Samacheer Kalvi 8th Science Unit 11 Book Back Answers:

Samacheer Kalvi 8th Standard New Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 8 New Syllabus 2021 to 2022 Book Back Question & Answer available for both English and Tamil Mediums. Class 8th Science Book Unit 11 – Air Answers/Solutions are provided on this page. 8th Std Science Book consists of 23 units, All Science Book Back One, and Two Mark Solutions are given below.

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Samacheer Kalvi 8th Science Book Back Solutions PDF:

8th Science Subject 1 Mark and 2 Mark Solutions PDF available below. Click the Download option to download the book back 1 Mark & 2 Mark questions and answers. Take the printout and use it for exam purposes. Samacheer Kalvi 8th Science Unit 11 Answers are given below.

Science Book Back Answers

Unit 11 – Air

I. Choose the best answer

1. Which of the following is true about oxygen?
(a) Completely burning gas
(b) Partially burning gas
(c) Doesn’t support burning
(d) Supports burning
Answer: (d) Supports burning

2. Aerated water contains –
(a) air
(b) oxygen
(c) carbon dioxide
(d) nitrogen
Answer: (c) carbon dioxide

3. Solvay process is a method to manufacture –
(a) lime water
(b) aerated water
(c) distilled water
(d) sodium carbonate
Answer: (d) sodium carbonate

4. Carbon dioxide with water changes –
(a) blue litmus to red
(b) red litmus to blue
(c) blue litmus to yellow
(d) doesn’t react with litmus
Answer: (a) blue litmus to red

5. Which of the following is known as azote?
(a) Oxygen
(b) Nitrogen
(c) Sulphur
(d) Carbon dioxide
Answer: (b) Nitrogen

II. Fill in the blanks:

1. ……………. is called a vital life.
2. Nitrogen is ……………. than air.
3. ……………. is used as a fertilizer.
4. Dry ice is used as a …………….
5. The process of conversion of iron into the hydrated form of oxides is called …………….

Answer:

1. Oxygen
2. lighter
3. Nitrogen
4. refrigerant
5. rusting

III. Match the following

Question 1.

1. Nitrogen – Respiration in living animals
2. Oxygen – Fertilizer
3. Carbon dioxide – Refrigerator
4. Dry ice – Fire extinguisher

Answer:

1. Nitrogen – Fertilizer
2. Oxygen – Respiration in living animals
3. Carbon dioxide – Fire extinguisher
4. Dry ice – Refrigerator

IV. Answer briefly

1. What are the sources of oxygen?
Answer:

1. Atmospheric air, water.
2. Plants and animals.
3. Minerals in the form of silicates, carbonates, and oxides.

 2. Mention the physical properties of oxygen.
Answer:
Physical properties of oxygen:

1. Oxygen is a colorless, odorless and tasteless gas.
2. It is a poor conductor of heat and electricity
3. Oxygen dissolves readily in cold water.
4. It is denser than air.
5. It can be made into liquid (liquefied) at high pressure and low temperature.
6. It supports combustion.

3. List out the uses of nitrogen.
Answer:
Uses of nitrogen:

1. Liquid nitrogen is used as a refrigerant.
2. It provides an inert atmosphere for conducting certain chemical reactions.
3. It is used to prepare ammonia (by Haber’s process) which is then converted into fertilizers and nitric acid.
4. It is used for inflating tyres of vehicles.

4. Write about the reaction of nitrogen with non metals.
Answer:
Nitrogen reacts with non-metals like hydrogen, oxygen etc., at high temperature to form their corresponding nitrogen compounds.
Non-metal + Nitrogen Δ→ Nitrogen compound
Example:

5. What is global warming?
Answer:
The increased green house effect is caused due to increase in the air pollutants and it results in the average increase of temperature of the atmosphere. This is called as Global warming.

6. What is dry ice? What are its uses?
Answer:

1. Solid carbon dioxide, called as dry ice is used as a refrigerant.
2. The gas is so cold that moisture in the air condenses on it, creating a dense fog which is used in stage shows and movie effects.

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