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The importance of water

Module by: Siyavula Uploaders. E-mail the author

NATURAL SCIIENCES

Grade 5

PLANET EARTH AND THE UNIVERSE

Module 24

THE IMPORTANCE OF WATER

activity:

TO BE ABLE TO EXPLAIN WHY WATER IS IMPORTANT FOR LIFE ON EARTH, HOW THE PLANET MAINTAINS ITS WATER BALANCE AND WHY SENSIBLE WATER CONSUMPTION IS IMPORTANT

[LO 2.1; LO 3.2]

The importance of water

Without water, life is impossible. Let us examine a few examples that illustrate the importance of water for plants and animals:

  • Water makes up about 80% of the body of a land plant, and about 60% of the body of a human. It is this water in the bodies of animals and plants that prevents the temperature of the plant or animal from rising too high when it is hot outside, or from falling too low when it is cold.
  • Water evaporation helps plants and animals to cool down their bodies (in the form of perspiration in animals and, in the case of plants, in the form of moisture that is exuded from mainly the leaves).
  • The process of exchanging gases when breathing takes place is only possible if the surface is moist.
  • Blood flows only because it consists mainly of water.
  • The process of conveying nutrients within a plant would not be possible without water.
  • Food digestion is only possible if there is sufficient water.
  • Many plants and animals live in water.
  • Various animals that live on land can only procreate if there is sufficient water, e.g. the frog.

Earth’s water supply

The earth’s water supply is never replenished from space, as is the case with solar energy, which we get from the sun.

However, nature has developed mechanisms to maintain the earth’s water supply. In this way, for example, water in nature is used over and over and we speak of water cycles.

Unfortunately, humans are inclined to disturb these water cycles with their activities. Examples of this are the way in which huge industries use water, the destruction of indigenous vegetation, pollution and water wastage.

See whether you are able to mention ten examples of water wastage, water pollution or indiscriminate use of water.

THE WATER CYCLE

The largest part of planet Earth is covered by water (70%). That is why Earth looks blue on photos that are taken from satellites.

Besides this visible surface water there is also a great deal of subterranean water.

The water is distributed by means of subterranean canals (underground watercourses) and rivers on the earth’s surface.

As a result of the warming effect of the sun, this water is not icy cold everywhere.

The warming effect causes a huge amount of water to rise into the air every day as it evaporates from dams, rivers, lakes and oceans.

As the vapour rises, it cools down and condenses to form droplets of water. This is how clouds are formed.

When conditions are favourable, the water in the clouds falls to earth again in the form of rain. This process repeats itself continuously and we refer to it as the water cycle.

Figure 1
Figure 1 (graphics1.png)

1. Describe the water cycle in your own words.

2. What would happen to the water cycle if the heat of the sun were to decrease or if the sun were to stop shining altogether?

3. Explain how rain is formed.

4. Name and explain four ways in which humans disturb the water cycle.

Assessment

LEARNING OUTCOME 2: CONSTRUCTION OF SCIENTIFIC KNOWLEDGELearners know, interpret and apply scientific, technological and environmental knowledge.

We know this when the learner:

2.1 recalls significant information;

2.2 categorises information

LEARNING OUTCOME 3: Science, SOCIETY and the environmentLearners are able to show understanding of the underlying connections of technology, the community and the environment.

ASSESSMENT STANDARDS

We know this when the learner:

3.1 understands science and technology in the context of history and indigenous knowledge:

3.1.1 describes traditional shelters and connects some features of such shelters with modern dwellings.

Memorandum

A few examples (there are many: give the learners the opportunity to talk to people at home and to find examples: it creates a consciousness in the community of this problem):

Waste/indiscriminate use

  • Pipes and taps that leak
  • Taps that are not closed properly
  • Trees are planted in areas that have ample water (especially plantations)
  • Alien plants are allowed to intrude and encroach on indigenous ones
  • No dams are being built

Pollution

  • Insufficient sanitation
  • Rubble
  • Industrial waste
  • Alien plants are allowed to grow in water (drive indigenous plants out, upset the balance, plants and animals die, sediment and decomposition removes oxygen from the water)
  • Vehicle exhaust fumes contribute to the occurrence of acid rain

Water cycle

  • Description must contain the following: evaporation, cloud formation, types of precipitation, e.g. rain, underground water, rivers, dams, lakes and oceans
  • Evaporation would stop and the water would just stay where it is
  • Evaporation, cooling, condensation, and cloud formation

4. Destruction of indigenous vegetation

Large-scale overgrazing (desert forming)

Indiscriminate change of the natural flow of water

Destruction of the ozone layer, pollution: global warming, warming of the oceans, rainfall patterns disturbed

Indiscriminate establishing of plantations (in areas with plentiful water)

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