Transcript 12. Building Materials and Rocks

1 of 36
© Boardworks Ltd 2006
2 of 36
© Boardworks Ltd 2006
What materials are used in buildings?
How are materials from the Earth used in construction?
3 of 36
© Boardworks Ltd 2006
Where do building materials come from?
Buildings are constructed
using materials from the Earth.
Some ‘cut rocks’, including
granite, marble and limestone,
make excellent building
materials.
Changing or combining rocks
from the Earth provides other
useful materials:
 glass is made from sand and limestone
 bricks are made from clay
 cement is made from limestone or clay.
4 of 36
© Boardworks Ltd 2006
How are rocks formed in nature?
The hardness and uses of a rock depend on how it is formed.
 Sedimentary rocks are made from
deposited sediments. They are relatively
soft and easy to shape. Limestone and
clay are sedimentary rocks.
 Metamorphic rocks are rocks changed
by heat or pressure. Marble is a
metamorphic rock that started as
limestone. It is harder than limestone.
 Igneous rocks are formed from cooled
magma from the inside of the Earth.
These rocks are very hard and difficult to
shape. Granite is a type of igneous rock.
5 of 36
© Boardworks Ltd 2006
Classifying rocks
6 of 36
© Boardworks Ltd 2006
What is cement?
Cement is used as a binder in concrete and mortar.
It is made by heating limestone or clay
and adding gypsum (a compound from
limestone). This mixture is then ground
into a powder.
After the powder is mixed with water,
it will harden to form a strong glue.
Mortar is made from cement, water
and sand. It is used in bricklaying and
stonework.
An even layer of mortar is spread
between the bricks or stones to hold
them firmly together.
7 of 36
© Boardworks Ltd 2006
How is concrete made?
Concrete is harder than mortar. It is sometimes described
as an artificial rock.
Concrete is made from sand,
cement and water but it is
harder than mortar because
it also contains gravel.
It is used for the foundations
of buildings and for large
structures, such as car parks.
What is the word equation for making concrete?
cement
8 of 36
+ sand +
gravel
+ water
 concrete
© Boardworks Ltd 2006
What is reinforced concrete?
Although concrete is a very hard material, it is not very
flexible. This means that when it is stretched it can break.
Concrete has a low resistance to tension forces.
Steel rods are used to increase the
strength and flexibility of concrete.
This is called reinforced concrete.
This material can support 300 to
500 times the combined mass of
steel and concrete it is made from.
Reinforced concrete has many
uses, including lamp-posts,
railways and as a structural
material to support buildings.
9 of 36
© Boardworks Ltd 2006
Building materials
10 of 36
© Boardworks Ltd 2006
11 of 36
© Boardworks Ltd 2006
What is limestone?
Limestone is an attractive pale yellow or grey stone.
Blocks of cut limestone are
used as a material for buildings
and statues.
Limestone is used during the
production of other building
materials including:
 cement
 mortar
 glass
 concrete
It is also used to extract impurities from iron in a blast
furnace, which produces a useable metal from iron ore.
12 of 36
© Boardworks Ltd 2006
How is limestone formed?
Limestone is a sedimentary rock. It is made over millions of
years by the compression of shells and skeletons.
It is quarried from the Earth for
use as a building material.
There are different types of
limestone, all containing a high
percentage of calcium
carbonate (CaCO3).
Limestone can become eroded
by rainwater.
Marble, a metamorphic rock formed from limestone,
also contains calcium carbonate. It is more expensive
than limestone but erodes more slowly.
13 of 36
© Boardworks Ltd 2006
Formation of limestone
14 of 36
© Boardworks Ltd 2006
What is thermal decomposition?
Limestone is a valuable material because it can be used as
the starting point for many other materials.
When limestone is heated strongly, a
chemical reaction takes place. Calcium
carbonate breaks down and forms calcium
oxide and carbon dioxide. This type of
reaction is called thermal decomposition.
A lime kiln is often used for this reaction.
The limestone is heated to 900 °C. This
method has been used for centuries.
What is the word equation for this reaction?
calcium
carbonate
15 of 36

calcium
oxide
+
carbon
dioxide
© Boardworks Ltd 2006
What about other metal carbonates?
Other metal carbonates can decompose in a similar way to
calcium carbonate, when they are heated.
For example, when magnesium carbonate is heated it
breaks down to form magnesium oxide and carbon dioxide.
magnesium
magnesium
carbonate 
oxide
+
carbon
dioxide
The general equation for the thermal decomposition of a
metal carbonate is:
metal
carbonate

metal
oxide
+
carbon
dioxide
What products are formed when copper carbonate
decomposes on heating?
16 of 36
© Boardworks Ltd 2006
Is this a balanced reaction?
During a chemical reaction, atoms are not created or
destroyed. This means that the numbers of atoms on both
sides of a balanced symbol equation are always the same.
calcium
carbonate
CaCO3

calcium
oxide
+
carbon
dioxide

CaO
+
CO2
element number of atoms
before reaction
17 of 36
number of atoms
after reaction
calcium
1
1
carbon
1
1
oxygen
3
1+2 = 3
© Boardworks Ltd 2006
Thermal decomposition
18 of 36
© Boardworks Ltd 2006
How is slaked lime made?
Calcium oxide, a product of the thermal
decomposition of limestone, is also
called quicklime.
Quicklime is used as an industrial drying
agent and to make slaked lime.
Uses of slaked lime include glass manufacture
and neutralization of the effects of acid rain.
Slaked lime is made by adding water to quicklime.
The chemical name for slaked lime is calcium hydroxide.
What is the word equation for this reaction?
calcium
oxide
19 of 36
+
water

calcium
hydroxide
© Boardworks Ltd 2006
Why does carbon dioxide turn limewater cloudy?
Fully dissolving calcium hydroxide in water forms limewater.
Limewater is used to test for carbon dioxide.
When carbon dioxide gas is bubbled through
limewater, the limewater becomes cloudy.
The carbon dioxide reacts with calcium hydroxide
to form calcium carbonate and water.
The solid calcium carbonate is held in suspension,
which gives the limewater a cloudy appearance.
What is the word equation for this reaction?
calcium
hydroxide (aq)
20 of 36
+
calcium
carbon
dioxide  carbonate
+
water
© Boardworks Ltd 2006
Summary of uses of limestone products
The products of limestone have many uses.
Quicklime, calcium oxide, is used in making
steel and as an industrial drying agent. It can
be mixed with water to form slaked lime.
Slaked lime, calcium hydroxide, is used to
make the building materials mortar and glass.
Slaked lime is alkaline. It can be sprayed on
agricultural fields to reduce soil acidity and
on lakes to neutralize the effects of acid rain.
Limewater is made by fully dissolving slaked
lime in water. It is often used to test for carbon
dioxide. This is because limewater turns cloudy
in the presence of carbon dioxide.
21 of 36
© Boardworks Ltd 2006
Summary of limestone chemistry
Limestone and its products can be involved in various useful
chemical reactions:
 thermal decomposition of limestone
calcium
carbonate

calcium
oxide
+
carbon
dioxide
 production of slaked lime
calcium
oxide
+
water

calcium
hydroxide
 using limewater to test for carbon dioxide.
calcium
hydroxide (aq)
22 of 36
+
calcium
carbon
dioxide  carbonate
+
water
© Boardworks Ltd 2006
How does quarrying affect the environment?
Limestone is an essential
building material. Millions of
kilograms of limestone are
extracted every year for use in
construction and industry.
However, quarrying limestone
can cause environmental
damage.
 Limestone is often found in areas of outstanding natural
beauty. Quarrying can leave scars on the landscape.
 Explosives used in quarrying produce noise and dust.
 Air and noise pollution is caused by lorries transporting
limestone from the quarry.
23 of 36
© Boardworks Ltd 2006
Impacts of limestone quarrying
24 of 36
© Boardworks Ltd 2006
Quarrying limestone
25 of 36
© Boardworks Ltd 2006
26 of 36
© Boardworks Ltd 2006
How is salt produced?
Seawater and rock salt can be used to make table salt.
The scientific name for table salt is sodium chloride.
It has the formula NaCl.
Salt is found dissolved in
seawater. When the water
evaporates it leaves
deposits of salt.
Ancient oceans have
deposited salt in salt beds
or underground rocks.
These can be mined and
processed.
27 of 36
© Boardworks Ltd 2006
What is salt used for?
Sodium chloride is a useful compound.
In winter, rock salt can be used
on roads to melt ice. This is
because salt lowers the melting
point of ice. The salt does not
need to be pure for this use.
Salt is used to flavour food. It can also be
used to preserve food. White table salt is
processed to remove impurities.
Chemicals produced from the electrolysis
of salt and brine (salt dissolved in water)
are also very valuable.
28 of 36
© Boardworks Ltd 2006
Electrolysis of salt water solution
29 of 36
© Boardworks Ltd 2006
Using products from salt
30 of 36
© Boardworks Ltd 2006
Using salt
31 of 36
© Boardworks Ltd 2006
32 of 36
© Boardworks Ltd 2006
Glossary (1/2)
 brine – Sodium chloride (table salt) dissolved in water.
 cement – A product of limestone. It is used as a binder in







mortar and concrete.
concrete – A mixture of cement, sand, gravel and water.
It is used in construction.
electrolysis – The use of electricity to split a compound.
granite – A type of igneous rock that is harder than
limestone and marble.
igneous – A rock formed from cooled magna.
limestone – A type of sedimentary rock containing
calcium carbonate.
limewater – A limestone product made by fully dissolving
quicklime in water. It is used to test for carbon dioxide.
marble – A type of metamorphic rock that is harder than
limestone but softer than granite.
33 of 36
© Boardworks Ltd 2006
Glossary (2/2)
 metamorphic – A rock changed by pressure and heat.
 mortar – A mixture of cement, sand and water. It is used in






bricklaying and stonework.
quicklime – A product of the thermal decomposition of
limestone. Also called calcium oxide.
reinforced concrete – A type of concrete containing
steel rods for extra strength.
sedimentary – A rock formed by the deposition of
sediments.
slaked lime – A limestone product made by adding water
to quicklime. Also called calcium hydroxide.
sodium chloride – The scientific name for table salt.
thermal decomposition – The breakdown of a
compound into simpler substances by heating.
34 of 36
© Boardworks Ltd 2006
Anagrams
35 of 36
© Boardworks Ltd 2006
Multiple-choice quiz
36 of 36
© Boardworks Ltd 2006