(i) Substance X-Calcium Hydroxide.
Ca(OH)₂(aq) + CO₂(g)\(\longrightarrow \) CaCO₃(s) + H₂Cl
                                             (White ppt.)
(ii) Calcium hydroxide is obtained by reaction of calcium oxide and water.
CaO(s) + H₂O(l) \(\longrightarrow \)Ca(OH)₂(aq) + Heat

(a) (i) The reactants are copper oxide and hydrogen. Copper oxide undergoes reaction and hydrogen (H₂) undergoe oxidation.
(ii) The reactants are copper oxide and zinc. Zinc undergoes oxidation and copper oxide undergoes reduction.
(b) Calcium carbonate is reduced in industries to get CaO and CO₂.

Three properties of sodium are:
(i) Sodium is so soft that it can be cut with a knife.
(ii) It has low density.
(iii) It has low melting point.

The major differences between an electric motor and generator are stated below:
Electric Motor:
1. It converts electrical energy into mechanical energy.
2. It needs electrical energy for its works.
3. They are used as water pumps, marble grinders etc.
Generator:
1. It converts mechanical energy into electrical energy
2. It needs mechanical energy for its working.
3. They are used as water pumps, marble grinders etc.
4. diesel generator, hydro-electric generator are the examples of it.

The transport of soluble products of photosynthesis is known as translocation. Translocation in plants occurs by means of the vascular tissue known as phloem. Translocation is necessary because without it, the food prepared by the leaves cannot reach other parts of the plant.
(i)In plants, the synthesis of sugars takes place in the leaves by the process of photosynthesis.
(ii)Hormones are synthesised away from their targrt site.

(i) Oxygen enters the human body through the nasal passage and reaches the lungs.
(ii) Numerous alveoli are present in the lungs. These alveoli are surrounded by many blood capillaries. From the alveoli, 0₂ is taken up by the red blood cells present in the blood capillaries.
(iii) Similarly, the CO₂ from the various tissues is transported to the alveoli.
(iv) This CO₂ is then released through the nasal passage during exhalation. Alveoli are the sites of exchange of gases. Each lung contains 300- 350 million alveoli.
These alveoli increase the surface area for gaseous exchange, making the process of respiration more efficient.

(i) Metals are regarded as electropositive elements because they lose electrons to form metal cations.
(ii) When a piece of copper metal is added to .a solution of zinc sulphate, no change takes place since copper is less reactive than zinc and hence will not displace it from zinc sulphate solution. When some zinc is put into blue copper sulphate solution, the blue colour of the copper sulphate solution fades gradually due to the formation of colourless zinc sulphate and red-brown copper metal is deposited on the zinc strip. The reaction takes place as zinc is more reactive than copper.
\(\underset { Copersulphate\\ \quad (Blue) }{ { CuSO }_{ 4 }(aq) } +\underset { Zinc }{ Zn } \rightarrow \underset { ZincSulphate\\ (Colourless) }{ { ZnSO }_{ 4 }(aq) } +\underset { Copper\\ (Red-brown) }{ Cu(s) } \)
(iii) Articles made of aluminium do not corrode even though aluminium is an active metal as a protective layer of aluminium oxide is formed over the aluminium metal.

(a) The solar cells are costly and hence the energy available from them expensive.
(b) 15 km/h is the minimum wind velocity required to obtain useful energy with a windmill.
(c) Nuclear fission is the process in which a radioactive atom splits up into smaller nuclei when struck with low energy neutrons.

(a) The solar cooker box is covered with a plane glass plate so as to prevent heat from escaping.
(b) Sun is said to be the ultimate and the original source for most of the energy present on the earth. When sun rays fall on oceans and other water bodies, the water present in the water bodies gets evaporated and rises up in the atmosphere. In the upper part of the atmosphere, this water vapour gets condensed and forms douds, which give rain on the high lands. Therefore, the rain water runs over the Sand surface towards the large water bodies. This running water over the land surfaces is called river. Therefore, the energy of running water actually originates from the solar energy. This is why solar energy of water flowing in a river is considered to be an indirect form of solar energy.
(c) The fission of nucleus is brought about by splitting the nucleus of heavy atoms, such as uranium or plutonium, with low-energy neutron bombardment. 

Chemical coordination is performed by hormones, which are chemical messengers secreted by endocrine glands.
These hormones coordinate the activities of living organisms and also their growth.
The timing and the amount of hormones released are regulated by the feedback mechanism.

(a) Short circuiting is the term used for defining the situation in which the neutral and live wires of an electric circuit come in direct contact. When too many electrical appliances are connected to a single socket, the appliances drawn much more current or power that the permissible limit from the main supply. This situation is termed as overloading.
(b) Resistivity of an alloy is much higher than its constituent metals Moreover, alloys do not oxidise as easily as the constituent metals at high temperature. Because of these reasons, coils of electric testers are made of an alloy rather than a pure meta.

The function of receptors in our body is very important as they collect informations about changes in the environment around us. Receptors then pass the same information in the form of nerve impulse to the central nervous system, where the information is processed and the ultimate response is given. Now, for example, if the gustatory receptors of our tongue do not work properly, we will not be able to know the taste of different types of foods (whether it is sweet, salty, sour or bitter, etc.)

(a) Following is the relation between hydrogen ion concentration of an aqueous solution and its pH.

(b) If the pH of the solution decreases from 3 to 2, then

           \({pH_1\over pH_2}={-log[H^+]\over -log[H^+]_2}\)

\(\therefore {-log[H^+]_1\over -log [H^+]_2}={3\over 2}\)

\(\therefore {[H^+]_1\over [H^+]_2}={10^{-3}\over 10^{-2}}\)

or, \([H^+]_2=10[H^+]_1\)

Hence, hydrogen ion concentration will increase 10 times.

Silver coin with atmospheric sulphur and green coating is of copper carbonate which is formed due to the reaction of copper with moist carbon dioxide from the air.

Balanced Equation
\(2{ FeSO }_{ 4 }\overset { Heat }{ \rightarrow } { Fe }_{ 2 }{ O }_{ 3 }(s)+S{ O }_{ 2 }(g)+{ SO }_{ 3 }(g)\)

Non-metal (lustrous) = Iodine (I)
Metal (non-lustrous) = Sodium (Na)

Gallium.

Since element A is placed in group 14, therefore, its valence is 14 - 10 = 4 . Further, since it is difficult to either lose all the four valence or gain four more electrons, therefore, it prefers to share these four electrons to acquire the stable electronic configuration of the nearest inert gas. Thus the nature of the chloride of element A is covalent.

(i) Catenation  
(ii) Tetravalency of carbon

-CH₂ - is the difference in the molecular formula of any two consecutive members of a homologous series of organic compounds.

A compass needle is a small bar magnet.

Oxidation-reduction reaction

Direction of induced current is given by Fleming's right hand rule according to this rule, stretch the thumb, fore-finger and the middle finger of the right hand such that they are mutually perpendicular.
If the fore-finger points in the direction of magnetic field the thumb shows the direction of motion and middle finger points in the direction of induced current.

The processes that together perform the maintenance functions of living organisms are called life processes.

It behaves like a magnet.

Elements which lose electrons to form positive ions are called metals.

CO₂ is obtained from leaves through stomata pores and N₂ is obtained in combined form, e.g. nitrates, through roots in dissolved form.

We know that for making an electromagnet we need to place a soft iron core inside a solenoid. Soft iron is a ferro-magnetic material and hence it augments the magnetic property of solenoid by thousands of times. Thus, for making a permanent electromagnet, we need to place a soft iron core inside a solenoid.

If platelets are not present in the blood, then clotting at the site of injury will not take place. This will result in continuous bleeding and could be fatal for the organism.

X - Carbon; Y - Diamond and Z - Graphite

The functional junction between two neurons is called synapse.

Hind brain

Nerves which originated from the brain are called cranial nerves.

Earth wire is used to provide a low resistance conducting path to any charge that gets leaked into the body of the appliance.

A measuring instrument used to measure potential difference between two points in an electric circuit.

It means that 1 joule of work will be done in order to move 1 coulomb of charge from point A to B.

(i) Scale for measuring [H⁺] concentration in a solution is called pH scale.
(ii) pH of Neutral solution is 7
pH of Acidic solution is 0 to below 7
pH of Basic solution is 7 to 14

(a) The eating up of metals by the action of air and moisture on their surface is called corrosion.
      (i) Metal which does not corrode on being kept in the atmosphere is gold.
     (ii) Metal which corrodes on being kept in the atmosphere is iron.
(b) Take three boiling tubes and label them as A, B, and C. Place clean iron nails, free from rust, in each tube. Add water to tube A in such a manner that some parts of the nails are exposed to air and seal it with the help of a rubber cork. Add boiled water to tube B in such a way that the nails are completely submerged. Then, pour some amount of kerosene oil in the tube and seal it with the help of a rubber cork. Add anhydrous calcium chloride to tube C and then seal it. Leave the tubes undisturbed for two weeks and observe the changes. 

The salivary glands secrete saliva. The saliva contains water, salts, mucus and an enzyme ptyalin. The enzyme ptyalin, also glycogen and convert them into maltose. The mucus and water makes the food soft and slippery for the formation of bolus and also protects soft lining of alimentary canal. Thus the digestion of starch i.e., carbohydrate begins in the mouth. Since,the food remains in the mouth only for a short time and so, the digestion of food remains incomplete.
\(Starch(Carbohydrates)+Glycogen\overset { Ptyalin }{ \longrightarrow } Maltose\)
The partially digested food is further digested in the stomach. The food is broken down into smaller pieces and churned to form a semi-solid paste. The wall of the stomach contains three tubular glands. These glands secrete gastric juice. The gastric juice contains hydrochloric acid, mucus, pepsin, gastric lipase and rennin.
Hydrochloric acid:
It softens the food
It makes food acidic for the function of pepsin
It stops the action of salivary amylase
It kills germs and bacteria to disinfect the food
It converts inactive pepsinogen and prorennin into active pepsin and rennin.
\(InactivePepsinogen\overset { HCI }{ \longrightarrow } ActivePepsin\\ InactivePro-rennin\overset { HCI }{ \longrightarrow } Activerenin\)
Pepsin: It hydrolyses proteins into soluble proteoses and peptones only in presence of hydrochloric acid.
\(Protein\overset { Pepsin }{ \longrightarrow } Peptones+Proteoses\)
Rennin: It is active only in infants. The main function of rennin is that it converts soluble milk protein casein into insoluble protein called paracasein. Due to this, milk stays in stomach for longer duration.
\(\underset { (solublemilkprotein) }{ Casein } \overset { Rennin }{ \longrightarrow } \underset { (Insoluble) }{ Paracasein } \)
Mucus: The main function of mucus is to protect the inner lining of stomach from corroding action of hydrochloric acid as well as from pepsin enzyme.
Small Intestine: It is the seat of major digestion and absorption. Small intestine receives the secretion of two glands namely,
(i) Liver, (ii) Pancreas
Liver: It is the largest gland of the body. It is reddish brown in colour. It has soft pear - shaped sac called gall bladder. The gall bladder secretes bile juice. Bile is alkaline containing bile pigment. Thus, bile is stored in the gall bladder. It helps to emulsify or break the fats or lipids present in the food.
The bile performs the following functions:
(i) It breaks the larger globules of fat into small globules to make the enzyme to act and digest them.
(ii) It prevents putrefaction of food.
(iii) The bile creates a medium for the pancreatic juice to act on food by neutralizing the acidity in the food.
Pancreas: Pancreas secretes a digestive fluid called pancreatic juice. This juice contains digestive enzymes such as trypsin, nucleases, pancreatic lipase and pancreatic amylase. The enzyme trypsin digests the proteins, the enzyme pancreatic amylase breaks down the starch and the enzyme lipase breaks down the emulsified
facts. Pancreas produces two important hormones namely,
(i) Insulin, (ii) Glucagon
Insulin is essential for using glucose and storing it into glycogen. Glucagon is essential for conversion of glycogen into glucose. The alkaline medium is favourable
for the action of pancreatic enzymes.
\(Starch\xrightarrow [ ]{ Pancreaticamylase } Maltose\\ Fat\xrightarrow [ ]{ Lipase } Fattyacids+Glycerol\\ Proteins\xrightarrow [ ]{ Trypsin } Peptides\)
Secretion of intestinal juice by liver and pancreatic glands
The intestinal juice contains a number of enzymes which complete the digestion process. Here, the complex carbohydrates are converted into glucose, proteins are converted into amino acids and fats are converted into fatty acids and glycerol. All these end products i.e., amino acids, glucose, fatty acids and glycerol are small
and water soluble molecules. This complete digestion of food takes place by biological catalysts called enzymes. The intestinal juice includes - maltase, invertase, lactase etc.
\(Peptides\xrightarrow [ ]{ Trypsin } Aminoacids\\ Sucrose\xrightarrow [ ]{ Invertase } Glucose+Fructose\\ Maltose\xrightarrow [ ]{ Maltose } Glucose+Glucose\\ Lactose\xrightarrow [ ]{ lactose } Glucose+Galactose\)