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8th Standard
TN 8th Tamil இயல் 3 - கல்வி கரையில - வினைமுற்று Important Questions And Answers Study Material - QB365 Set A
NEW8th Standard
TN 8th Tamil இயல் 2 - ஈடில்லா இயற்கை - மயங்கொலிகள் Important Questions And Answers Study Material - QB365 Set A
NEW8th Standard
TN 8th Tamil இயல் 2 - ஈடில்லா இயற்கை -பட்டமரம் Important Questions And Answers Study Material - QB365 Set A
NEW8th Standard
TN 8th Tamil இயல் 2 - ஈடில்லா இயற்கை - இயற்கையை போற்றுவோம் Important Questions And Answers Study Material - QB365 Set A
NEW8th Standard
TN 8th Tamil இயல் 1 - தமிழ் இன்பம் - ஆழிக்கு இணை Important Questions And Answers Study Material - QB365 Set A
NEW8th Standard
TN 8th Tamil இயல் 2-ஈடில்லா இயற்கை - திருக்குறள் Important Questions And Answers Study Material - QB365 Set A
Published on: 30/07/2019
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Download Tamil Nadu 8th Standard Science question papers, model tests, one-mark questions, important questions, and public exam papers in PDF format. Free study materials and answer keys for TN State Board students.
Questions + Answers key
Take MCQ Science Test1.
Rusting of iron is a _________ change.
physical
chemical
physical and chemical
neutral
2.
______ is responsible for Global warming.
Carbon di oxide
methane
chlorofluoro carbons
all the above
3.
In Haber’s process of producing ammonia ______ is used as a catalyst.
Nitrogen
hydrogen
iron
nickel
4.
Brine is a concentrated solution of ______.
Sodium sulphate
sodium chloride
calcium chloride
sodium bromide
5.
The burning of matchstick is an example for chemical reaction based on______
Contact in physical states
electricity
light
catalyst
6.
Burning of paper is a______ change.
Physical
chemical
physical & chemical
neutral
7.
The sides of the matchbox contains _________
8.
______ is the enzyme responsible for browning of vegetables, fruits.
9.
Electrolysis of Brine solution gives ______ gases.
10.
Iron objects undergo rusting when exposed to ______ and ______.
11.
Reactants → ______.
12.
Calcium oxide
13.
Tarnishing
14.
Catalysis
15.
Thermolysis
16.
Rusting
17.
What is rusting?
18.
Why photosynthesis is a chemical reaction?
19.
What is pollution?
20.
Define a chemical reaction.
21.
Explain any three conditions that is required for a chemical reaction to take place. Give example.
22.
Explain the three types of pollution.
23.
Do all the fruits and vegetables undergo browning? Explain.
24.
Explain the role of yeast in making cakes and buns in a bakery?
25.
Silver articles become black on exposure to atmospheric air
26.
In vanaspathi ghee (dalda) preparation finely divided platinum is used as a catalyst.
27.
Brine solution undergoes photolysis to give hydrogen and chlorine gas along with sodium hydroxide.
28.
Iron in water and air: Brown colour :: Iron in copper sulphate solution:_________
29.
Fertilizers: Land pollution :: Oil spillage: _________
1.
(b)
chemical
2.
(d)
all the above
3.
(c)
iron
4.
(b)
sodium chloride
5.
(a)
Contact in physical states
6.
(b)
chemical
7.
( )
Red phosphorous
8.
( )
Polyphenol oxidase or tyrosinase.
9.
( )
Chlorine and hydrogen
10.
( )
Water and oxygen
11.
( )
Products
12.
Decomposition
13.
Chemical reaction
14.
Haber's process
15.
Decomposition of limestone
16.
Iron
17.
Rusting is a chemical reaction in which iron objects form hydrated ferric oxide in the presence of oxygen and water.
18.
Photosynthesis is an irreversible change. In photosynthesis carbondioxide and water react in the presence of sunlight to produce a new substance called starch. Hence photosynthesis is a chemical reaction
19.
Any unwanted change in physical, chemical and biological properties of the environment is termed as pollution.
20.
i) A chemical change is a permanent, irreversible change and produces a new substance.
ii) chemical changes are otherwise called as chemical reactions.
21.
(i) Chemical reactions based on contact:
Certain chemical reactions take place only when the reactants are brought in contact with each other in their physical states.
Eg: When quicklime comes in contact with water, it forms slaked lime.
(ii) Chemical reactions based of solution of reactants:
When we mix two substances in solution form, the chemical reaction takes place to form new substances.
Eg: Barium chloride solution reacts with sulphuric acid solution to form barium sulphate as a white precipitate and hydrochloric acid.
(iii) Chemical reactions based on electricity:
Some chemical reactions proceed only by the passage of electricity. Such reactions are called electrochemical reaction or electrolysis.
Eg: When Brine is electrolysed it produces chlorine and hydrogen gases along with sodium hydroxide.
22.
| S.No | Type of pollution | Chemical substances responsible for the pollution | Effects |
|---|---|---|---|
| 1 | Air pollution | Carbon dioxide, Carbon monoxide, oxides of sulphur, oxides of nitrogen, Chlorofluorocarbons, methane etc. | Acid rain, Global warming, respiratory problems etc |
| 2 | Water pollution | Wastewater containing chemical substances (eg. dyeing industries), detergents, oil spillage etc. | Decrease in quality of water, skin diseases etc |
| 3 | Land pollution | Fertilizers like urea, various pesticides, herbicides etc | Spoilage of land, cancer, respiratory diseases etc. |
23.
No, all the fruits and vegetables do not undergo browning. The cells of certain fruits like apples contain an enzyme called tyrosinase when in contact with oxygen catalyses a biochemical reaction of plant's phenolic compounds to brown pigments. So, the fruits and vegetables which contain tyrosinase undergo browning.
24.
Yeast is a biocatalyst when yeast is added while making cakes
i) it triggers fermentation
ii) it releases carbondioxide which results in the expansion of dough.
iii) it is responsible for the soft porous texture of the cake
iv) It is the keyfactor behind the characteristic bakery flavour of a cake.
25.
True
26.
False. In vanaspathi ghee (dalda) preparation finely divided nickel is used as a catalyst.
27.
False. Brine solution undergoes electrolysis to give hydrogen and chlorine gas along with sodium hydroxide.
28.
Green colour
29.
Water pollution
8th Standard Syllabus & Materials
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TN 8th Tamil இயல் 3 - கல்வி கரையில - பாடறிந்து ஒழுகுதல் Important Questions And Answers Study Material - QB365 Set A
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Tamilnadu Stateboard 8th Standard Subjects
Tamilnadu Stateboard Standards
