1. Chemistry Project~ By 3B TSUI MAN HUNG (29) WONG CHI WO (32)

2. Content P.2 Composition of sea water P.1 Profile of our work P.3-7 Details about sodium chloride P.8-9 Electrolysis of sea water P.10 Uses of products P.11 Conclusion

3. For our project, first of all we will talk about the composition of sea water.Then we will detach to two parts: In the first part is going to tell you some details about the main salt of sea water~sodium chloride. After that, we will also tell you about the electrolysis of sea water and uses of products. We hope you may enjoy it! Profile of our work

4. Composition of sea water Sea water is made up by water and salts, so it is very salty, and it contains many types of salts. Sea water is a solution, there is 35g of dissolved substances in 1000g of sea water.The main one is common salt (sodium chloride), which are used in kitchens. Salt composition of sea water

5. Sodium chloride (common salt) In last page, we can see that there are 68% of sodium chloride in sea water. We can take some pure sodium chloride by filtration or crystallization. Pure sodium chloride consists of sodium ions and chloride ions. But how can we test about them? Please go on to see the following pages.

6. How can we take the pure sodium chloride? Ⅰ. Filtration 1.Pour sea water onto the folded filter paper in a filter funnel 2.Use a glass rod to help the flow. The filter paper acts as a sieve 3.The liquid will pass though the filter paper. The solid are retained on the filter paper as residue. It includes sodium chloride inside.

7. Ⅱ. Crystallization How can we take the pure sodium chloride? (2) Sea water is allowed to evaporate at room temperature. The solution becomes more concentrated. Lastly the solution becomes saturated. And the evaporation of the solution will cause pure sodium chloride crystals to separate out. If the evaporation continues, the solid crystals will grow in size slowly.

8. Ions of pure sodium chloride consisted Ⅰ. Sodium ions (test for sodium ions) 1.Dip the platinum wire into a crushed or solution of salt to test 2.Heat strongly in a non- luminous flame 3.Then, we can see that there is given out a golden yellow flame So we can know that pure sodium chloride is included sodium ions inside.

9. Ⅱ. Chloride ions (test for chloride ions) Ions of pure sodium chloride consisted (2) 1.Add silver nitrate solutions to sea water 2.Followed excess dilute nitric acid 3.Appearance of a white precipitate indicates the presence of chloride ions So we can also know that, pure sodium chloride is included chloride ions inside.

10. Electrolysis of sea water After seeing the details about sodium chloride, we will change our focus on electrolysis of sea water. Sea water is an essential source of common salt (sodium chloride) which has many uses, such as using common salt to preserve fish. But we can get much more useful products by the electrolysis of sea water. Using common salt to preserve fish

11. Electrolysis means “decomposition by electricity”. It’s usually carried out by passing a direct electric current through an aqueous salt solution. When sea water is electrolyzed, the products are hydrogen, chlorine and sodium hydroxide. There is a concentrated solution of sodium called brine, which is used instead of sea water. Their main products are the same. Let’s see the uses of products in next page. Electrolysis of sea water (2)

12. Uses of products The uses of products (rocket fuel, soap, bleach, etc) are very useful for our life!

13. Conclusion We think that sea water (or oceans) is very important for our life. First, it acts the habitats of benthos. And we can take pure water by some methods, let us have water to use. Also, the sea water after electrolyzed, can help for our life a lot. It produces three kinds of products (gas/liquid), they help to fabricate some commodities, or treatment of water. It may also help for the development of industries, like food industry. So that, it is unimaginable that there are no any oceans or sea water in the world, it will let us very uncomfortable. But it may be there will be exhausted in the future. Therefore we should protect the ocean, don’t let them polluted.