Lakhmir Singh & Manjit Kaur 2019 Solutions for Class 10 Science Chapter 11 - Model Test Paper 4

Answer:

Aluminium powder is used as the reducing agent to obtain manganese from its oxide.

$2\mathrm{Al}\left(\mathrm{s}\right)+3\mathrm{MgO}\to {\mathrm{Al}}_2{\mathrm{O}}_3+3\mathrm{Mg}\left(\mathrm{s}\right)$

Answer:

When a light ray travels from one medium to another, then due to change in the density of the medium, speed of light changes. Change in the speed of the light at the boundary of two media force the light ray to bend from its original path.

Answer:

When gypsum is heated at 373 K, it gives plaster of paris,

${\mathrm{CaSO}}_4.2{\mathrm{H}}_2\mathrm{O}\to \underset{\mathrm{plaster} \mathrm{of} \mathrm{paris}}{{\mathrm{CaSO}}_4.\frac{1}{2}{\mathrm{H}}_2\mathrm{O}}+1\frac{1}{2}{\mathrm{H}}_2\mathrm{O}$

Plaster of paris becomes hard when the appropriate amount of water is available.

$\underset{\mathrm{plaster} \mathrm{of} \mathrm{paris}}{{\mathrm{CaSO}}_4.\frac{1}{2}{\mathrm{H}}_2\mathrm{O}}+1\frac{1}{2}{\mathrm{H}}_2\mathrm{O}\to {\mathrm{CaSO}}_4.2{\mathrm{H}}_2\mathrm{O}$

In hospitals, it is used as a plaster to support broken or fractured bones.

 

Answer:

Only two rays are required for the image to be located.

Image diagram to show the formation of a virtual image formed by a concave mirror:

Answer:

(a) ethanol, carbon dioxide and energy - Anaerobic respiration
(b) carbon dioxide, water and energy - Aerobic respiration
 

Answer:

Functional group that can be hydrogenated is alkene.
Hydrogenation of oils(unsaturated alkene):

Vegetable oil is unsaturated fatty acids having a double bond in between some of their carbon atoms. When vegetable oil is heated in the presence of nickel catalyst, then a saturated fatty acid called vegetable ghee is formed. This reaction is known as a hydogenation reaction.
When vegetable oil is hydrogenated, it changes from liquid state to solid state.

Vegetable ghee is generally produced by hydrogenation of vegetable oil or animal oil.

Answer:

(a) Solid A is assumed to be aluminium (Al) and solid B to be manganese oxide. When the mixture of manganese oxide and aluminium is heated, manganese is produced in the molten state and aluminium oxide floats over it. Manganese produced in the molten state as a lot of heat energy is released in the process. Therefore, C is manganese and D is aluminium oxide.
$\mathrm{Al}\left(\mathrm{s}\right)+{\mathrm{MnO}}_2\left(\mathrm{s}\right)\to \mathrm{Mn}\left(\mathrm{s}\right)+{\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)$

(b) The type of reaction under which the above reaction is classified are:
1. Redox reaction
2. Displacement reaction

Answer:

(a) A and G form an ionic compound so A must be a metal of group 1 and G must be a non-metal of group 17. As the ionic compound of A and G is obtained from seawater so that ionic compound must be sodium chloride. Therefore, A and G belong to the third period of the periodic table.

(b) Because all the given elements belong to the third period and H being the last element of the third period will be the noble gas.

(c) A belongs to the first group of the periodic table, so it has the largest radius. 

(d) Oxides of E and F are acidic in nature, so they are non-metals.

(e) The oxide of D is almost neutral, so it is a metalloid.

Answer:

(a) MgSO₄ (aq) + Cu(s) → CuSO₄ (aq) + Mg(s)
Copper is less reactive than magnesium, so copper cannot displace magnesium. Hence, this reaction will not occur.

(b) CuSO₄ (aq) + Fe (s) → FeSO₄ (aq) + Cu(s)
Iron is more reactive than copper, so it will displace copper from copper sulphate and form iron sulphate.

(c) MgSO₄ (aq) + Fe (s) â€‹→ FeSO₄ (aq) + Mg(s)
Iron is less reactive than magensium, so iron can not displace magnesium. Hence, this reaction will not occur.

Answer:

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. 

Hypermetropia deffect: 

​


Correction made with a convex lens for the hypermetropic eye:




A convex lens is used to correct the defect of hypermetropia. 

Answer:

The focal length of the convex lens, f = +18 cm

Image distance, v = + 36 cm

Using lens formula, $\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$

$$\begin{gathered} \Rightarrow \frac{1}{36}-\frac{1}{u}=\frac{1}{18} \\ \Rightarrow \frac{1}{u}=\frac{1}{36}-\frac{1}{18}=-\frac{1}{36} \\ \Rightarrow u =- 36 \mathrm{cm} \end{gathered}$$

Magnification of the lens = $m = \frac{v}{u}=\frac{36 \mathrm{cm}}{-36 \mathrm{cm}}= -1$

Answer:

The direction of the flow of current can be found out by Maxwell's Right Hand Thumb Rule. It states that if we point our right-hand thumb in the direction of current then the fingers of our hand curl along the direction magnetic field. 

Now it is given that the magnetic field is in the anti-clockwise direction. If we look at the conductor from the right and apply the Thumb rule, the direction of current would be towards the East. However, if you look at the field from the left and apply this rule, the direction of current would be towards the west.

Answer:

Analogous organs: These are organs that have different origins, but perform similar functions.

Homologous organs: These are organs that are similar in origin (or are embryologically similar), but perform different functions.

The wings of an insect and wings of a bat are examples of analogous organs.

The forelimbs of frog and forelimbs of humans are examples of homologous organs.

Answer:

(a) (i) Implantation is the process wherein a fertilised egg (zygote) formed in the fallopian tube gets embedded on the walls of the uterus, inside the female body.

(ii) Placenta is a vascular structure present in the inner lining of the uterus. It is connected to the foetus by the umbilical cord. The embryo receives nutrition and oxygen from the mother’s blood via the placenta.

(b) The average duration of human pregnancy is nine months.

Answer:

The automatic action or response provoked by a stimulus is known as reflex action. The sensory nerves that detect the stimulus are connected to nerves that move the muscles. Such a connection is called reflex arc. The reflex arc connections meet in a bundle in the spinal cord. The signal and the response that has taken place reach the brain but the brain does not coordinate the reflex response.

For example, we withdraw our hands on touching any hot article.

Answer:

(a) When Mendeleev developed the periodic table, he realized that many elements are missing in the periodic table and yet to be discovered. So, left gaps in his table for such elements and also predicted their properties.

(b) Limitations of Mendeleev's classification:
1. He could not explain the position of isotopes in the periodic table.
2. He could not assign a proper position to the element hydrogen in the periodic table.
3. He failed to explain the wrong order of atomic masses of some elements.

(c) As we move from left to right in a period, the atomic number will increase due to the increase of electrons in the shell.

Answer:

Refining of metals: Refining of metals is nothing but the removal of impurities from crude metals or purifying the crude metal.
Electrolytic refining is the most widely used method for the refining of metals.
Electrolysis of copper:

Electrolysis of copper from copper sulphate solution is done using copper electrodes. The crude copper serves as the anode while the thin sheet of pure copper serves as the cathode.
$$\begin{gathered} \mathrm{At} \mathrm{anode}: \mathrm{Cu}\to {\mathrm{Cu}}^{+2}+2{\mathrm{e}}^{-} \\ \mathrm{At} \mathrm{cathode}: {\mathrm{Cu}}^{+2}+2{\mathrm{e}}^{-}\to \mathrm{Cu} \end{gathered}$$
As the anode dissolves away, the cathodes on which the pure metal is deposited grow in size.
 

Answer:

The process of digestion of food in mouth, stomach and small intestine is described as follows:

1. Mouth - Digestion of food begins in the mouth. Saliva present in mouth contains a digestive enzyme, called salivary amylase, which breaks down starch into sugar.

2. Stomach - Stomach stores and mixes the food received from the oesophagus with gastric juices. The main components of gastric juice are hydrochloric acid, mucus and pepsinogen.

Hydrochloric acid dissolves bits of food and creates an acidic medium. In this medium, pepsinogen is converted to pepsin, which is a protein-digesting enzyme. Mucus protects the inner lining of the stomach from the action of HCl.

3. Small intestine - Small intestine is the site for complete digestion of carbohydrates, proteins and fats. It produces intestinal juice from the glands present in its wall. The intestinal juice helps in further digestion of food. Small intestine also obtains digestive juices from liver and pancreas that helps in mixing of food.

The liver produces bile juice that causes emulsification of fats and the pancreas produces pancreatic juice for digesting proteins and emulsified fats.

This digested food is finally absorbed through the intestinal walls.

Answer:

(a) Photosynthesis is the process by which plant cells prepare food (carbohydrates) from inorganic raw materials such as carbon dioxide and water in presence of sunlight and chlorophyll.

The factors other than sunlight affecting the rate of photosynthesis are:

• Carbon dioxide − Carbon dioxide acts as the substrate for photosynthesis. During this process, carbon dioxide and water are converted into carbohydrates.
• Water − During photosynthesis, water is photolysed into oxygen and hydrogen and it provides the energy for photosynthesis.
• Chlorophyll − Chlorophyll is the green pigment present in the leaves which absorbs sunlight.

(b) Experiment to demonstrate that light is necessary for photosynthesis:

1. Take two potted plants. Place one plant in a dark room and the other in a room receiving sufficient sunlight.
2. After 3-4 days, take one leaf each from both the plants. Bathe the two leaves first in hot water and then in alcohol.
3. Add some drops of iodine solution on the leaves.

Observation:

It can be observed that the leaf taken from the plant kept in sunlight develops blue-black patches whereas the leaf taken from the plant kept in the dark room does not show any patches.

Reason for the observation:

Plants which receive sunlight prepare their own food through the process of photosynthesis. It is the presence of starch that turns the colour of iodine solution blue-black. Therefore, blue-black patches are observed on the leaf taken from the plant kept in sunlight. In contrast, the leaf of the plant kept in the dark room does not produce any starch. Therefore, no patches are observed on it.

Answer:

(a) The magnetic field is defined as the space surrounding a magnet in which magnetic force is exerted. The direction of magnetic field lines at a place can be determined by finding the deflection in the needle of a magnetic compass. 

(b) The rule for determining the direction of the magnetic field of a current carrying wire is the right-hand thumb rule.

Right-hand thumb rule: The right-hand thumb rule indicates the direction of the magnetic field for a know direction of the current. If the thumb of the right-hand points along the direction of current then the curled fingers of that hand gives the direction of the magnetic field due to the current.


 

Answer:

Applied voltage = V

Let the current in the circuit = I

If total resistance of the circuit is R_net, then

$I=\frac{V}{R_{\mathrm{net}}}$

As all the resistances are connected in parallel, so all of the resistors will get an equal voltage across their ends.

The total current in the circuit is simply the sum of the current passing through each resistance. 

$$\begin{gathered} I =I_1+I_2+I_3 \\ \Rightarrow \frac{V}{R_{\mathrm{net}}}=\frac{V}{R_1}+\frac{V}{R_2}+\frac{V}{R_3} \\ \Rightarrow \frac{1}{R_{\mathrm{net}}}=\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_3} \end{gathered}$$


An ammeter is low impedance device which is always connected in the series with the circuit so that maximum of the current can pass through it and it can give a more accurate value of the current flowing in the circuit. 

A voltmeter is a high impedance device which is always connected in parallel in the circuit so that it does not draw any current and can give the actual voltage drop across the component.

Answer:

(a) A convex lens is shown in the diagram.

(b) It is converging in nature.

Answer:

(a) When the bar magnet is moved quickly towards the coil, a deflection is observed in the galvanometer. This deflection indicates that some current is produced in the coil. 

(b) When we move the magnet quickly away from the coil, this time the deflection is indicated in the opposite direction. It indicates the current produced in the coil is in the opposite direction.

(c) When we simply move the magnet near the face of the coil then no deflection is found in the galvanometer, because of the absence of relative motion between the coil and the magnet.

The phenomenon involved is known as Electromagnetic induction. 

Answer:

When dilute hydrochloric acid is mixed with that salt a gas is produced which extinguished a burning match-stick that means the gas produced is carbon dioxide. 
So, the salt must be sodium bicarbonate.
$\mathrm{HCl}+{\mathrm{NaHCO}}_3\to \mathrm{NaCl}+{\mathrm{H}}_2\mathrm{O}+{\mathrm{CO}}_2$

(a) Hence, the gas produced is carbon dioxide.

(b) White powdery salt is sodium bicarbonate(NaHCO₃).
 

Answer:

When Ravi places zinc plate in a blue colored solution of metal sulphate, he found that colour of the solution is fading that means zinc is more reactive than that metal and displacing it from the solution. As the solution becomes colourless after some time it shows that metal M will be copper.

(a) Zinc is more reactive than metal M.

(b) Due to the formation of zinc sulphate solution becomes colourless. 
 $\mathrm{Zn}+\underset{\mathrm{blue}}{{\mathrm{CuSO}}_4}\to \underset{\mathrm{colourless}}{{\mathrm{ZnSO}}_4}+\mathrm{Cu}$
 

Answer:

(a) The plant is kept in dark so as to destarch it, so that in the beginning of the experiment itself, the leaves do not have any starch.
(b) After the plant is destarched by keeping it in dark, it is again placed in sunlight so that photosynthesis can occur. This would result in the synthesis of starch. The leaves are again destarched by boiling them in alcohol before testing them with iodine.

Answer:

(a) (i) Tall - Plant B
(ii) Dwarf - Plant A

(b) In pea plants, tallness is a dominant trait whereas dwarfness is a recessive trait. Plants like A do not appear in the F₁ generation but reappear in the F₂ generation which means that plant A is dwarf whereas plant B is tall.



We can see from the cross that, tall plants appear in the F₁ generation but no dwarf plants are seen.
The dwarf plants are seen in F₂ generation.