9th Standard Syllabus & Materials
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Published on: 09/10/2019
Term 3 Carbon and its Compounds
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Questions + Answers key
Take MCQ Science Test1.
What can you do to prevent plastic pollution?
2.
| Type of bond | Example | Class of the compound |
| Single bond | - 1 - | Alkane |
| Double bond | \(H-\overset { \underset { | }{ H } }{ C } =\overset { \underset { | }{ H } }{ C } -H\) | - 2 - |
| - 3 - | - 4 - | Alkyne |
3.
How can you find resin code on plastic items?
4.
What is burning?
5.
What is tetravalency in carbon? Give example.
6.
Why are one-time use and throwaway plastics harmful?
7.
What is the valency of carbon in carbon monoxide?
8.
Carbon does not form ionic compounds. Why?
9.
What are saturated and unsaturated compounds called?
10.
Differentiate graphite and diamond.
1.
1. By sharing my scientific knowledge on plastics and their effects with my parents relatives and friends to make them aware of plastic pollution .
2. I can help by teaching them how to avoid harmful plastics by searching for the resin code.
3. By educating them about the new rules and how important is to stop one-time use plastics.
2.
1. \(H-\overset { \underset { | }{ H } }{ \underset { \overset { | }{ H } }{ C } } -H\)
2. Alkene
3. Triple bond
4. H - C ☰ C - H (Ethyne)
3.
The secret resin codes are shown as three chasing arrows in a triangle. There is a number in the middle or letters under the triangle which is an acronym of that plastic type. It can be found on the label or bottom of a plastic item.
4.
Organic compounds like hydrocarbon undergo oxidation to form oxides and steam with evolution of heat and flame. This is called burning.
CH4(g)+ 2O2(g) ➝ CO2(g)+ 2H2O(g) + heat
5.
Carbon has the tendency to share its four electrons with other atoms to complete its octet. This is called tetravalency.
Eg:- In methane, carbon atom shares its four valence electrons with four hydrogen atoms to form four covalent bonds and hence tetravalent.

6.
1. Use and throwaway plastics cause short and long term environmental damage.
2. Half of all the plastic items made today is used for throwaway plastic items.
3. They block drains and pollute water bodies .
4. One-time use plastic causes health problems for humans, plants and animals.
5. If these items are thrown away they can stay in our environment for over 1000 years causing plastic pollution for future generations.
6. Some examples are plastic carry bags, cups, plates, straws, water pouches etc.
7.
In carbon monoxide, the electron pairs of oxygen gets delocalized between C and O. So without another oxygen atom, the structure becomes stable as oxygen shares its lone pair with carbon.

i) Thus in carbon monoxide, one electron of tetravalent carbon forms sigma and other electron forms pi bond with oxygen.
ii) Then one lone pair of oxygen is shared between C and O, so that C has complete octet.
iii) Thus two unbonded electrons of C are available, so valency is 2.
Thus valency of carbon in CO is 2.
8.
1. Covalent bonding is the sharing of electron between atoms. This type of bonding occurs between two atoms of the same element.
2. To form Ionic compounds carbon must gain four electrons forming C4- anions but it would be difficult for its nucleus with six protons to hold onto ten electrons .
3. It could lose four electrons to form C4+ cations, but it would require a large amount of energy to remove four electrons .
4. These two conditions are highly unfavourable. Therefore carbon molecules share their four valence electrons through single, double, and triple bonds so that each atom can achieve noble gas configuration.
9.
| Saturated Compounds | Unsaturated Compounds |
| i) Saturated compounds are organic compounds that have only carbon - carbon single bonds. | Unsaturated compounds are organic compounds containing at least one double bond or triple bond between carbon atoms. |
| ii) Less reactive | Highly reactive |
| iii) More stable | Less stable |
| iv) Do not undergo polymerisation | undergo polymerisation |
| v) More stable | Less stable |
| vi) Includes Alkanes | Includes Alkenes, Alkynes and aromatic compounds. |
10.
| Diamond | Graphite |
| i) Each carbon has four covalent bonds | Each carbon has three covalent bonds |
| ii) Hard, heavy and transparent | Soft, slippery to touch and opaque |
| iii) It has tetrahedral units linked in three dimension | It has planar layers of hexagon units |
| iv) It is a non-conductor of heat and electricity | It is a conductor of heat and electricity |
9th Standard Syllabus & Materials
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Tamilnadu Stateboard 9th Standard Subjects
Tamilnadu Stateboard Standards