Samacheer Kalvi 9th Term III Science Book Back Question and Answers – Unit 4:

Samacheer Kalvi 9th Standard New Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 9 New Syllabus 2021 to 2022 Book Back Question & Answer solutions available for both English and Tamil Medium. Class 9 Science Book Term 3 Unit 4 – Planets in Orbit Answers/Solutions are provided on this page. 9th Std Science Book is of Term 1st, 2nd, 3rd, and consists of 9 Units in each Term. All 9 Units of Term 1st, 2nd, 3rd Science Book Back One, and Two Mark Solutions are given below.

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Samacheer Kalvi 9th Science Book Back Term 3 Unit 4 Solutions Guide PDF:

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Term – 3

Unit – 4 Planets in Orbit

I. Choose the correct answer:

1. A phenomenon in which an element exists in different modification in same physical state is called
a) Isomerism   b) Allotropy
c) Catenation   d) Crystallinity

2. Number of free electron(s) in each carbon of graphite is
a) one    b) two
c) three   d) four

3. The carbon atoms in fullerene are arranged in mixed
a) Tetragon and Pentagon   b) Pentagon and Hexagon
c) Hexagon and Heptagon   d) Heptagon and Octagon

4. Carbon forms large number of organic compounds due to
a) Allotropy         b) Isomerism
c) Tetravalency   d) Catenation

5. Diamond is not a good conductor of electricity because
a) it is very hard                    b) it has no free electron
c) its structure is uniform   d) it is insoluble in water

6. Which of the following does not contain a double bond.
a) CO2    b) C2H4
c) HCl    d) O2

7. Which of the following is highly toxic?
a) Carbon dioxide          b) Carbon monoxide
c) Calcium carbonate    d) Sodium bicarbonate

8. Raagav brings his lunch every day to school in a plastic container which has resin code number 5. The container is made of
a) Polystyrene             b) PVC
c) Polypropylene   d) LDPE

9. Plastics made of Polycarbonate (PC) and Acrylonitrile Butadiene Styrene (ABS) are made of resin code
a) 2   b) 5
c) 6   d) 7

10. Which of the following plastic items are banned by the Government of Tamil Nadu as of 1st January2019?
a) Plastic sheets                 b) Plastic tea cups
c) Plastic water packets   d) All the above

11. Graphite is used as lubricant in machines because
a) it is good conductor of electricity.
b) it is made of slippery layers and has high melting point.
c) it has high density
d) it is strong and soft

12. The lead pencil contains
a) graphite   b) diamond
c) lead               d) charcoal

13. Graphene is one atom thick layer of carbon obtained from
a) Diamond      b) Fullerene
c) Graphite   d) Gas Carbon

14. Plastic resin codes are shown as three chasing arrows in a with a number in the middle or letters (an acronym of that plastic type)
a) Logo       b) Recycling symbol
c) Square   d) Triangle

15. The legal measures to prevent plastic pollution come under the Protection Act 1988.
a) Forest                     b) Wildlife
c) Environment   d) Human Rights

II. Fill in the blanks:

1. Antoine Lavoisier named carbon.
2. Buckminster Fullerene contains 60 carbon atoms.
3. Compounds with the same molecular formula and different structural formula are known as Isomers.
4. Different methods of formation of carbon are the main reason for its catenation.
5. There are seven plastic resin codes.

III. Match the following:

1. Alkyne              a) Bucky Ball
2. Andre Geim    b) Oxidation
3. C60                   c) Graphene
4. Thermocol       d) Triple bond
5. Burning             e) Polystyrene
Ans: 1- d; 2- c; 3-a; 4- e; 5-b.

IV. Answer the following by rearranging the jumbled letters:

1. It is the hardest allotrope of carbon. Mnodaid    Ans: diamond
2. Organic compounds having double bond between carbon atoms are Knelaes   Ans: alkenes
3. Reaction of carbon with oxygen gives Osdiexs   Ans: oxides
4. In this molecule, carbon is attached with four hydrogen atoms. Emathen   Ans: methane
5. Carbon combines with other elements through bond. Inaocvet   Ans: covalent
6. It is used as gun powder. Ocahrcla Ans: charcoal
7. Plastics made of are represented by resin code #6. Sytlopynere Ans: polystyrene
8. One-time use plastics are also known as plastic. Awyrhotwa Ans: throwaway
9. One-time use plastics cause damage. Imvomenialne Ans: environmental
10. Expanded polystyrene is commercially know as Mthreolco Ans: thermocol

V. Short Questions & Answers:

1. How many valence electrons are there in carbon?
There are four valence electrons in carbon.

2. Who is called ‘Father of Modern Organic Chemistry’?
Friedrich Wohler is called the ‘Father of Modern Organic Chemistry’.

3. Which three resin codes are unsafe?
Resin code #3
Resin code #6
Resin code #7

4. Differentiate graphite and diamond.

5. What are saturated and unsaturated compounds called?
Saturated compounds are compounds which contain carbon-carbon and carbon-hydrogen single bonds. Unsaturated compounds contain carbon-carbon double bonds or triple bonds.

6. Carbon does not form Ionic compounds. Why?
Carbon has the tendency to share its four electron with other atoms to complete its octet. This is called tetravalency. Thus carbon can form four covalent bond with other elements. Hence it does not form Ionic compounds.
Carbon possesses a net charge which is due to strong electro negative atom present in compound.

7. What is the valency of carbon in carbon monoxide?
The valency of carbon in carbon monoxide is two.

8. Why are one-time use and throw away plastics harmful?
One-time use and throwaway plastics cause short and long term environmental damage. Half of all the plastics made today is used for throw away plastic items. These plastics block drains and pollute water bodies. One time use plastic causes health problems for humans, plants and animals.

9. Why does carbon exist mostly in combined state?
Carbon is found in both Free State and combined state. There are millions of organic compounds of carbon. As the same time carbon is constituent of many inorganic compounds. More than 5 million compounds are known at present. The number of carbon compounds alone is more than number of compounds of all the elements taken together because carbon has some unique feature such as catenation, Tetra valency, Multiple bonds, isomerism, Allotropy.

10. When a carbon fuel burns in less aerated room, it is dangerous to stay there, Why?
When carbon fuels undergo incomplete combustion (insufficient supply of oxygen), it results in the formation of carbon monoxide. It is released into the atmosphere from various sources like vehicle fuels, domestic fuels, industries, furnaces etc. Cigarette smoking also is a source of carbon monoxide.
When carbon fuel burns in less aerated room it releases carbon monoxide. This carbon monoxide is a toxic gas. It enters human body through breathing and affects the function of hemoglobin. Carbon monoxide displaces oxygen from hemoglobin and it stops its function leading to death.

11. Explain how dioxins are formed, which plastic type they are linked to and why they are harmful to humans.
Dioxins are formed by burning industries and domestic plastic wastes. They are linked to #3 PVC plastics.
In human beings they cause productive and developmental problems. They damage the immune system, interfere with hormones and also cause cancer.

12. Yugaa wants to buy a plastic water bottle. She goes to the shop and sees four different kinds of plastic bottles with resin code 1, 3, 5 and 7. Which one should she buy? Why?
She should buy plastic bottles with resin code #5 Name: Polypropylene
Code: PP
It is one of the safest plastics.

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