Samacheer Kalvi Class 8 Science Unit 11 Air Solutions
Welcome to NCTB Solutions. Here with this post we are going to help 8th class students by providing Solutions for Samacheer Kalvi Class 8 Science Unit 11 Air. Here students can easily find all the solved solution for Air Exercise questions. Also here our Expert Science Teacher’s solved all the questions with easily understandable language with proper guidance so that all the students can understand easily. Here on this post students will get Unit 11 Air exercise solutions. Here all the solutions are based on Tamil Nadu State Board latest syllabus.
Unit 11 Air Exercise Questions Solutions :
(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 :
Correct Option → (d)
The correct statement is – oxygen supports burning.
(2) Aerated water contains
(a) Air
(b) Oxygen
(c) Carbon dioxide
(d) Nitrogen
Answer :
Correct Option → (c)
Aerated water contains Carbon dioxide.
(3) Solvay process is a method to manufacture
(a) Lime water
(b) Aerated water
(c) Distilled water
(d) Sodium carbonate
Answer :
Correct Option → (d)
Solvay process is a method to manufacture 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 :
Correct Option → (a)
Carbon dioxide with water changes blue litmus to red.
(5) Which of the following is known as azote
(a) Oxygen
(b) Nitrogen
(c) Sulpher
(d) Carbon dioxide
Answer :
Correct Option → (b)
Nitrogen is known as azote.
(II) Fill in the blanks
(1) __ is called as 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 hydrated form of oxides is called __.
Answer :
(1) → Oxygen
(2) → Slightly lighter
(3) → Nitrogen
(4) → Refrigerant
(5) → Rusting
(IV) Answer briefly
(1) Mention the physical properties of oxygen.
Answer :
Physical properties of oxygen –
(a) Oxygen is a clourless , odourless and tasteless gas.
(b) It is a poor conductor of heat and electricity
(c) Oxygen dissolves readily in cold water.
(d) It is denser than air.
(e) It support combustion.
(2) List out the uses of nitrogen.
Answer :
The uses of nitrogen are as following :-
(a) Liquid nitrogen is used as a refrigerant.
(b) It is used as a substitute for compressed air in tyres.
(c) It is used as a fertilizer.
(d) Many explosives such as TNT, nitroglycerin and gun powder contain nitrogen.
(e) It is also used for preservation of foods, manufacturing of stainless steel, reducing fire hazard us and as a part of the gas in incandescent light bulbs.
(3) 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 → nitrogen compound.
For example : 3H2 + N2 → 2NH3
(4) What is global warming?
Answer :
The gases like carbon dioxide and methane mix in the atmosphere trap heat energy inside the atmosphere leads to increasing in temperature is known as Global warming.
(5) What is dry ice? What are its uses?
Answer :
When carbon dioxide is cooled it solidifies and this solid carbon dioxide is called dry ice. It is used as a coolant.
(V) Answer in detail
(1) What happens when carbon dioxide is passed through lime water? Write the equation for this reaction.
Answer :
When excess amount of carbon dioxide is passed through lime water, it first turns milky and the milkyness disappears due to the formation of soluble calcium hydrogen carbonate.
Equation : CO2 + Ca(OH)2 → Ca(HCO3)2
When limited amount of CO2 is passed through lime water it turns milkydue to the formation of insoluble calcium carbonate.
Equation : Ca(OH)2 + CO2 → CaCO3 + H2O
(2) Name the compounds produced when the following substances burn in oxygen.
(a) Carbon
(b) Sulphur
(c) Phosphorous
(d) Magnesium
(e) Iron
(f) Sodium
Answer :
| (Substances Burn) | (Compounds Produced) |
| (a) Carbon | Carbon dioxide (CO2) |
| (b) Sulfur | Sulfur dioxide (SO2) |
| (c) Phosphours | Phosphorus pentoxide (P4O10) |
| (d) Magnesium | Magnesium oxide ( MgO) |
| (e) Iron | Iron oxide (Fe2O3) |
| (f) Sodium | Sodium monoxide (Na2O) |
(3) How does carbon dioxide react with the following?
(a) Potassium
(b) Lime water
(c) Sodium hydroxide
Answer :
(a) Potassium : When potassium reacts with carbon dioxide forms potassium carbonate
2KOH + CO2 → K2CO3 + H2O
(b) Lime water : When carbon dioxide reacts with lime water it given calcium carbonate .
Ca(OH)2 + CO2 → CaCO3 + H2O
(c) Sodium hydroxide : When carbon dioxide is react with sodium hydroxide then it is a neutralization reaction between acid and base and product is formed is bicarbonate / salt and water.
NaOH + CO2 → NaHCO3+ H2O
(4) What are the effects of acid rain? How can we prevent them?
Answer :
The rain has pH less than 5.6 is known as acid rain.
- Effects of acid rain :
(a) It irritates eyes and skin of human beings.
(b) It inhibits germination and growth of seedlings.
(c) It changes the fertility of the soil, destroys plants and aquatic life.
(d) It causes corrosion of many buildings, bridges etc.
- Preventing measures for acid rain :
(a) Minimizing the usages of fossil fuel such as petrol, disel etc.
(b) Using CNG.
(c) Using non-conventional sources of energy.
(d) Proper disposal of the industrial wastes.
(VI) Higher Order Thinking Questions
(2) It is said that sleeping beneath the tree during night is not good for health. What is the reason?
Answer :
Sleeping beneath the tree during night is not good for health because at the night time trees released carbon dioxide gas which is harmful for us therefore it is not good for our health.
(3) Why does the fish die when it is taken out of water?
Answer :
Fish is die when we take it is from water because respiration process of fishers is done with the help of gills inside the water fist do not respire in atmospheric oxygen therefore when we taken fish out from water fish they cannot respire or live they die.
(4) How do astronauts breathe when they go beyond earth’s atmosphere?
Answer :
Astronauts carries oxygen cylinder for breathing when they go beyond earth’s atmosphere.
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