneous mixtures

Often the separate substances can be seen with the naked eye or through a microscope. Eg :- Soil, mortar, muddy water, rocks, cloud

Dispersed solid or liquid particles are so small and cannot be seen separately. If a beam of light is passed through the medium the light will scatter.  When a colloid is formed by two liquids, oil and water, it would be an emulsion.

• MOLECULE

This is a group of  two  or more  atoms chemically bonded together to form a pure substance.  Atoms  may be of the same kind as in di atomic gases. A molecule of oxygen has two atoms of the same kind.

Eg.  Oxygen O₂,     Carbon dioxide  CO₂,  Water  H₂O  ,  Glucose  C₆ H₁₂O ₆

• MOLAR SOLUTIONS

 A solution that contains a definite number of moles  of solute dissolved  in 1 litre (dm3) of the solution.  The molarity is denoted as  1M., 2M, 0.5 M.  etc., 

• MOLE

Molecular  weight of a pure  chemical, taken in grams  consists of one mole (mol) of molecules

1 mol of any chemical substance will give the same number of molecules  which is equal to the Avagadoro number. This denoted by the symbol … N_A.

N_A.  =  6.02 x 10 ²³        particles

N

• NEUTRALIZATION

Usually this refers to an acid becoming neutral by the addition of a base.

Eg 1.:-    HCl  +  NaOH    →    Na Cl   + H₂O

            1 mol + 1mol        →      1 mol   +  1 mol

Eg 2:-   H₂SO₄  +  2 NaOH   →      Na₂ S O₄  +  2 H₂O

            1 mol +        2mol        →      1 mol  + 2 mol

Acids may also be neutralized by carbonates and the metals above H in the activity series.

Eg 3:-    2 HNO₃  + CaCO₃    →       Ca (NO₃)₂ +   H₂ O + CO₂

Eg 4 :-  2 HCl   +  Zn    →   ZnCl₂   +  H₂

• NITROGEN

i.   The element

The atmosphere contains nearly 79% of Nitrogen  20% of oxygen  excluding water vapour and suspended dust etc, . Although the gas is quite stable under normal conditions, during lightening, it combines with Oxygen to form oxides. NO₂, N₂O₄, and NO. 

This is mainly used to manufacture ammonia which is necessary to make fertilisers. These fertilisers get bound to the soil and the  effect of getting washed away is at a minimum.

ii.  Nitrogen cycle

Nitrogen is an essential element for organisms. Yet it cannot be taken in directly. Nitrogen is present in the soil as nitrates .  KNO₃ , NaNO₃ and  Ca(NO3)_2, NH₄NO₃ etc,. These are absorbed as aqueous solutions by the plants to build body tissue. Animals get this from plants. When the animals and plants die Nitrogen is returned to the soil as nitrates. This is known as the Nitrogen cycle.

• Periodic Table

This is an arrangement of all the elements into groups and periods according to Atomic numbers.