Welcome to the detailed overview of the Chemistry course material focusing on the topic of Water. In this section, we will delve into various aspects related to water, including its composition, properties, uses, and treatment methods.

Water is an essential molecule for life on Earth, with a wide range of uses in various fields. It is composed of two hydrogen atoms bonded to one oxygen atom, forming a polar molecule with unique properties. One crucial aspect to understand is that water can dissolve a variety of substances due to its polarity, making it a universal solvent.

One of the key objectives of this course is to identify the effects of dissolved atmospheric gases in water. Water can dissolve gases such as oxygen, carbon dioxide, and nitrogen from the atmosphere. These dissolved gases play vital roles in biological processes, such as respiration and photosynthesis, highlighting the importance of understanding water as a solvent.

Furthermore, we will distinguish between the properties of hard and soft water. Hard water contains high levels of dissolved minerals, primarily calcium and magnesium ions, which can lead to issues such as scale buildup in pipes and appliances. On the other hand, soft water has lower mineral content and is preferred for tasks like laundry and bathing.

To address the challenges posed by hard water, it is crucial to identify the causes of hardness and explore methods for its removal. Techniques such as ion exchange, distillation, and reverse osmosis are commonly employed to soften hard water and improve its usability in various applications.

Another critical aspect we will cover is the treatment of water for town supply. Ensuring access to clean and safe drinking water involves processes like filtration, chlorination, and fluoridation to remove contaminants and microorganisms. Understanding these treatment methods is vital for maintaining public health and preventing waterborne diseases.

Lastly, we will explore phenomena related to water crystallization, efflorescence, deliquescence, and hygroscopy. These phenomena involve the absorption and release of water molecules by certain compounds, leading to distinct physical changes. By studying examples of substances exhibiting these properties, such as hydrated salts and desiccants, we can appreciate their practical applications in various industries.


  1. Determine The Causes Of Hardness
  2. Identify The Various Uses Of Water
  3. Distinguish Between These Phenomena
  4. Distinguish Between The Properties Of Hard And Soft Water
  5. Describe The Processes Involved In The Treatment Of Water For Town Supply
  6. Identify The Various Compounds That Exhibit These Phenomena
  7. Identify The Effects Of Dissolved Atmospheric Gases In Water
  8. Identify Methods Of Removal Of Hardness

Lesson Note

Composition of Water

Lesson Evaluation

Congratulations on completing the lesson on Water. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

  1. What is the main difference between hard water and soft water? A. Amount of minerals dissolved in water B. Presence of impurities in water C. Temperature at which water freezes D. pH level of the water Answer: A. Amount of minerals dissolved in water
  2. Which of the following is NOT a method of softening hard water? A. Distillation B. Ion exchange C. Filtration D. Boiling Answer: C. Filtration
  3. What is the purpose of adding chlorine during the treatment of water for town supply? A. To remove hardness B. To kill bacteria and viruses C. To improve taste D. To reduce pH level Answer: B. To kill bacteria and viruses
  4. Efflorescence is the loss of water of crystallization by a compound due to exposure to air. Which substance commonly exhibits efflorescence? A. Sodium chloride B. Magnesium sulfate C. Calcium carbonate D. Potassium permanganate Answer: A. Sodium chloride
  5. Which phenomenon involves the gradual uptake of water vapor from the air by a compound? A. Hygroscopy B. Deliquescence C. Efflorescence D. Condensation Answer: A. Hygroscopy

Recommended Books

Past Questions

Wondering what past questions for this topic looks like? Here are a number of questions about Water from previous years

Question 1 Report

(a)i. With the aid of an equation, explain briefly why aluminum metal is not affected by air.

(ii) In the extraction of aluminum from bauxite, state the:
- substance used for purifying the ore;
- composition of the mixture electrolyzed.

(b) ZnO is an amphoteric oxide. Write equations to illustrate this statement.

(c)i) List three uses of sodium trioxocarbonate(IV).

(ii) Explain briefly why a solution of trioxonitrate(V) acid turns yellowish on storage for some time.

(ii) Describe briefly how trioxonitrate(V) ions could be tested for in the laboratory.

(d) Write balanced chemical equations for the preparation of hydrogen chloride.

(i) using concentrated H\(_{2}\)SO\(_{4}\):

(ii) by direct combination of its constituent elements.

(iii) State one use of hydrogen chloride. 

Question 1 Report

Sulphur has an oxidation number of +4 in

Question 1 Report

Which of the following methods is commonly used to remove suspended impurities from water?

Practice a number of Water past questions