1. Natural Sciences Grade 7
Term 2: Matter and Materials
Properties of materials
(PPT 2)

2. Topic 1 Properties of materials
Impact on the environment
Natural Sciences - Grade 7

3. Mining precious metals : Gold (1)
Mining process – sinking shafts deep into the ground and blasting the rock that contains gold ore.
Chemicals are used in the mines when the gold ore is processed in order to extract the gold.
Most chemicals harm the environment and it causes water pollution in the dams and rivers that are close by.
The rocks that are mined for the gold are dumped on mine dumps and the dust has a bad influence on the health of people.
Natural Sciences - Grade 7

4. Mining precious metals : Gold (2)
Plants hardly grow on these mine dumps, because the chemicals damage the soil.
Water mixes with the chemicals as it moves through the mining tunnels and sulphuric acid is formed.
It flows into rivers and streams and pollutes the groundwater when it is pumped from the boreholes.
Natural Sciences - Grade 7

5. Mining precious metals : Gold (3)
It is the responsibility of mining companies to rehabilitate the mining site after it had closed down.
Natural Sciences - Grade 7

6. Natural Sciences - Grade 7
Plastic (2.1)
Plastic bags:
are mostly made from polyethylene (petroleum
and natural gas).
are convenient, strong, lightweight, cheap and
useful.
have a very negative influence on the
environment.
Natural Sciences - Grade 7

7. Natural Sciences - Grade 7
Plastic (2.1)
Plastic bags:
litter is a very serious concern (blocks/clogs
drains that lead to flooding , blown into the seas /
rivers where the aquatic animals choke when
they eat it or they strangle / starve / suffocate
when the plastic entangles around their bodies.
Natural Sciences - Grade 7

8. Natural Sciences - Grade 7
Plastic (2.1)
Plastic bags:
between 500 billion and 1 trillion disposable bags are used annually around the world
pieces of plastic bags outnumber the mass of plankton in the sea water
Natural Sciences - Grade 7

9. Natural Sciences - Grade 7
Plastic (2.1)
Plastic bags:
it can cost cities and states millions of dollars / rands / etc. to clean up and properly dispose of plastic bags
some businesses offer a small discount for utilizing reusable bags, instead of plastic bags
laws that either ban plastic bags entirely or place a fee on them have been implemented in some
countries
The South African law to charge customers for plastic bags, came into effect in 2003.
Thicker reusable plastic bags replaced the thinner ones.
Natural Sciences - Grade 7

10. Natural Sciences - Grade 7
Plastic (2.2)
Plastic waste is dumped on landfill sites to decompose (it takes almost years to decompose, releasing substances into the soil that are poisonous for the microorganisms and plant life).
Most plastic is not biodegradable.
Plastic waste in landfills that are burned releases toxic chemicals and gases into the air.
8% of world oil production goes into plastic manufacturing
Every square km of the ocean has approximately pieces of plastic litter which kill more than 1 million marine life annually
Between Asia and the United States of America there is a place filled with plastic litter and it is called the Great Garbage Patch (it is twice the size of Hawaii) – pictures 2 & 3 (Great Pacific Garbage Patch - Ocean Pollution Awareness - (2:59)
Natural Sciences - Grade 7

11. Natural Sciences - Grade 7
Plastic (2.2)
Human beings must use less plastic, reuse plastic shopping bags, use fabric bags so that the environment can be protected.
Plastic objects are usually only used once/twice before it is thrown away.
Natural Sciences - Grade 7

12. Natural Sciences - Grade 7
Fuels (3)
Getting the fossil fuel sources of energy (oil, coal , natural gases) has an impact on the environment.
Cars and other forms of transport use diesel / petrol which is made from oil. The oil is between layers of rock, mostly in the sea bed.
From the oil rigs on the sea, a well is drilled into the rock and the oil is pumped up
to the ground and transported in big
oil tanker ships along pipelines.
Natural Sciences - Grade 7

13. Natural Sciences - Grade 7
Fuels (3)
Damaged oil tankers /pipelines cause oil spills that reach marine animals’ habitats and it causes the death of marine plants and animals.
The effects of oil spills on Earth
Airways and lungs of marine mammals are damaged by breathing in droplets of oil, oil fumes or gases
Congestion and stomach ulcers / bleeding
Natural Sciences - Grade 7

14. Natural Sciences - Grade 7
Fuels (3)
South Africa uses coal, which must be mined, as its main fuel to generate electricity.
Natural gas is used as a energy source for generating electricity, heating and cooking.
Fossil fuels release harmful gases (carbon monoxide and carbon dioxide) when they are burned and it contributes to air pollution.
Natural Sciences - Grade 7