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i) They are eco-friendly.
ii) They do not cause pollution like artificial fertilizers.
iii) Help to safeguard natural resourses.

(i) Ionic substances crystallize out from their saturated aqueous solution with a definite number of molecules of water.
(ii) The number of water molecules found in the crystalline substance is called water of crystallization.
(iii) Such salts are called hydrated salts.
(iv) E.g. Blue vitriol - CuSO₄.5H₂O

(i) Electric heater.
(ii) Electric iron work on the heating effect of current.

Dolphins, dogs, bats can hear the ultrasonic vibrations.

(i) "According to Newton's second law, the force acting on a body is directly proportional to the rate of change of linear momentum of the body and the change in momentum takes place in the direction of the force".
(ii) Force = mass x acceleration
(iii) F = m x a

(i) Overcome the rapid depletion of ground water levels.
(ii) To meet the increase demand of water.
(iii) Reduce flood and soil erosion.
(iv) Used for drinking purpose.

(i) To increase the productivity of crops
(ii) Remains fresh beyond their normal life time

According to Ohm's law, at a constant temperature, the steady current 'I' flowing through a conductor is directly proportional to the potential difference 'V' between the two ends of the conductor.
\(I\alpha V \Rightarrow\)  V = IR

Given: The ratio of masses of two planets \(M_{1}: M_{2} \) is 2: 3 The ratio of their radii \(R_{1}: R_{2}\) is 4: 7
\(g_{1}: g_{2}= ? \)
\(\mathrm{g}=\frac{\mathrm{G \times M}}{\mathrm{R}^{2}} ; \quad \mathrm{g}_{1}=\frac{\mathrm{G\times M}_{1}}{\mathrm{R}_{1}^{2}} ; \quad \mathrm{g}_{2}=\frac{\mathrm{G \times M}_{2}}{\mathrm{R}_{2}^{2}} \)
\(\frac{g_{1}}{g_{2}}=\frac{\frac{G \times M_{1}}{R_{1}^{2}}}{\frac{G \times M_{2}}{R_{2}^{2}}} ; \quad \frac{g_{1}}{g_{2}}=\frac{M_{1}}{R_{1}^{2}} \times \frac{R_{2}^{2}}{M_{2}}=\frac{2 \times 7 \times 7}{4 \times 4 \times 3}=\frac{49}{24}\)
∴ \(g_{1}: g_{2}\) = 49: 24

(i) Transport of respiratory gases (Oxygen and CO₂).
(ii) Transport of digested food materials to the different body cells.
(iii) Transport of hormones.
(iv) Transport of nitrogenous excretory products like ammonia, urea, and uric acid.
(v) It is involved in protection of the body and defense against diseases.
(vi) It acts as buffer and also helps in regulation of pH and body temperature.
(vii) It maintains proper water balance in the body.

(i) In a decomposition reaction, a single compound splits into two or more simpler substances by the help of heat. It is called 'Thermolysis'.
(ii) In this type of reaction, the reactant is decomposed by applying heat.
(iii) For example, It is a class of compound to element/element decomposition. i.e. a compound (HgO) is decomposed into two elements (Hg and Oxygen).

(iv) When calcium carbonate is heated, it breaks down in to calcium oxide and carbon dioxide.
(v) It is a type of compound to compound/compound decomposition.
(vi) In thermal decomposition reaction, heat is supplied to break the bonds.
(vii) Such reactions, in which heat is absorbed, are called 'Endothermic reactions'.
\(\mathrm{CaCO}_{3(\mathrm{~s})} \stackrel{\text { heat }}{\longrightarrow} \mathrm{CaO}_{(\mathrm{s})}+\mathrm{CO}_{2}(\mathrm{~g})\)

Mass of 1 mole of nitrogen \(\left(N_{2}\right)=2 \times N=2 \times 14=28 \mathrm{~g}\)
Mass of 3 moles of hydrogen \(\left(\mathrm{H}_{2}\right)=3[2 \times \mathrm{H}]\)
=3[2 x 1]=3[2]
=6 g
Mass of 2 moles of ammonia \(\left(\mathrm{NH}_{3}\right)=2\left[\mathrm{NH}_{3}\right]\)
=2[1 x N + 3 x H] 
=2[1 x14 + 3 x 1] 
=2[14 + 3] 
=2[17] = 34 g
\(\left.\begin{array}{c}1 \text { mole of nitrogen }(28 \mathrm{~g}) \\ + \\ 3 \text { mole of hydrogen }(6 \mathrm{~g})\end{array}\right\}=\text {2 moles of ammonia} (34 \mathrm{~g})\)

Application of Newton's law of gravitation
(i) Dimensions of the heavenly objects can be measured using gravitation law. Mass of the earth, radius of the earth, acceleration due to gravity etc. can be calculated with a higher accuracy.
(ii) Helps in discovering new stars and planets. Mass of the double stars can be calculated.
(iii) One of the irregularities in the motion of stars is called "Wobble" which leads to the disturbance in the motion of planet nearby. In this condition mass of the star can be calculated using law of gravitation.
(iv) Helps to explain germination of roots due to the property of geotropism, which is the property of root responding to the gravity.
(v) Helps to predict the path of the astronomical bodies.