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9th Science Guide Unit 15 Carbon and its Compounds

9th Science Guide Unit 15 Carbon and its Compounds

9th Std Science Lesson 15 Carbon and its Compounds – English Medium Guide

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9th Science Guide Unit 15 Carbon and its Compounds

I. Choose the Correct Answer

1. A phenomenon in which an element exists in different modification in the same physical state is called

  1. Isomerism
  2. Allotropy
  3. Catenation
  4. Crystallinity

2. Number of free electron(s) in each carbon of graphite is

  1. one
  2. Two
  3. Three
  4. Four

3. The carbon atoms in fullerene are arranged in mixed

  1. Tetragon and Pentagon
  2. Pentagon and Hexagon
  3. Hexagon and Heptagon
  4. Heptagon and Octagon

4. Carbon forms large number of organic compounds due to

  1. Allotropy
  2. Isomerism
  3. Tetravalency
  4. Catenation

5. Diamond is not a good conductor of electricity because

  1. it is very hard
  2. it has no free electron
  3. its structure is uniform
  4. it is insoluble in water

6. Which of the following does not contain double bond

  1. CO2
  2. C2H4
  3. HCl
  4. O2

7. Which of the following is highly toxic?

  1. Carbon dioxide
  2. Carbon monoxide
  3. Calcium carbonate
  4. 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

  1. Polystyrene
  2. PVC
  3. Polypropylene
  4. LDPE

9 Plastics made of Polycarbonate (PC) and Acrylonitrile Butadiene Styrene (ABS) are made of resin code _______

  1. 2
  2. 5
  3. 6
  4. 7

10. Which of the following plastic items are banned by the Government of Tamil Nadu as of 1st January 2019?

  1. Plastic sheets
  2. Plastic tea cups
  3. Plastic water packets
  4. All the above

11. Graphite is used as lubricant in machines because

  1. it is good conductor of electricity
  2. it is made of slippery layers and has high melting point
  3. it has high density
  4. it is strong and soft

12. The lead pencil contains

  1. Graphite
  2. Diamond
  3. Lead
  4. Charcoal

13. Graphene is one atom thick layer of carbon obtained from

  1. Diamond
  2. Fullerene
  3. Graphite
  4. 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).

  1. Logo
  2. Recycling symbol
  3. Square
  4. Triangle

15. The legal measures to prevent plastic pollution come under the ______ Protection Act 1988.

  1. Forest
  2. Wildlife
  3. Environment
  4. Human Rights

II. Fill in the Blanks

  1. _____________ named carbon. Ans : Antoine Lavoisier
  2. Buckminster Fullerene contains ______ carbon atoms. NAns : 60
  3. Compounds with same molecular formula and different structural formula are knows as ___________. Ans : Isomers
  4. Different methods of formation of carbon is the main reason for its _______________.

Ans : allotropes

  1. There are ________ plastic resin codes.

Ans : 7

III. Match the following.

  1. Alkyne – Bucky Ball
  2. Andre Geim – Oxidation
  3. C60 – Graphene
  4. Thermocol – Triple bond
  5. Burning – Polystyrene

Ans: 1 – D, 2 – C, 3 – A, 4 – E, 5 – B

IV. Answer in brief.

1. Differentiate graphite and diamond



1. Each carbon has four covalent bonds.

Each carbon has three covalent bonds.

2. Hard, heavy, and transparent.

Soft, slippery to touch and opaque.

3. It has tetrahedral units linked in three dimension.

It has planar layers of hexagon units.

4. It is non-conductor of heat and electricity.

It is conductor of heat and electricity.

2. What are saturated and unsaturated compounds called?

Organic compounds containing carbon. Carbon single bonds are known as saturated compounds. Organic compounds containing one (or) more double (or) triple bonds are known as unsaturated compounds

3. Carbon do not form ionic compounds. Why?

It has four electrons in its outermost orbit. According to Octet Rule, carbon requires four electrons to attain nearest noble gas (Neon) electronic confi guration. So carbon has the tendency to share its four electrons with other atoms to complete its octet. So carbon do not form ionic compounds.

4. What is the valency of carbon in carbon monoxide?

The valency of carbon in carbon monoxide is two.

5. Why are one-time use and throwaway plastics harmful?

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

9th Science Guide Unit 15 Carbon and its Compounds

V. Answer in detail.

1. What is catenation? How does carbon form catenated compounds?

Catenation is binding of an element to itself or with other elements through covalent bonds to form open chain or closed chain compounds. Carbon is the most common element which undergoes catenation and forms long chain compounds. Carbon atom links repeatedly to itself through covalent bond to form linear chain, branched chain or ring structure.

This property of carbon itself is the reason for the presence of large number of organic carbon compounds. So organic chemistry essentially deals with catenated carbon compounds.

2. What are the chemical reactions of carbon?

Oxidation – (Reaction with oxygen)

Carbon combines with oxygen to form its oxides like carbon monoxide (CO) and carbon dioxide (CO2) with evolution of heat.

2C(s) + O2(g)) → 2 CO(g)+ heat

C(s) + O2(g)→ C O2(g)+ heat

Reaction with steam

Carbon reacts with steam to form carbon monoxide and hydrogen. This mixture is called water gas.

C(s) + H2O(g) → C O(g) + H2(g)

Reaction with sulphur

With sulphur, carbon forms its disulphide at high temperature.

C(g) + S(g) → C S2(g)

Reaction with metals

At elevated temperatures, carbon reacts with some metals like iron, tungsten, Titanium, etc. to form their carbides.

W(s) + C(g) → WC(s)

3. Name the three safer resin codes of plastics   and describe their features.


1. Why do carbon exist mostly in combined state?

Carbon exist mostly in combined state because of catenation,Tetra valency and formation of multiple bonds

2. When a carbon fuel burns in less aerated room, it is dangerous to stay there. Why?

When a carbon fuel burns in less aerated room, it produces carbon monoxide , which is highly toxic because it affects the oxygen carrying capacity of it is dangerous to stay there

3. Explain how dioxins are formed, which plastic type they are linked to and why they are harmful to humans.

Burning of PVC releases dioxins.Dioxins are very toxic to humans, because they cause skin, liver problems and affect nervous, endocrine and reproductive systems.

4. Yugaa wants to buy a plastic water bottle. She goes to the shop and sees four different kinds of plastic bottles with resin codes 1, 3, 5 and 7. Which one should she buy? Why?

Resin cods 1,3,7 are harmful plastics but resin code 5 is PP(poly propylene). It is a safer plastic. Therefore she should buy the plastic bottle with resin code 5.


VII.Answer the following by rearranging the jumbled letters.

1. It is the hardest allotrope of carbon.


Ans : diamond

2. Organic compounds having double bond between carbon atoms are


Ans : alkenes

3. Reaction of carbon with oxygen gives


Ans : oxides

4. In this molecule, carbon is attached with four hydrogen atoms.


Ans : methane

5. Carbon combines with other elements through _______ bond.


Ans : Covalent

6. It is used as gun powder.


Ans : Charcoal

7. Plastics made of _________ are represented by resin code #6.


Ans : polystyrene

8. One-time use plastics are also known as ____________ plastics.


Ans : throwaway

9. One-time use plastics cause ____________ damage.


Ans : environment

10. Expanded polystyrene is commercially known as


Ans : thermocol

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