Chemistry

What is hard water? advantages and disadvantages of hard water.  Hard water Find it difficult to make a lather with soap. Bits of white scum will float around in the water when you use soap. However, it does have its advantages. Look at this table: Disadvantages of hard water Difficult to form lather with soap. Scum forms in a reaction which wastes soap. Scale (a hard crust) forms inside kettles. This wastes energy when you boil your kettle. Hot water pipes fur up' on the inside. The scale formed can even block up pipes completely.     Advantages of hard water Some people prefer the taste. Calcium in the water is good for children's teeth and bones. Helps to reduce heart illness. Some brewers like hard water for making beer A coating of scale (limescale) inside copper or lead pipes stops poisonous salts dissolving into our water.   Let's see if we can find out why some water is hard: Experiment 22.1 What causes hardness i...

Define Aeration Sedimentation Filtration  Chemical purification.     Drinking water Did you know that about two-thirds of the mass of your body is made up of water?   So it's not surprising that we should drink between 6 and 8 glasses of water everyday. You don't want to shrivel up like a dried prune. We are lucky that we have drinking water 'on tap. Many people around the world have to collect their own water, often from contaminated sources. We looked at the important job that chlorine does in making water safe to drink on page 55. Now we can follow the journey of water, from a reservoir to our taps at home. Let's look at the ways we treat water to make it safe to drink: Aeration The water is stirred up to let air (oxygen) mix with it. This can also be done by letting it fall down steps. This helps to remove iron(l|) ions in the water. They precipitate out as iron(III) hydroxide. If this happens in your water at home...

   Ocean                These salts have entered the oceans following their weathering from rocks on land. The dissolved salts are carried to the sea by rivers. why don't the proportions of salts build up over time? This is explained by chemical precipitation As new salts enter the sea, other salts are being deposited on the ocean floor as solids. Equilibrium has been reached. The oceans also contain dissolved gases. These come from volcanic activity on the sea bed and from the gases in the air. The oceans play an important part in the carbon cycle as reservoirs for carbon dioxide. The carbon dioxide can form hydrogen carbonates which are soluble in the sea water.     Assessment   1.    New salts enter the sea, other salts are being deposited         on the ------------------ floor as solids. A.   Car B.   ocean C. Mobile ...