Calcium carbonate Limestone quarries:

 

Calcium carbonate

Have you ever seen the 'white cliffs of Dover?

If you have, you've seen lots of calcium carbonate.

Chalk is one form of limestone, made from around

98% calcium carbonate.

You might also find other rocks containing calcium carbonate

around your school

Limestone itself is a common building material. It might

be spread on the school roads or roofs as chippings.

Chalk is one form of limestone, made from around 98% calcium carbonate.

The chemical formula of calcium carbonate is CaCO₃.

Another source of calcium carbonate is marble.

Another source of calcium carbonate is marble.

The chemical formula of calcium carbonate is CaCO₃.

Many rocks with calcium carbonate in them were formed from

the shells of sea creatures that died millions of years ago. The

sediments built up on the seabed and slowly formed limestone.

Marble is formed from limestone crushed by powerful movements

in the Earth's crust and/or by very high temperatures near molten

rock (magma) underground.

Limestone quarries:

The pot-holing or caves have been weathered out of the limestone by rain water. Rain water is slightly acidic because carbon dioxide dissolves in it as it falls.

Have you ever visited the Peak District or the

Yorkshire Dales? If you have, you will have

enjoyed the beautiful views from the limestone hills.

You might have been pot-holing or visited the caves there.

These caves have been weathered out of the limestone

by rainwater. Rainwater is slightly acidic because

carbon dioxide dissolves in it as it falls.

You can see how limestone reacts with acid on page 204.

Limestone is a common rock in Britain. It is blasted

from the hillsides in huge quarries.

Look at the photo opposite:

Why do you think that many people are against?

any plans for new quarries?

these arguments have to be balanced against the benefits.

Limestone is a vital raw material for industry.

Look at its uses on pages 112 and 113.

New jobs and money are created for the area.

 Uses of limestone:

Cement

Have you ever watched brick-layers at work? They use

a mixture of cement and sand, with water added to make a thick paste. This is called mortar. It takes a lot of skill to set the bricks in the right position. What do you think would happen if their mortar was too runny? What if it was too dry?

Cement is made by heating limestone and clay (or shale). They are ground up and heated in kilns which rotate. A little gypsum (calcium sulfate) is added. This stops the cement from setting as soon as you add water.

Cement sets as it reacts with water. This is called hydration. The reactions are complex. We can think of it as fingers' of crystals growing out from each grain of cement. These interlock and bind the mixture together Mortar will set overnight. However, it carries on reacting and getting stronger for several months.

 

A mixture of cement and sand, with water added to make a thick paste. This is called mortar.

Cement is made by heating limestone and clay. They are ground up and heated in kilns which rotate. A little gypsum(calcium sulphate) is added. This stops the cement from setting as soon as you add water.

Cements sets as it reacts with water. This is called Hydration. The reactions are complex.

Concrete

What are the paths around your school made from?

Some will be made from concrete.

Concrete is made by mixing cement, sand and small stones.

If you look closely, you will see the small stones set in position.

Concrete is the most widely used building material

in the world. That explains why we produce about

1000 million tons of cement in the world every year

Concrete is made by mixing cement, sand and small stones. If we look closely, we will see the small stones set in position.

 

Reinforced concrete

Concrete is a relatively cheap building material.

As a material itself it is hard, but a beam will

snap if put under tension.

We can make it stronger by making reinforced concrete.

To make reinforced concrete, the mixture is allowed

to set around a steel support. Its increased strength

and flexibility means that we can use it to make

buildings and bridges. You've probably seen lots of

concrete on motorway bridges. The bridges would not

be able to span across gaps without the embedded

steel.

However, corrosion of the steel inside the concrete

Can be a serious problem, weakening a structure.

Reinforced concrete:

Concrete is a relatively cheap building material. As a material itself it is hard, but a beam will snap if put under tension.

We can make it stronger by making reinforced concrete.

To make reinforced concrete, the mixture is allowed to set around a steel support. Its increased strength and flexibility means that we can use it to make building and bridges.

Reinforced concrete composite:

Some of the latest research uses pulp from wood, plants and recycled paper.

The materials are shredded and sliced into small pieces before adding them to the concrete mixture. We call these reinforced concrete composites.

 Glass:

Limestone is one of the materials that we use to make glass. Glass is a strange material. Some people call glass the 4^th state of matter. it’s like a ‘solid liquid’.

Raw material:

i-  sand (SiO₂)

ii- limestone (CaCO₃)

iii- sodium carbonate-soda (Na₂CO₃)

Sodium carbonate is another useful product made from salt.

Re-cycled glass (cullet) is becoming more important. It can make up to  30% of some glass-making mixtures.

Different types of glass:

There are many different types of glass. Scientists have tried changing the glass-making mixture. They have also found ways of treating the glass to change its properties.

Example: Windscreens are usually made like a glass sandwich-with a thin sheet of plastic as the filling. This is called laminated glass.

Coloured glass

Have you taken any glass to be recycled at a bottle-bank?

The bottles are sorted out into different colours.

What are the most common colours of glass bottles?

Green and brown bottles get their colour from iron impurities in the

sand that it is made from.

                   Class Assessment

1. Mixture of cement and sand, with water added to make a thick paste is called----------.

a. mortar

b. Hydroxide

c. washing powder

2. Cement is made by heating limestone and------------------.

a. clay

b. Hydroxide

c. washing powder 

3. Cement sets as it reacts with---------------------. This is called hydration.

a. water

b. acid

c. base

                   Class Assessment

1. Chalk is one form of --------------------

a. Limestone

b. Hydroxide

c. washing powder

2. Chalk is one form of limestone, made from around------------- calcium carbonate.

    a. 98%

b. 88%

c. 78%

3. -------------------- itself is a common building material.

a. Limestone

b. Hydroxide

c. washing powder

4.The chemical formula of calcium carbonate is --------------.

a. CaCO₃

b. CCO₃

c. CaCO₂

5. ------of the steel inside the concrete can be a serious problem, weakening a structure.

 

a. Corrosion

b. Acid

c. Base

6. Concrete is the most widely used building material in the --------------.

 

a. world

b. Hydroxide

c. washing powder 

7. ----------------------- is made by mixing cement, sand and small stones.

a. Concrete

b. Hydroxide

c. washing powder 

8. -------------------- is one of the materials that we use to make glass.

 

a. Limestone

b. Hydroxide

c. washing powder

9. The first glass object has been dated at about -------------------- BC.

     a. 4500

b. 5500

c. 6500

10. -------------------- is a strange material.

a. Glass

b. Hydroxide

c. washing powder

11.The ---------------------- used glass containers around 3000 BC.

a. Egyptians

b. American

c. Sudanese

12.Some people call ---------------------- the 4th state of matter.

a. glass

b. hydroxide

c. washing powder