Lakhmir Singh Manjit Kaur Chemistry 2020 2021 for Class 9 Science Chapter 6 - Model Test Paper 1

Answer:

Rabi crops are sown from November to the month of April.

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The secondary wall of sclerenchyma is composed of lignin.

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Speed is a scalar quantity as it can be described by the only magnitude, we do not need direction while describing it.

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When the prongs of a sound producing tuning fork touch the surface of the water in a beaker, then we would see disturbances produced in the water in the form of ripples and waves. This shows that they vibrate.

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A primitive organism has a relatively simpler body design and structure. The body design of these organisms have not changed since their evolution. A typical example of primitive organism is an Amoeba. Advanced organisms, on the other hand, have complex body design and an advanced structural organization. An example of advanced organism is Homo sapiens.

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Answer:

Air is a mixture and water is a compound because:

1. Air contains different gases mixed together, which do not react to form any new compound. Whereas water is formed due to the chemical reaction between hydrogen and oxygen.

2. Air has a variable composition of its constituents, which depends on place to place. Whereas constituents of water i.e. hydrogen and oxygen are always found in a fixed ratio.

3. Air shows the properties of its constituents but the properties of water are entirely different than its constituents i.e. hydrogen and oxygen.

Answer:

$\underset{6 \mathrm{g}}{2{\mathrm{CH}}_3\mathrm{COOH}}+\underset{5.3 \mathrm{g} }{{\mathrm{Na}}_2{\mathrm{CO}}_3}\to 2\underset{8.2 \mathrm{g}}{{\mathrm{CH}}_3\mathrm{COONa}}+\underset{2.2 \mathrm{g}}{{\mathrm{CO}}_2}+\underset{0.9 \mathrm{g}}{{\mathrm{H}}_2\mathrm{O}}$

Total mass of reactants = 6 g + 5.3 g = 11.3 g
Total mass of products = 8.2 g + 2.2 g + 0.9 g = 11.3 g

The total mass of the reactants = Total mass of the products.

So, from this, we can verify the law of conservation of mass.

Answer:

In the given equation: p = m × v, 'p' is the momentum and 'm' and 'v' are the mass and velocity respectively.

This relation shows that the momentum of a body is given by the product of its mass and velocity.
 

Answer:

The gravitational force between two bodies of masses m₁ and m₂ separated by the distance r is given by, $F=\mathrm{G}\frac{m_1{m}_2}{r^2}$

Mass of the earth = 6 × 10²⁴ kg
Mass of the moon = 7.4 ×10²² kg
Distance between the earth and the moon = 3.84 × 10⁵ km
G = 6.7 × 10⁻¹¹ Nm² kg⁻²

Hence, the gravitational force between the earth and the moon,

 $$\begin{gathered} F=6.67\times {10}^{-11} {\mathrm{Nm}}^2{\mathrm{kg}}^{-2 }\times \frac{6\times {10}^{24} \mathrm{kg} \times 7.4\times {10}^{22 }\mathrm{kg}}{(3.84\times {10}^8 \mathrm{m}{)}^2} \\ \Rightarrow F\mathit{=}2.08\times {10}^{20} \mathrm{N} \end{gathered}$$
 

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(a) A man climbing a hill posses only potential energy by virtue of his height with respect to the ground.

(b) An aeroplane flies at a great height from the ground with a super high speed, so we can say that a flying aeroplane has both the potential and kinetic energies.

(c) A bird running on the ground has only kinetic energy because of its motion. 

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A cell is considered as the structural unit of life because cell constitutes the basic structure of living organisms. Every living organism and life form is made up of cells. Cells are also defined as the functional unit of life because most of the fundamental and life processes required for life are performed by cells. The metabolic reactions performed by cells forms the basis for all life processes. Thus, cells form the basic structural and functional unit of life.

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The differences between proiferan and coelentrate animals are as follows:
 

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Symptoms refer to a set of collective indications, which can be used to ascertain a particular disease. These generally appear as functional and structural changes in the body or a part of the body. Symptoms serve as a clue for a physician to identify the associated disease. Some of the examples of symptoms are as follows:
1. Jaundice is characterised by the symptoms of fever and yellowish coloration of skin.
2. Constipation, diarrhoea, abdominal pain and head ache are the symptoms associated with typhoid.

Answer:

The different causes of water pollution are as follows:
1. The dumping of sewage and household wastes into water bodies is a major reason for water pollution.
2. Industrial waste, which is discharged from factories and processing plants also contributes to water pollution.
3. Agriculture runoff can introduce fertilizers and pesticides into the water, which leads to water pollution.

Water pollution can be reduced by proper waste disposal, minimising agricultural runoff and bathing or washing of clothes in rivers should be avoided.

Answer:

(a) A mixture is a combination of two or more substances, which do not react with each other. Examples: sugar and water, sugar and sand, etc.

(b) (i) Homogenous mixtures: When two or more substances combine physically in a fixed ratio or a uniform composition, it is known as a homogeneous mixture. The homogenous mixture has no visible boundaries of separation. For e.g. Salt and water, sugar and water, etc.

(ii) Heterogeneous mixtures: When two or more substances combine in a non-uniform proportion, it is known as a heterogeneous mixture. It has visible boundaries of separation. For e.g. sand and water, oil and water, etc.
 

Answer:

(a) Thomson's model of an atom is similar to the model of plum pudding or watermelon. He said that the positive charge in an atom is spread all over like the red edible part of the watermelon. Also, electrons are embedded in the positively charged sphere like the seeds in the watermelon.

Explanation of Thomson' model:
(i) An atom consists of a positively charged sphere with electrons embedded in it.
(ii) The negative and positive charges present inside an atom are equal in magnitude. Therefore, an atom as a whole is electrically neutral.

Thomson only explained about electrons and protons, he did not take neutrons into consideration.

(b) Mass number of element = 18
Number of electrons = 7

For an atom, number of electrons = number of protons

Number of protons = number electrons = 7

Number of neutrons = (Mass number)$-$(number of protons)
Number of neutrons = 18$-$7
Number of neutrons = 11

The atomic number of an element is defined as the number of protons present. Therefore, the atomic number of the given element is 7.

Answer:

(a) Distance covered by the scooterist = 3 km = 3$\times$10⁵ cm

Time taken = 5 minutes = 300 seconds

Speed = $\frac{\mathrm{Distance}}{\mathrm{Time}}=\frac{3\times {10}^5 \mathrm{cm}}{300 \mathrm{s}}=1000 \mathrm{cm}/\mathrm{s}$

(b) Distance covered by the scooterist = 3 km = 3$\times$10³ m

Time taken = 5 minutes = 300 seconds

Speed = $\frac{\mathrm{Distance}}{\mathrm{Time}}=\frac{3\times {10}^3 \mathrm{cm}}{300 \mathrm{s}}=10 \mathrm{m}/\mathrm{s}$

(c)  Distance covered by the scooterist = 3 km 

Time taken = 5 minutes = $\frac{5}{60} \mathrm{hours}$

Speed = $\frac{\mathrm{Distance}}{\mathrm{Time}}=\frac{3 \mathrm{km}}{{\displaystyle \frac{5}{60}}\mathrm{h}}=36 \mathrm{km}/\mathrm{h}$

Answer:

(a) Work is said to be done when an object is displaced in the direction of applied force.  Work, $W=F\times s$ (Where 'F' is the applied force and 's' is the displacement in the direction of the force)

When a body moves against gravity, work is done by the body against the force of gravity. Let the body moves up a height of 'h' against the gravity, then work done by the body = $F\times s=\left(mg\right)\times h=mgh$ (Where 'm' is the mass, 'g' is acceleration due to gravity)

(b) According to relation work done = $\mathrm{Force}\times \mathrm{Displacement}=2 \mathrm{N}\times (10\times {10}^{-2}) \mathrm{m}=0.2 \mathrm{J}$

Hence, the work done by the given force is 0.2 J.

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The differences between fertilizer and manure have been summarised as follows:

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The fluid mosaic model of the plasma membrane can be represented as follows:


Figure.1. Fluid mosaic model of plasma membrane.

The fluid mosaic model is used to describe the structure of the plasma membrane. This model was proposed by Nicolson and Singer in 1972. This model suggests that the plasma membrane is composed of lipids and proteins primarily. However, small amounts of carbohydrates can also be found in the plasma membrane. The proteins of the plasma membrane can be integral or peripheral membrane proteins. These proteins   move through the lipid bilayer, which gives plasma membrane a typical fluidic nature. 
 

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When we place potassium permanganate crystals into the water, it's purple colour spreads throughout the water. This shows the diffusion of potassium permanganate in the water. Potassium permanganate has tiny particles, which get into the space between the water molecules. That's how its purple colour spreads throughout the water.

Answer:

Mass number of atom = 27
Number of neutrons = 14
Number of protons = Mass number$-$Number of neutrons
Number of protons = 27$-$14
Number of protons = 13

As the number of protons = Number of electrons
So, Number of electrons = 13
But the element has 3 positive(+3) charge that means this element has the deficiency of 3 electrons.
So, Number of electrons = 13$-$3 =10

Hence, the number of electrons in the given ion is 10.

Answer:

When a body is thrown up, it's velocity goes on decreasing, but its potential energy goes on increasing. The kinetic energy of the body gradually changes into the potential energy of the body as soon as it goes up above the ground. At the highest point, the velocity of the body becomes zero and all of the kinetic energy gets converted into potential energy. 

Answer:

(i) Murrah is a breed of buffalo, which originally belongs to Punjab and Haryana. This breed is characterised by large body size and short-curved horns.

(ii) The advantages of keeping Murrah buffaloes in diary are as follows:
1. These buffaloes can produce a large amount of milk during their lactation period. Typically 1800-2500 llitres of milk can be produced by these buffaloes.
2. These buffaloes are disease resistant.

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The immune system is essential for health because of the following reasons:
1. It acts as a defensive system and prevents the harmful affects of pathogens.
2. It also ensures that the different physical and biological functions of the body are effectively carried out.

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Atmosphere maintains the temperature of our planet in a steady situation, neither too much high nor too much low. This happens because of a gaseous layer present in our atmosphere which prevents the extra heating by sunlight and also too much cooling at night by absorbing the heat. The atmosphere also has a preventive layer of ozone which does not allow harmful radiations like UV rays to enter our environment. So, in this way atmosphere acts as a blanket for our planet.