Lakhmir Singh Manjit Kaur Biology 2020 2021 for Class 10 Science Chapter 9 - Model Test Paper 2

Answer:

As the population increases, so does their demand for energy. More and more of fossil fuels are being used to generate electricity and for transportation purposes. Use of fossil fuels in large amounts, add heat and pollution to the environment thus affecting the climatic conditions and the environment adversely.

Answer:

Balanced chemical equation:
$2{\mathrm{FeSO}}_4\stackrel{\mathrm{Heat}}{\to }{\mathrm{Fe}}_2{\mathrm{O}}_3+{\mathrm{SO}}_2+{\mathrm{SO}}_3$

Answer:

(a) When the object is at 2F₁



Nature of the image formed: Real and inverted
Position of the image formed: At 2F₂
Size of the image formed: Same as that of the object

(b) When the object is placed between the focus F₁ and optical center O.




Nature of the image formed: Virtual and erect
Position of the image formed: Same side of the object, beyond the 2F₁
Size of the image formed: Enlarged

Answer:

A decomposition reaction is a chemical reaction in which a single compound breaks down to simpler products.
Example: Decomposition of ferrous sulphate crystals.
$2{\mathrm{FeSO}}_4.7{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)\stackrel{\mathrm{heat}}{\to }{\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+{\mathrm{SO}}_2\left(\mathrm{g}\right)+{\mathrm{SO}}_3\left(\mathrm{g}\right)+7{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$
Heat the ferrous sulphate crystals, the colour of ferrous sulphate crystals is green. On heating, the ferrous sulphate crystals lose their water molecules. Therefore, the colour of the crystals change.

Answer:

 (a) Blood vessels help in transporting oxygenated and deoxygenated blood to different parts of the body.

(b) Platelets help in the process of blood clotting.

(c) Lymph carries digested and absorbed fats from the intestine. It also provides immunity to the body.

(d) Heart acts as a pump and helps circulate blood throughout the body.

Answer:

Sodium and potassium are two metals that react violently with cold water.

Observations made when such a metal is dropped in water:
(i) The reaction is highly exothermic, i.e. a huge amount of heat is produced.
(ii) Hydrogen gas is evolved in the reaction
(iii) Little explosions take place because the heat produced in the chemical reaction burns the hydrogen gas.

Hydrogen gas can be identified by the pop sound produced during the reaction of metal with cold water.

Answer:

(a) As covalent bonds do not break easily (dissociate), so they do not form ions which help in conduction of electricity. Therefore, covalent compounds don't conduct electricity as they don't have free electrons or ions.

(b) The given compound contains 3 carbons and a ketone functional group so it would be called as 'propanone'.

(c) When ethanoic acid reacts with sodium carbonate, sodium ethanoate, carbon dioxide, and water are formed.

$2{\mathrm{CH}}_3\mathrm{COOH}+{\mathrm{Na}}_2{\mathrm{CO}}_3\to {\mathrm{CH}}_3\mathrm{COONa}+{\mathrm{CO}}_2+{\mathrm{H}}_2\mathrm{O}$

To test the presence of formed gas, we pass this gas from lime water. Upon reaction, lime water turns milky, which confirms the presence of carbon dioxide in the reaction.
 

Answer:

(a) Washing soda: Chemical formula of washing soda is ${{\mathrm{Na}}_2\mathrm{CO}}_3.10{\mathrm{H}}_2\mathrm{O}$.  Washing soda used as a cleansing agent in domestic household purposes.

Baking Soda: Chemical formula of baking soda is NaHCO₃.  Baking soda is used as an antacid to remove acidity in the stomach.

(b) The chemical formula of bleaching powder is CaOCl₂.
Bleaching powder is prepared by passing chlorine gas over dry calcium hydroxide.
$\mathrm{Ca}(\mathrm{OH}{)}_2+{\mathrm{Cl}}_2\to \underset{\mathrm{bleaching} \mathrm{powder}}{{\mathrm{CaOCl}}_2}+{\mathrm{H}}_2\mathrm{O}$

Bleaching powder is used in paper factories for bleaching wood pulp, as bleaching powder is a strong oxidizing agent.

Answer:

(a) Electrolysis of acidified water:
$$\begin{gathered} \mathrm{At} \mathrm{cathode}: 2{\mathrm{H}}^{+}+2{\mathrm{e}}^{-}\to {\mathrm{H}}_2 \\ \mathrm{At} \mathrm{anode}: {\mathrm{OH}}^{-}\to \mathrm{OH}+{\mathrm{e}}^{-} \\ 4\mathrm{OH}\to 2{\mathrm{H}}_2\mathrm{O}+{\mathrm{O}}_2 \end{gathered}$$
Hence, the gas produced at cathode is hydrogen and the gas produced at anode is oxygen.

(b) A water molecule contains two atoms of hydrogen and one atom of oxygen. Therefore, during the electrolysis of water, the ratio of the amount of hydrogen gas and oxygen gas produced is 2:1. Hence, we can say that the volume of gas collected at one electrode is double than that at the other electrode

(c) As electrolysis of water is a slow process, to increase the rate of electrolysis we add dilute sulphuric acid. 
Dilute sulphuric acid increases the rate of breakdown of ions.

 

Answer:

(a)



(b) Using, $I =\frac{ P}{V}$

Current drawn by 60 W lamp is, $I =\frac{ 220}{60} = 3.67 \mathrm{A}$

Current drawn by 40 W lamp is, $I = \frac{220}{40} = 5.5 \mathrm{A}$

So, the net current drawn by the combination is = 3.67 A + 5.5 A = 9.17 A

(c) Net power of the combination = 60 W + 40 W = 100 W

So, the energy consumed in 1 h = $E=P\times t$ = 100 × 1 × 60 × 60 J = 360000 J

Answer:

(a) A series arrangement not used for connecting domestic electrical appliances in a circuit because if any one of the components connected in series stops working or get damaged, then the whole circuit would break up and no current will flow further in the circuit and none of the other devices would work. 

(b)



Two properties of magnetic field lines: 

(i) They originate from the north pole of the magnet and end at the south pole of the magnet.
(ii) They do not intersect each other. 
 

Answer:

An electric generator converts mechanical energy into electrical energy.



MNST → Rectangular coil

A and B → Brushes

C and D → Two slip rings

X → Axle, G → Galvanometer

The principle of working of an electric generator is that when a loop is moved in a magnetic field, an electric current is induced in the coil. It generates electricity by rotating a coil in a magnetic field. The above figure shows a simple AC generator.

Answer:

Answer:

Ultraviolet radiations split the oxygen molecules present in stratosphere into free oxygen atoms. These free oxygen atoms then combine with molecular oxygen to form ozone.

O₂ → O + O

O₂ + O → O₃

Ozone layer is a protective layer which protects the earth from harmful UV radiations. Any damage to the ozone layer would result in UV rays entering the earth's atmosphere. These UV rays can cause diseases such as skin cancer and cataract.
They can also adversely affect the crops.

The ozone layer is damaged as a result of chlorofluorocarbons. These are often used in refrigerators, air conditioners and fire extinguishers.

Answer:

Answer:

(a) The splitting of white light into seven colors on passing through a transparent glass prism is called dispersion of white light.

A rainbow is formed in the sky because of the dispersion of sunlight by millions of water droplets in the atmosphere. Every single water droplet behaves like a tiny glass prism that splits the white light into different colors. Different colors bend at different angles on passing through the water droplets, thus separating the white light into a natural spectrum of seven colors, as Violet, Indigo, Blue, Green, Yellow, Orange, and Red. The diagram below shows the formation of a rainbow:



(b) Hypermetropia or long-sightedness is a common eye defect, in which a person is not able to nearby objects whereas the farther objects appear clear to the person. 

(i) Hypermetropic eye:



(ii)  Correction made with a convex lens for the hypermetropic eye:

Answer:

(a) (i) The sky appears blue when viewed from Earth, because of the scattering of the light. When sunlight strikes molecules in our atmosphere, the light is redirected in many directions. The blue light is scattered more than the red light because blue color has the smallest wavelength i.e. comparable to the size of the particles present in our atmosphere. So, it is scattered the most, causing the sky to be blue.

(ii) The Sun is visible to us two minutes before the sunrise and two minutes after the sunset because of the bending of the light due to atmospheric refraction. The light from the Sun gets refracted by the atmospheric layers and reaches the observer. This causes the observer to think that the light is coming straight from the Sun.

(iii) If an object is placed very close to the eyes, the light reflected from it does not fall on the retina to form a clear image. The minimum distance for seeing an object clearly is 25 cm for the human eye.

(b) Presbyopia is a common defect of vision, which generally occurs at old age. A person suffering from this type of defect of vision cannot see the nearby objects clearly and distinctively. A presbyopic eye has its near point greater than 25 cm and it gradually increases as the eye becomes older.

Presbyopia is caused by the:

1. The weakening of the ciliary muscles.

2. Reduction in the flexibility of the eye lens.

Answer:

(a) The need to classify elements into families with similar properties arose because, lacking this basic tool, the chemist had to deal with each of the 45 or so known elements one at a time, as if there were no rhyme or reason to them.

(b) Two criteria used by Mendeleev in creating his periodic table:
(i)Mendeleev's periodic table was based on the observation that the properties of elements are the function of their atomic masses. This means that if elements are arranged in the increasing order of their atomic masses, then their properties get repeated after regular intervals.
(ii) Relative atomic mass and similarity of chemical properties.

(c) As at the time of Mendeleev some elements are not discovered, so he realized this fact and left gaps in his table for such elements and also predicted their properties.

(d) Because at the time of Mendleeve these elements are not discovered, so he did not mention about them.

(e) In the modern periodic table, all isotopes are placed in the same position as in modern periodic table is based on the atomic number not on atomic masses.

Answer:

(a) Electronic configuration of Na₂O.

Formation of ionic bond:


(b) Ionic compounds are usually hard because of inter-atomic attractive forces between them. Positively charged ion and negatively charged ion are strongly attracted towards each other and their lattice enthalpy increases.

(c) Electricity can be conducted only in the presence of free electrons/ions. In the solid state, there will be no free electrons but in the molten state, ions are free to conduct electricity.

(d) In carbon tetrachloride, four single bonds are formed. Hence, covalent bonding is present in CCl₄.

(e) In magnesium chloride, magnesium will lose its electrons and chlorine will accept those electrons to form magnesium chloride. Hence. ionic bonding is present in magnesium chloride.

 

Answer:

(a)

(b)

(i) Dendrites acquire stimulus or information from the other cells.

(ii) Axon carries away information from the cell body to the dendrite of the next neuron.

Answer:

(a) (i) The bending of shoots or other plant parts in response to light is known as phototropism.

(ii) The bending or growth of roots towards gravity is known as geotropism.

Activity -
Fill a conical flask with water and then cover the neck of the flask with a wire mesh. Place few germinating seeds on the wire mesh. Then, take a cardboard box that is open from one side. Place the flask in the box and keep this setup near a window. After 3-4 days, you will notice the shoots start bending towards light, while the roots bend away from light.

(b) (i) Auxin helps cells grow longer.

(ii) Abscisic acid inhibits growth and causes wilting of leaves.

Answer:

(a) When hydrochloric acid is treated with an active metal then hydrogen gas is released.
$2\mathrm{M}+2\mathrm{HCl}\to 2\mathrm{MCl}+{\mathrm{H}}_2$
When this hydrogen gas comes in contact with burning match stick then the gas burns with a pop sound.

(b) Sodium and potassium are two active metals which can be used with hydrochloric acid to liberate the hydrogen gas.
 

Answer:

(a) Test tube "B" has less lather due to the presence of calcium ions. Due to the presence of calcium ions water become hard and in hard water, lather formation decreases.

(b) Test tube "A" has more lather because it is soft water. In soft water, lather formation increases and cleansing action increases.
 

Answer:

(a) The ray will get reflected from the mirror and will go parallel to the principal axis of the mirror. 
 


(b) The mirror shown in the given figure is a converging mirror or a concave mirror.

Answer:

The given ammeter has 10 division between 0 and 0.5 A. 

Value of one division on the ammeter scale = 0.05 A

If the pointer shows 22 division for the main scale reading, then the actual reading = $22\times 0.05 \mathrm{A} = 1.1 \mathrm{A}$

Hence, the value of the current according to the given pointer is 1.1 A.
 

Answer:

In test tube A, anaerobic respiration will occur. The top of test tube A is covered with a film of oil which means no oxygen would be available to the yeast cells for respiration. In this case, the product of respiration will be ethanol, carbon dioxide and energy.

$\mathrm{Glucose}\to \mathrm{Pyruvate} \to 2{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH} +2{\mathrm{CO}}_2 + 2\mathrm{ATP}$

In test tube B, aerobic respiration will occur. The products of aerobic respiration will be carbon dioxide, water and energy.

$\mathrm{Glucose}\to \mathrm{Pyruvate}\to 6{\mathrm{CO}}_2 +6{\mathrm{H}}_2\mathrm{O} + 38\mathrm{ATP}$
 

Answer:

(a) The leaf should be boiled in alcohol (ethanol).
(b) The leaf is boiled in alcohol to destarch it (remove the chlorophyll from the leaf) as the chlorophyll interferes with the testing of starch with iodine.