CLASS-9 SUBJECT SCIENCE CHAPTER-3 ATOMS AND MOLECULES

 EVENTS CONVENT HIGH SCHOOL

08/11/2021      CLASS- 9   SESSION 2021-22
SUBJECT :  SCIENCE

CHAPTER-3
ATOMS AND MOLECULES

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Question 1. In a reaction 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium ethanoate. Show that these observations are in agreement with the law of conservation of mass carbonate.
Answer.

Class 9 Science NCERT Textbook Page 32
Question 1. In a reaction 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium etkanoate. Show that these observations are in agreement with the law of conservation of mass carbonate.
Answer:

Question 2. Hydrogen and oxygen combine in the ratio of 1 : 8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
Answer: Ratio of H : O by mass in water is:
Hydrogen : Oxygen —> H2O
∴ 1 : 8 = 3 : x
x = 8 x 3
x = 24 g
∴ 24 g of oxygen gas would be required to react completely with 3 g of hydrogen gas.

Question 3. Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass?
Answer: The postulate of Dalton’s atomic theory that is the result of the law of conservation of mass is—the relative number and kinds of atoms are constant in a given compound. Atoms cannot be created nor destroyed in a chemical reaction.

Question 4. Which postulate of Dalton’s atomic theory can explain the law of definite proportions?
Answer: The relative number and kinds of atoms are constant in a given compound.

Class 9 Science NCERT Textbook Page 35
Question 1. Define the atomic mass unit.
Answer: One atomic mass unit is equal to exactly one-twelfth (1/12th) the mass of one atom of carbon-12. The relative atomic masses of all elements have been found with respect to an atom of carbon-12.

Question 2. Why is it not possible to see an atom with naked eyes?
Answer: Atom is too small to be seen with naked eyes. It is measured in nanometres.
1 m = 109 nm

NCERT Textbook Questions – Page 39
Question 1. Write down the formulae of
(i) Sodium oxide
(ii) Aluminium chloride
(iii) Sodium sulphide
(iv) Magnesium hydroxide
Answer: The formulae are

Question 2. What is meant by the term chemical formula?
Answer: The chemical formula of the compound is a symbolic representation of its composition, e.g., chemical formula of sodium chloride is NaCl.

Question 3. How many atoms are present in a
(i) H2S molecule and
(ii) P043- ion?
Answer: (i) H2S —> 3 atoms are present
(ii) P043- —> 5 atoms are present

NCERT Textbook Questions – Page 40
Question 1. Calculate the molecular masses of H2, O2, Cl2, C02, CH4, C2H2,NH3, CH3OH.
Answer: The molecular masses are:

Question 2.Calculate the formula unit masses of ZnO, Na2O, K2C03, given atomic masses of Zn = 65 u, Na = 23 u, K = 39 u, C = 12 u, and O = 16 u.
Answer: The formula unit mass of
(i) ZnO = 65 u + 16 u = 81 u
(ii) Na2O = (23 u x 2) + 16 u = 46 u + 16 u = 62 u
(iii) K2C03 = (39 u x 2) + 12 u + 16 u x 3
= 78 u + 12 u + 48 u = 138 u

Class 9 Science NCERT Textbook Page 42
Question 1. If one mole of carbon atoms weigh 12 grams, what is the mass (in grams) of 1 atom of carbon?
Answer:

Question 2. Which has more number of atoms, 100 grams of sodium or 100 grams of iron (given atomic mass of Na = 23 u, Fe = 56 u)?
Answer:

Questions From NCERT Textbook for Class 9 Science

Question 1. A 0.24 g sample of compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen. Calculate the percentage composition of the compound by weight.
Answer: Boron and oxygen compound —> Boron + Oxygen
0.24 g —> 0.096 g + 0.144 g

Question 2. When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen? Which law of chemical combination will govern your answer?
Answer: The reaction of burning of carbon in oxygen may be written as:

It shows that 12 g of carbon bums in 32 g oxygen to form 44 g of carbon dioxide. Therefore 3 g of carbon reacts with 8 g of oxygen to form 11 g of carbon dioxide. It is given that 3.0 g of carbon is burnt with 8 g of oxygen to produce 11.0 g of CO2. Consequently 11.0 g of carbon dioxide will be formed when 3.0 g of C is burnt in 50 g of oxygen consuming 8 g of oxygen, leaving behind 50 – 8 = 42 g of O2. The answer governs the law of constant proportion.

Question 3. What are poly atomic ions? Give examples.
Answer: The ions which contain more than one atoms (same kind or may be of different kind) and behave as a single unit are called polyatomic ions e.g., OH–, SO42-, CO32-.

Question 4. Write the chemical formulae of the following:
(a) Magnesium chloride
(b) Calcium oxide
(c) Copper nitrate
(d) Aluminium chloride
(e) Calcium carbonate.
Answer: (a) Magnesium chloride
Symbol —> Mg Cl
Change —> +2 -1
Formula —> MgCl2
(b) Calcium oxide
Symbol —> Ca O
Charge —> +2 -2
Formula —> CaO
(c) Copper nitrate
Symbol —> Cu NO
Change +2 -1
Formula -4 CU(N03)2
(d) Aluminium chloride
Symbol —> Al Cl
Change —> +3 -1
Formula —> AlCl3
(d) Calcium carbonate
Symbol —> Ca CO3
Change —> +2 -2
Formula —> CaC03

CLASS-9 SUBJECT-SOCIAL SCIENCE CHAPTER-3 DRAINAGE

 EVENTS CONVENT HIGH SCHOOL

08/11/2021      CLASS- 9   SESSION 2021-22
SUBJECT :  SOCIAL SCIENCE

CHAPTER-3
DRAINAGE

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Question-1 What is meant by the water divide? Give an example.
Solution:
Any elevated area, such as a mountain or upland, separates two drainage basins. Such upland is known as the water divide. Ambala is located on the water divide between the Indus and the Ganga river systems.

Question-2 Which is the largest river basin in India?
Solution:
The Ganga basin is the largest basin in India.

Question-3
Where do the rivers Indus and Ganga have their origin?
Solution:
The headwaters of the Ganga called the ‘Bhagirathi’ is fed by the Gangotri Glacier and joined by the Alaknanda at Devaprayag in Uttaranchal. At Haridwar, the Ganga emerges from the mountains on to the plains. The Indus flows through Baltistan and Gilgit and emerges from the mountains at Attock.

Question-4
Name the two headstreams of the Ganga. Where do they meet to form the Ganga?
Solution:
Alakananda and Bhagirathi are the two headstreams of the Ganga. They meet at Devaprayag.

Question-5
Why does the Brahmaputra in its Tibetan part have less silt, despite a longer course?
Solution:
The Brahmaputra river, which is known as Tsangpo in Tibet, receives a very little volume of water in Tibet so it has less silt there. On the other hand, this very river when enters India it passes through such a region which receives heavy rainfall. As such in India, it carries a large volume of water and a larger amount of silt.

Question-6
Which two Peninsular rivers flow through trough?
Solution:
Narmada and Tapi are the two Peninsular rivers, which flow through the trough.

Question-7
Discuss the significant difference between the Himalayan and the Peninsular rivers.
Solution:
The Himalayan Rivers The Peninsular or Deccan Rivers
1. The Himalayan rivers rise in the snow-covered mountains as such they flow throughout the year. The mountains in which the Deccan rivers rise are not snow-covered. Hence they dry up in summer.

2. The Himalayan rivers flow in leveled Northern Plains. Therefore, they are quite useful for navigation and irrigation. The Peninsular rivers flow on the uneven rocky surface. Therefore they are neither navigable nor useful for irrigation.

3. The Himalayan rivers bring with them fertile alluvium which they deposit in the Indo-Gangetic Plains. The Peninsular rivers do not bring with them enough alluvium. As the current is swift so the deposition activity is negligible.

4. Canals have been dug to use the water of these rivers for irrigation. As the terrain is rocky and the banks of these rivers are high, canals cannot be dug. However, dams are built to store the floodwater for irrigation with the help of small channels.

5. Many important towns and centres of trade are situated on the banks of these rivers. Very few important towns and centres of trade are situated on the banks of these rivers.

6. The porous soil absorbs a lot of water, which is later on used as groundwater by digging wells and tube wells for domestic and irrigation purposes. The rocky soil does not absorb any water. Hence no wells can be dug. All the water flows down the sea at one and the same time.

Question-8
Compare the east-flowing and the west-flowing rivers of the Peninsular plateau.
Solution:
East Flowing Rivers
The Mahanadi, the Godavari, the Krishna, and the Kaveri are the main east flowing rivers of Peninsular India. These rivers drain in the Bay of Bengal. These rivers make deltas at their mouth

West Flowing Rivers.
These rivers have a developed tributary system. Their tributaries are comparatively large in size. These rivers flow through not very deep channels.

The Narmada and the Tapi are the main west-flowing rivers of Peninsular India. These rivers drain in the Arabian Sea. These rivers enter the sea through estuaries. These rivers are devoid of developed tributary system. Their tributaries are quite small in size. These rivers flow in a trough or a funnel-like narrow but deep channel.

CLASS-8 SUBJECT SCIENCE CHAPTER-5 COAL AND PETROLEUM

 EVENTS CONVENT HIGH SCHOOL

08/11/2021      CLASS- 8   SESSION 2021-22
SUBJECT :  SCIENCE

CHAPTER-5
COAL AND PETROLEUM

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Question 1.What are the advantages of using CNG and LPG as fuels?

Answer:
The advantages of using CNG and LPG as fuels are:

• They burn with a smokeless flame and so does not cause any pollution.
• They leave no ash on burning.
• They are easy to handle and convenient to store.

Question 2.Name the petroleum product used for surfacing of roads.
Answer:
Bitumen

Question 3.Describe how coal is formed from dead vegetation. What is this process called?
Answer:
Millions of years ago, trees, plants, ferns and forests got buried below the rocks, soil and sand due to natural processes like flooding, earthquake, etc. Slowly, as more soil deposited over them, they were compressed. This led to the conditions of high pressure and heat. These conditions along with the anaerobic conditions turned the carbon-enriched organic matter of wood into coal.
This slow process of conversion of wood into coal is called carbonisation.

Question 4.Fill in the blanks.
(a) Fossils fuels are ____ , ____ and ____
(b) Process of separation of different constituents from petroleum is called ______
(c) Least polluting fuel for vehicle is ______
Answer:
(a) coal, petroleum, natural gas
(b) refining
(c) CNG

Question 5.Tick True/False against the following statements.
(a) Fossil fuels can be made in the laboratory.
(b) CNG is more polluting fuel than petrol.
(c) Coke is an almost pure form of carbon.
(d) Coal tar is a mixture of various substances.
(e) Kerosene is not a fossil fuel.
Answer:
(a) False
(b) False
(c) True
(d) True
(e) False

Question 6.Explain why fossil fuels are exhaustible natural resources.
Answer:
Fossil fuels take millions of years to be formed. They are limited in nature and cannot be replenished easily, once consumed. Hence, they are considered as exhaustible natural resources.

Question 7.Describe the characteristics and uses of coke.
Answer:
Characteristics of coke: Coke is 98% pure carbon. It is a tough, porous and black substance. It pro-duces a very little smoke.
Uses of coke: Coke is very useful as fuel. It is a good reducing agent. It is widely used in metallurgical processes to reduce metals from their oxides. It is used for producing water gas.

Question 8.Explain the process of the formation of petroleum.
Answer:
Petroleum is formed by the burial of aquatic plants and animals below the sea bed. The marine animals and plants died thousands of years ago and settled down in the bottom of sea. In anaerobic conditions, microorganisms decompose this organic matter. Due to high pressure and heat, the dead remains of tiny plants and animals were slowly converted into petroleum.

Question 9.The following table shows the total power shortage in India from 2004-2010. Show the data in the form of a graph. Piet shortage percentage for the years on the y-axis and the year on the x-axis.

S. No.	Year	Shortage (%)
1	2004	7.8
2	2005	8.6
3	2006	9.0
4	2007	9.5
5	2008	9.9
6	2009	11.2
7	2010	10.0

Answer: