1. State the differences between acids and bases?

Acids 

• Acids are sour to taste.
• Acid turns blue litmus to red.
• Acid is a  substance which contains hydrogen ion(H+).
  

Bases

• Bases are bitter to taste.
• Base turns red litmus to blue.
• Bases are substances which contain hydroxyl ion (OH-).

2. Ammonia is found in many household products, such as window cleaners, It turns red litmus blue. What is its nature?

   Ammonia is  basic in  nature.

3. Name the source from which litmus solution is obtained. What is the use of this solution?

Litmus is extracted from lichens . It is most commonly used as an indicator to determine the chemical nature of substance.It has a mauve (purple) colour in distilled water. When added to an acidic solution, it turns red and when added to a basic solution, it turns blue. It is available in the form of a solution, or in the form of strips of paper, known as litmus paper. Generally, it is available as red and blue litmus paper. To test a substance for an Acid or a base or a neutral, litmus test is performed in which the Acid turns blue litmus red, Bases turn red litmus blue and has no effect on neutral substance.

4.Is the distilled water acidic/basic/neutral? How would you verify it?.

     The Distilled water is neutral. First, it is neither sour (Acidic) nor bitter (Basic), secondly to very its chemical nature, we can perform litmus test. It neither turns blue litmus red nor red litmus blue hence we can say, distilled water is neutral substance

5. Describe the process of neutralization with the help of an example?

     Neutralisation is a process in which an acid solution when mixed with base solution, react with each other to produce a salt and water along with generation of heat. Salt so produced, may be acidic, basic or neutral in nature.In this process the acidic nature of the acid and the basic nature of the base are destroyed. For Example : In the following reaction Hydrochloric acid (HCl) when added to Sodium hydroxide (NaOH) will produce Sodium chloride (NaCl) along with Water (H2O) and heat.

6. Dorji has a few bottles of soft drink in his restaurant. But unfortunately, these are not labelled. He has to serve the drinks on the demand of customers. One customer wants acidic drink, another wants basic and third one wants neutral drink. How will Dorji decide which drink is to be served to whom?

     Dorji can decide with the help of a litmus paper.

•  The drink which would turn a red litmus blue would be basic.
• If the drink turn a blue litmus to red, would be acidic.
• The drink which would not affect both red and blue litmus would be neutral.

7. Explain why: a. An antacid tablet is taken when you suffer from acidity  b. Calamine solution is applied on the skin when an ant bites    c. Factory waste is neutralized before disposing it into the water bodies?

• To get relief in digestion, we take an antacid such as milk of magnesia. It neutralizes the effect of excessive acid.
• Ant injects the acidic liquid into the skin on biting which cause inflammation to the skin. The effect of the sting can be neutralized by rubbing calamine solution which contains zinc carbonate, a weak base and causes no harm to the skin.
• The wastes of factories contain acids. If acids are disposed off water in the body, the acids will harm the organisms. So factory wastes are neutralized by adding basic substances.

8. Three liquids are given to you. One is hydrochloric acid, another is sodium hydroxide and third is a sugar solution. How will you identify them? You have only turmeric as indicator?

    Turmeric which is yellow in colur, when exposed to neutral (Sugar Solution) or acidic substances (Hydrochloric Acid) it will retain its yellow colouration. However, if turmeric is exposed to more alkaline substances (sodium hydroxide ) it becomes a dark pink/red. So first we detect sodium hydroxide -a basic substance by a colour change from yellow to dark or red. Then will test for an acid or neutral substance with indication of no coulr change. Now out of these two, we will mix one with already tested solution for basic substance -sodium hydroxide with dark or red colur, if on mixing the colour reverses back to yellow, the liquid is an acid and the remaining third liquid is neutral.

9. Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.

It can be identified on the basis of the following observations: Bases change the colour of litmus paper to blue. As the colour of blue litmus paper is not affected, the solution must be neutral.

10. Prepare red cabbage juice by boiling a piece of red cabbage in water. Use it is an indicator and test the acidic and basic solutions with it. Present your observations in the form of a table.We prepare the indicator by the boiling of red cabbage piece. Now we observe its effect on following substances?

Sl. No.     Substance     Colour on using Indicator     Nature of the Substance

1.       Lemon Juice        Pink                                  Acidic
2.      Orange Juice        Pink                                  Acidic
3.       Baking Soda       Green                                Base
4.       Curd                    Pink                                 Acidic
5.       Lime Water         Green                                Base

11. Bring a soil sample of your area. Find out if it is acidic, basic or neutral. Discuss it with farmers if they treat the soil in any manner?

     Take samples of soil from a field of your area. Mix the soil with water in a beaker. Stir well the mixture. Filter the mixture and take the filtrate in another beaker. Test it with litmus paper. If it converts blue litmus into red then it is acidic in nature. If it converts red litmus into blue then it is basic. If there is no effect on litmus paper then it is neutral. This is the best way to test the nature of the soil by the farmers.

12. Visit a doctor. Find out the medicines, he prescribes to treat acidity. Ask him how acidity can be prevented?

     We see that doctors prescribe some medicines to treat acidity. These medicines are basic in nature and called antacids. These medicines neutrilize the acidic effect of acids.

13. What are called indicators? Classify them and give one example of each?

The substances which are used to test whether a substance is acidic or basic are called indicators. There are two types of indicators (i) Natural indicators (ii) Man-made indicators. Natural indicators:- Litmus paper or solution. Man made indicators;- Phenolphthalein.

14. What is litmus? How is it prepared?

The most commonly used natural indicator is litmus. It is extracted from lichens. It has a purple colour in distilled water. It is available in the form of a solution or in the form of strips of paper. It is available as red and blue litmus paper.

15. Take tap water, vinegar and washing soda solution. Put a drop of these solutions on the red and blue litmus paper and write their observation in a tabular form?

Sl. No     Test Solution     Effect on red litmus paper     Effect on blue litmus paper     Inference

1.      Tap water                  No change                                 No change              Neutral
2.      Vinegar                      No change                                 Turns red                 Acidic
3.      Washing soda             Turns blue                                  No change              Basic

 16. How can you prepare turmeric paper?

     Take some turmeric powder and mix it in some water to make a paste. Deposit it on a blotting paper or filter paper and dry it. Cut thin strips of the yellow paper obtained. These thin strips are turmeric paper.

17. How can you prepare greeting card?

     You can prepare greeting card by using turmeric paste. To prepare a card for your friends, apply  turmeric paste on a sheet of plane white paper and dry it. Draw a beautiful flower with soap solution with the help of a cotton bud. You will get a beautiful greeting card.

18. What is acid rain?

     The rain containing excess of acid is called an acid rain. The  rain becomes acidic because carbon dioxide, sulphur dioxide and nitrogen dioxide which are released into air as pollutants, these are dissolved in rain drops to form acids. Acids rain can cause damage to buildings, historical monuments, plants and animals.

19. What do you mean by indigestion?

     Our stomach contains hydrochloric acid. It helps us to digest food. But too much of acid in the stomach causes indigestion. Sometimes indigestion is painful. To relieve indigestion we take an antacid such as milk of magnesia.

20. What is ant bite? What is its effect?

     The sting of an ant contains formic acid. When an ant bites, it injects the acidic liquid into the skin. It causes irritation and burning effect on skin. To relieve sting skin should be rubbed by moist baking soda or calamine which are basic in nature

21. What do you mean by soil treatment?

   When a farmer uses excessive chemical fertilizers in the soil then it becomes acidic. Plants do not grow well when the soil is either too acidic or too basic. When soil is too acidic, it is treated with base. If the soil is basic, some organic matter is added to it. Organic matter releases acids which neutralizes the basic nature of the soil. Soil treatment is used to make toxic soil for the use of agriculture. If soil contains any chemicals or wastes like oil, alkali or some other non-degradable material, we can degrade those toxic material by using microbes.