Chemistry_Grade_10-12 (1).pdf

A write a balanced equation for the reaction that

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(a) Write a balanced equation for the reaction that takes place. (b) Does a precipitate form during the reaction? (c) Describe a test that could be used to test for the presence of barium sulphate in the products. 3. A test tube contains a clear, colourless salt solution. A few drops of silver nitrate solution are added to the solution and a pale yellow precipitate forms. Which one of the following salts was dissolved in the original solution? (a) NaI (b) KCl (c) K 2 CO 3 (d) Na 2 SO 4 (IEB Paper 2, 2005) 392
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CHAPTER 20. THE HYDROSPHERE - GRADE 10 20.9 20.9 Threats to the Hydrosphere It should be clear by now that the hydrosphere plays an extremely important role in the survival of life on Earth, and that the unique properties of water allow various important chemical processes to take place which would otherwise not be possible. Unfortunately for us however, there are a number of factors that threaten our hydrosphere, and most of these threats are because of human activities. We are going to focus on two of these issues: overuse and pollution and look at ways in which these problems can possibly be overcome. 1. Overuse of water We mentioned earlier that only a very small percentage of the hydrosphere’s water is available as freshwater. However, despite this, humans continue to use more and more water to the point where water consumption is fast approaching the amount of water that is available . The situation is a serious one, particularly in countries such as South Africa which are naturally dry, and where water resources are limited. It is estimated that between 2020 and 2040, water supplies in South Africa will no longer be able to meet the growing demand for water in this country. This is partly due to population growth, but also because of the increasing needs of industries as they expand and develop. For each of us, this should be a very scary thought. Try to imagine a day without water...difficult isn’t it? Water is so much a part of our lives, that we are hardly aware of the huge part that it plays in our daily lives. Activity :: Discussion : Creative water conservation As populations grow, so do the demands that are placed on dwindling water resources. While many people argue that building dams helps to solve this water- shortage problem, the reality is that dams are only a temporary solution, and that they often end up doing far more ecological damage than good. The only sustainable solution is to reduce the demand for water, so that water supplies are sufficient to meet this. The more important question then is how to do this. Discussion: Divide the class into groups, so that there are about five people in each. Each group is going to represent a different sector within society. Your teacher will tell you which sector you belong to from the following: Farming, industry, city management or civil society (i.e. you will represent the ordinary ’man on the street’). In your groups, discuss the following questions as they relate to the group of people you represent: (Remember to take notes during your discussions,
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