Limestone rocks are sedimentary rocks that are made 

LIME STONEfrom the mineral calcite (Calcium carbonate) often used as building blocks.  This is the raw material for  quick lime and cement.

• 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.

Go to Periodic Table .

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.

• MIXTURES

What is not a pure substance, That means a substance consisting of more than one kind of molecules or atoms is considered as a mixture. ( A pure element can have different Isotopes)

There are different types of mixtures.

       1.       Homogeneous  Mixtures 

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

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

       2.         Heterogeneous mixtures

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

          3.         Collids

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.

For more click  Pure substances and Mixtures .

• 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  

• 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

• 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.

•            OXIDATION

When an element combines with oxygen or chlorine or any other electro negative substance, the element is considered to have got oxidised. 

             Lending of electrons by an atom or an ion is also oxidation.   

             eg.  C + O₂ = CO₂   

• Opposite word -  Reduction.

• REDUCTION

        Removal of oxygen from a compound or combining with hydrogen.

        Gaining of electrons is also reduction.

• SUSPENSION
• A suspension is a heterogenous mixture where
   solid particles are dispersed in a solid, liquid or a gas medium.
  Particles can be separated by sedimentation or filtering.

• TYNDALL EFFECT  
  While a light beem can pass through a solution without being seen, a colloid will scatter the light, making the beem visible.