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.

i) Aldehyde, (ii) Carboxylic acid.

C₄H₁₀ and C₅H₁₂

Silver or Copper.

Metal- mercury, Non-metal- bromine.

1 M HCl has a higher concentration of H⁺  ions because when HCl dissolves in water it dissociates completely into ions while CH₃COOH is a weak acid and does not dissociate into ions completely.

Nichrome should be used as a heating element in an electric iron because its melting point is higher than iron and silver.

A generator works on the basis of electromagnetic induction.

Soap is alkaline in nature. Hence, it turns red litmus paper blue and have no effect on the blue litmus paper.

Blood flow will increase upon the pressure of blood in the blood vessels. The oxygenated blood flowing through the artery doesnot have any impact as the arteries are thick walled, highly elastic blood vessels having narrow lumen and no valves.

It is a device that converts mechanical energy into electrical energy.

Magnetic field of a magnet contains magnetic field lines in it.

Aluminium.

Excretion and osmoregulation.

The transport of food from the leaves to the different parts of the plant is called translocation.

(a) All the appliances work at the same voltage as that of the electric supply.
(b) If one of the other appliances is out of order, all the other appliances keep on working as the circuit is not broken.

Spinal nerves and cranial nerves.

Thyroxine is the hormone secreted by the thyroid gland. This hormone regulates the metabolism of carbohydrates, fats and proteins. By regulating the metabolism it helps in optimum growth and development of the body.

The part of the hindbrain that takes part in the regulation of respiration is medulla oblongata.

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

Ammeter is connected in series and voltmeter is connected in parallel.

Rust is the hydrated iron (III) oxide, Fe₂O₃.xH₂O.

Hydrogen gas is evolved.

Hydrogen gas is produced when dilute hydrochloric acid is added to a reactive metal.
Fe(s)    +    H₂SO₄ (aq)      \(\rightarrow\) FeSO₄ (aq)    + H₂(g)
Iron        Dil. Sulphuric acid  Ferrous sulphate   Hydrogen 

(a) Mg(s) + Cl₂(g) \(\rightarrow\) MgCl₂
It is a combination reaction
(b) 2HgO(s) \(\overset {Heat}{\rightarrow}\) 2Hg(l) + O₂(g)
It is a thermal decomposition reaction.
(c) 2Na(s) + S(s) \(\rightarrow\) Na₂S(s)
It is a combination reaction
(d) TiCl₄(l) + 2Mg(s) \(\rightarrow\) Ti(s) + 2MgCl₂
It is a displacement reaction
(e) CaO(s) + SiO₂(s) \(\rightarrow\) CaSiO₃(s)
It is a combination reaction
(f) 2H₂O₂(l) \(\overset{uv}{\rightarrow}\) 2H₂O(l) + O₂(g)
It is a decomposition reaction

These fertilisers (CaO, Ca(OH)₂, CaCO₃] are of basic nature. Therefore, their use will be beneficial, if the soil is acidic. The purpose is to neutralise or decrease the acidity of the soil.

(i) If H⁺ ion concentration is more, pH will be less and vice versa or pH of a solution is inversely proportional to H⁺ ion concentration or pH 52 log (H⁺).
(ii) This solution is neutral.
(iii) 1MNaOH solution.
(iv) When the pH in the mouth is below 5.5, bacteria present in the mouth produce acids by degradation of sugar and corrode the tooth enamel. It can be prevented by using tooth pastes which are generally basic.
(v) As hydronium [H₃O]⁺ ion.

\(\underset{Carbon}{C}+\underset{Chlorine}{2Cl_2}\xrightarrow{Heat}\underset{Carbon\ tetrachloridse}{CCl_4}\)
Its electron dot structure and structural formulae are:

b) Saponification - Alkaline hydrolysis of an ester to give the salt of the corresponding
acid and the alcohol is called saponification. It is reverse of esterification reaction.
For example.
\(\underset{Ester}{CH_3COOC_2H_5}+\underset{sodium\ hydroxide}{NaOH}\xrightarrow{Heat}\underset{Sodium\ acetate}{CH_3COONa}+\underset{Ethanol}{CH_3CH_2OH}\)
Dehydration means removal of a molecule of water. When ethanol is heated with
conc. H2SO₄ at 443 K, it undergoes dehydration to form ethene.
\(\underset{Ethanol}{CH_3CH_2OH}\xrightarrow{Conc. H_2SO_4,443K}\underset{Ethene}{CH_2=CH_2+H_2O}\)

(a) When we magnetise a piece of magnetic material such as soft iron by keeping it inside a coil and then passing current through it, the magnet so formed is called electromagnet.
(b) (i) Steel is used to make permanent magnet.
(ii) Soft iron is used to make temporary magnets.
(c) Take a coil of wire having N number of turns and then wound it around a soft iron core. Connect the end of the wire with a battery and plug key and then let current pass through the coil. While current is passing through the coil, bring a compass near the coil. It will be observed that compass needle shows deflection. This shows that the coil will have a magnetic field of its own. The magnet so formed is called an electromagnet.

Ore A gives CO₂ and ore B gives SO₂ . Therefore, ores are MCO₃ and MS.
A can be converted into metal by the following steps :
\({ MCO }_{ 3 }\underrightarrow { Calcination } MO+{ CO }_{ 2 }\\ MO+C\underrightarrow { Reduction } M+CO\)
B can be converted into metal by the following steps :
\(2MS+{ 3O }_{ 2 }\underrightarrow { Roasting } 2MO+{ 2SO }_{ 2 }\\ \quad \quad \quad MO+C\rightarrow M+CO\)

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.
\(Peptides\xrightarrow [ ]{ Trypsin } Aminoacids\\ Sucrose\xrightarrow [ ]{ Invertase } Glucose+Fructose\\ Maltose\xrightarrow [ ]{ Maltose } Glucose+Glucose\\ Lactose\xrightarrow [ ]{ lactose } Glucose+Galactose\)

A number of resistors are said to be connected in series, if these are joined end to end and the same, current flows through each one of them when a potential difference is applied across the combination. If we connect ammeter first between the point A and R₁, then between R1 and R₂:R₂ and R₃ and lastly between R₃ and the point B; it is same as current.

(a) \(2Cu(NO_3)_2\xrightarrow{Heat}2CuO+4NO_2+O_2\)
    The brown gas so formed in this reaction is nitrogen dioxide.
(b)Thus, the brown gas 'X' is nitrogen dioxide
(c)This is a Decomposition reaction
(d)Nitrogen dioxide forms nitric acid when reacts with water. The pH value of an acid is less than 7 to 0. Thus the pH range of the aqueous solution of gas 'X' i.e.                   Nitrogen dioxide may be from 0 to less than 7.
    The reaction between nitrogen dioxide and water can be written as follows:-
    \(2NO_2 + H_2O\rightarrow HNO_2 + HNO_3\)

(a) (i) Ca(OH)₂ + CO₂\(\longrightarrow \) CaCO₃ + H₂O
(ii) Ca(OH)₂(aq) + CO₂(g)\(\longrightarrow \) CaC0₃(s) +H₂O(I)
CaCO₃(s) + H₂O(I) + CO₂(g) \(\longrightarrow \) Ca(HCO₃)₂ (aq)
(b) Aragonite and calcite

(i) Copper is more reactive than silver. Hence, when copper wire is dipped in silver nitrate solution, it displaces silver from AgNO₃ solution forming copper nitrate which is bluish green in colour.
\((ii)\quad Cu+2AgN{ O }_{ 3 }\longrightarrow \underset { Copperr\quad (II)\quad nitrate\\ bluish\quad green }{ Cu{ (N{ O }_{ 3 }) }_{ 2 } } +\underset { Silver }{ 2Ag } \)

(a) Sodium (Na) > Aluminium (A1)> Copper (Cu) > Gold (Au).
(b) 3MnO₂(s) + 4A1(s) \(\overset { \Delta }{ \longrightarrow } \) 3Mn(l) + 2A1₂O₃(s)+ Heat.

(i) Non-metals are electron accepters, they cannot supply electrons so as to convert H+ ion to H₂(g).
(ii) Like metals, hydrogen can lose an electron to form positive H⁺ ion.
(iii) Aluminium is covered with a strong protective layer of oxide which protects the metal from further corrosion.

(i) Tomato - Malic acid and citric acid
(ii) Vinegar - Acetic acid
(iii) Tamarind - Tartaric acid and citric acid.

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 different constituents of blood are plasma (the fluid part of the bloo(d) and blood corpuscles consisting of RBCs, WBCs, and platelets)
WBCs are known as the soldiers of the body because they fight against the pathogenes that invade our body, thus preventing the occurence of diseases.

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.

(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. 

(a) A solar cell is a device which converts solar energy into electricity. It is a sandwich of a silicon-boron layer and a silicon-arsenic layer.
(b) Biogas is an ideal fuel for domestic use because it is a cheap and clean fuel, which does not leave behind any residue.
(c) A nuclear power plant is a device in which controlled chain reaction is used.

(a) Ohm's Law states that at constant temperature, current flowing through a conductor is directly proportional to the       potential difference across its ends.

(a) Resistance is defined as the property of a conductor due to which it opposes the flow of current through it. The S.I. unit of resistance is Ohm \(\left( \Omega \right) \).
(b) (i) The resistance (R) of a conductor is related to its length (l) and area of cross section (A) as
          \(R=\frac { p\times l }{ A } \)  Where \(\rho \) is the resistivity of the conducting material.
Let R₁= Resistance of the original wire
      R₂= Resistance of the wire when its length is doubled
I₁= Length of original wire
l₂= Length of original wire when doubled
A₁= Area of the original wire
A₂= Area when it is halved 
Therefore,
 \({ R }_{ 1 }=\frac { P\times { l }_{ 1 } }{ { A }_{ 1 } } \quad \quad ---\quad (1)\\ { R }_{ 2 }=\frac { P\times { l }_{ 2 } }{ { A }_{ 2 } } \quad \quad ---\quad (2)\)
Dividing equation (1) and (2) by equation (1), we obtain
\(\frac { { R }_{ 1 } }{ { R }_{ 2 } } =\frac { { l }_{ 1 } }{ { l }_{ 2 } } \times \frac { { A }_{ 1 } }{ { A }_{ 2 } } \quad ---\quad (3)\)
It is given that:
\({ l }_{ 1 }=2l_{ 1 }\quad and\quad { A }_{ 2 }=\frac { 1 }{ 2 } { A }_{ 1 }\\ \)
Putting these values in equation (3), we obtain
R₂=4R₁
Hence, the resistance of the wire will be 4 times of the original value.
(ii) The resistivity will not change on stretching the wire. Resistivity is the property of the conducting material. It does not depend on the dimension of the wire. As materials of both the wires are the same, the resistivity will not change.

(1) Valency. Elements belonging to same group have same number of valence electrons and thus same valency.
Valency in a particular period from left to right first increases as positive valency and then decreases as negative valency.
Example, in elements of 2nd period:
Li has 1⁺ valency, then Be2⁺ , C4⁺ covalency, N3- valeI!cy, then 0^2- and F^(-) valency.
(2) The atomic size or atomic radius increases as we move down in a group and it decreases as we move from left to right in a period. Atomic size increases down a group due to increase in the number of shells. Atomic size decreases along a period due to increase in the nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom.
(3) Metallic and non -metallic properties. In the modern periodic table metals are on the left size and non-metals are on the right size. A zigzag line of metalloids separates metals from non-metals. Metallic character decreases from left to right in a period and increases while going down in a group. Non-metallic character increases from left to right in a period due to increase in the electron-negativity and this character decreases from topo to bottom in a group due to decrease in the electro-negativity of atoms while going down in a group.

i) All fossil are the remains of the prehistoric plants and animals. Th energy of the fossil fuels is in fact that solar energy which was trapped by natural processes a long time ago.
ii) Solar energy also appears in the form of energy of water flowing in rivers as is obvious from the water cycle in nature. It is this energy which generates in hydroelectric power plants.
iii) Biomass energy is also the solar energy absorbed by the plans which convert it into chemical energy through photosynthesis.
iv) Human and animals use bioenergy to carry out their life activities.
v) Solar energy is one of the main factors responsible for the movement of air in the atmosphere leading to wind energy.
vi) Solar energy is used directly in solar.