Samacheer Kalvi 9th Science Solutions Chapter 15 Pdf

Tamilnadu Board Samacheer Kalvi 9th Science Solutions Chapter 15: Tamilnadu State Board Solution Class 10 Science Chapter 15 – Carbon and its Compounds.

Samacheer Kalvi 9th Science Solutions Chapter 15: Overview

Board	Samacheer Kalvi
Class	9
Subject	Science
Chapter	15
Chapter Name	Carbon and its Compounds

Samacheer Kalvi 9th Science Solutions Chapter 15 Carbon and its Compounds

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

(d) Crystallinity

Ans: (b) Allotropy

Explanation: Because, allotropy is the property by which an element can exist in more than one form which have different physical properties but same chemical properties.

(2) Carbon forms large number of organic compounds due to

(a) Allotropy

(b) Isomerism

(d) Catenation

Ans: (d) Catenation

Explanation: Because, Catenation is the binding of an element with itself or with the other elements with covalent bonds to form open or closed chain compounds.

Carbon atoms links linearly and repeatedly with itself through covalent bonding to form linear chain, branched chain and ring structures.

Due to this property of carbon it has large number of organic compounds

(3) Nadine 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

(d) LDPE

Ans: (c) Polypropylene

Because, the plastic with resin code no. 5 is made with Polypropylene.

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

(a) 2

(b) 5

(d) 7

Ans: (d) 7

Explanation: Because, Plastics made of Polycarbonate (PC) and Acrylonitrile Butadiene Styrene (ABS) are made of resin code 7.

(5) Graphene is one atom thick layer of carbon obtained from

(a) Diamond

(b) Fullerene

(d) Gas carbon

Ans: (c) Graphite

Explanation: Because, grapheme is one atom thick layer of carbon obtained from graphite.

(6) The legal measures to prevent plastic pollution come under the _____________ Protection Act 1988.

(a) Forest

(b) Wildlife

(d) Human rights

Ans: (c) Environment

Explanation: Because,the legal measures to prevent plastic pollution come under the environment Protection Act 1988.

Fill in the blanks.

(1) _____________ named carbon.

Ans: Antoine Lavoisier named carbon.

(2) Buckminster Fullerene contains ______ carbon atoms.

Ans: Buckminster Fullerene contains 60 carbon atoms.

(3) Compounds with same molecular formula and different structural formula are known as ___________.

Ans:Compounds with same molecular formula and different structural formula are known as isomers.

(4) _______________ is a suitable solvent for sulphur.

Ans: Toluene is a suitable solvent for sulphur.

(5) There are ________ plastic resin codes.

Ans: There are 7 plastic resin codes.

III. Match the following.

Ans:

1) Alkyne: Triple bond

2) Andre Geim : Grapheme

3) C₆₀: Bucky Ball

4) Thermocol: Polystyrene

5) Combustion: Oxidation

Answer briefly.

(1) Differentiate graphite and diamond

Ans:

Allotropy is the property by which an element can exist in more than one form which have different physical properties but same chemical properties.

And the different forms of it are called as allotropes.

Carbon exist in three allotropic forms namely Diamond, Graphite and Fullerene.

The difference between Diamond and Graphite is as given below:

In diamond each Carbon has four covalent bonds whereas in graphite each Carbon has three covalent bonds.
Diamond is the hard, heavy and transparent allotropes of carbon. While graphite is soft, slippery to touch and opaque allotropes of carbon.
Diamond has tetrahedral units linked in three dimensions. While graphite has planar layers of hexagon units.
Diamond is the nonconductor of electricity but graphite is the good conductor of heat and electricity.

(2) Write all possible isomers of C4H10.

Ans:

Isomers are the molecules having same molecular formula but different structural formula.

The molecular formula C₄H₁₀is the molecular formula of Butane which is an alkane.

It has only two isomers that are n-butane and iso-butane as shown below.

Fig. isomers of Butane

(3) Carbon forms only covalent compounds. Why?

Ans:

The atomic no. of carbon is 6, with electronic configuration as 2, 4. That means it has electrons in its outermost orbit. According to Octet rule, carbon requires 4 extra electrons to attain the nearest Nobel gas electronic configuration. So Carbon has tendency to share its 4 electrons to other atoms by forming the covalent bonds.
This property of carbon is called as tetravalency. Thus, carbon can forms the four covalent bonds with the other four atoms in order to attain the nearest Nobel gas electronic configuration.
For example: in methane CH₄ carbon atom shares it’s 4 electrons with other 4 hydrogen atoms to form the four covalent bonds and complete it’s tetravalency.

(4) Define Allotropy.

Ans:

Allotropy is the property by which an element can exist in more than one form which are having different physical properties but same chemical properties.
The different forms of that elements are called as its allotropes.
Carbon exist in nature in its three allotropic forms namely Diamond, Graphite and Fullerene which are the crystalline forms of carbon

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

Ans:

Plastics are made from long chain organic compounds called polymer resins with chemical additives which gives them different properties.
One time use and thrown away plastics cause short and long term environmental damaging effects. Half of the all plastics made today is used for throwaway plastic items. This block drains and pollute water bodies. One time plastic use can cause health problems for human, animals and plants also.
Some of these are plastic carry bags, cups, plates, straws, water pouches, cutlery and plastic sheets used for food wrapping.
This all items requires very less time to make and we use them for short period and by using them one time, we throw them away. After throwaway they remains as it is up to 1000 years in environment causing plastic pollution for future generations.
That’s why government has given some rules to use plastic which protects the environment from plastic pollution.
So it is very harmful, the onetime use and throwaway of plastics in environment.

Answer in detail.

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

Ans:

Catenation is the binding of an element with itself or with the other elements with covalent bonds to form open or closed chain compounds.
Carbon atoms links linearly and repeatedly with itself through covalent bonding to form linear chain, branched chain and ring structures.
Due to this property of carbon it has large number of organic compounds.

For example: Starch and cellulose contains chains of hundreds of carbon atoms.

Fig. catenation in Carbon

2) What are the chemical reactions of carbon?

Ans:

Elemental carbon cannot reacts with other atoms or compound at room temperature and in limited at elevated temperatures also.

But, carbon compounds undergoes large no. of reactions even at room temperature.

1.) Oxidation i.e. reaction with oxygen:

Carbon combines with oxygen to form it’s oxides like carbon monoxide and carbon dioxide with the evolution of heat.

2C_s + O_2g = 2CO_g + heat

C_s + O_2g = CO_2g + heat

2.) Reaction with steam:

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

C_s + H₂O_g→ CO_g + H_2g

3.) Reaction with Sulphur:

Carbon reacts with Sculpture at high temperature to form its disulphide.

C_s + 2S_g = CS_2g

4.) Reaction with metals:

At elevated temperature carbon reacts with some metals like iron, tungsten, titanium etc.

Tungsten + Carbon = tungsten carbide

W + C = WC

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

Ans:

The resin code on the plastic shows that which type of polymer is used to make that plastic.

We have to dispose plastic safely and it can also be recycled, reused. But there are some plastics which we use one time only and then it will be thrown away which remain as it up to many years, and causes the pollution in environment or harms the human health also.

Different types of plastics are made from different polymers and they didn’t mix when we recycle them. For this reason we have to separate them well after use for recycling. To identify them easily resin codes are developed in 1988 which helps in recyclers in plastic sorting process.

There are some safer resin codes of plastic which are as given below:

Resin code 2 PEHD: This type of plastics are light in weight, strong and they are also recycled for further use.
Resin code 4 PELD, LLDPE: This type of plastics are soft and strong and they are flexible also.
Resin code 5 PP: This type of plastics are light in weight, waxy and hard. But they may be scratches easily.

Higher Order Thinking Skills

(1) Why do carbon exist mostly in combined state?

Ans:

The atomic no. of carbon is 6, with electronic configuration as 2, 4. That means it has electrons in its outermost orbit. According to Octet rule, carbon requires 4 extra electrons to attain the nearest Nobel gas electronic configuration. So Carbon has tendency to share its 4 electrons to other atoms by forming the covalent bonds.
This property of carbon is called as tetravalency. Thus, carbon can forms the four covalent bonds with the other four atoms in order to attain the nearest Nobel gas electronic configuration. And it exist mostly in combined state.

For example: in methane CH₄ carbon atom shares it’s 4 electrons with other 4 hydrogen atoms to form the four covalent bonds and complete it’s tetravalency.

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

Ans:

When a carbon fuel burns in less aerated room, the carbon fuel burns with the help of oxygen. Because, oxygen is an oxidizer which means it does not burns self but supports in the process of burning.
Hence, carbon monoxide is formed in that less aerated room.
When we take in the carbon monoxide through breathing, it mainly affects the function of hemoglobin in blood.
CO displaces the oxygen from hemoglobin, due to which we can’t get proper oxygen supply to our whole body and that cause the death.
For this reason a carbon fuel burns in less aerated room 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?

Ans:

The PVC Polyvinyl Chloride plastics are made up of heavy metals like cadmium and lead. Phthalates are the chemicals added in PVC which copy our hormones.

After burning of PVC it releases one of the most toxic chemical known to humans called dioxins.

Because, dioxins cause the problems to reproductive system and harms to development of body.

Also damages to immune system and interacts with hormones by causing cancer.

Hence, it is very harmful to humans. So PVC are suggested not to burn them.

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?

Ans:

Yugaa should buy the plastic bottle with resin code 5, because it is the safer resin code for plastic made from PP.

Since, other resin codes 1, 3 and 7 are the harmful resin codes which creates pollution in the environment.

So in order to be safe, Yugaa must buy plastic bottle with resin code 5 only.