The atomicity of an element can be derived using Avogadro's hypothesis. Let us consider the following equation

According to Avogadro's law, 1 volume of any gas occupy 'n' number of molecules.

if n = 1 then

(i) 1 molecule of hydrogen chloride gas is made up of \(\frac{1}{2}\) molecule of hydrogen and \(\frac{1}{2}\) molecule of chlorine
(ii) But 1 molecule of hydrogen chloride contains one atom of hydrogen and I atom of chlorine
(iii) Hence \(\frac{1}{2}\) molecule of hydrogen = 1 atom of hydrogen
(iv) Or 1 molecule of hydrogen = 2 atoms of hydrogen
(v) So the atomicity of hydrogen is 2, and molecular formula is H₂
Similarly,
\(\frac{1}{2}\) molecule of chlorine = 1 atom of chlorine 1molecule of chlorine = 2 atoms of chlorine So the atomicity of chlorine is 2, and its molecular formula is Cl₂

(i) A chemical messenger is any compound that serves to transmit a message.
(ii) Hormones act as chemical messengers which are produced by specialized glands.

(i) Rh factor was discovered by Landsteiner and Wiener in 1940. It was named so because it was first discovered in Rhesus monkey.

Conditions necessary for rusting of iron:
(i) Iron is exposed to moist air.
(ii) Presence of water droplets in the atmosphere.
(iii) Presence of Oxygen.

\(\text { Molar mass of } \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}=\mathrm{Al} \times 2+3[\mathrm{~S} \times 1+\mathrm{O} \times 4]\)
\(27 \times 2+3[32 \times 1+16 \times 4]\)
= 54 + 3[32 + 64]
= 54 + 3 [96]
Molar Mass = 54 + 288 = 342
\(\text { Mass } \% \text { of an element }=\frac{\text { mass of that element in the compound }}{\text { molar mass of the compound }} \times100\)
\(\text { Mass } \% \text { oxygen in } \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}=\frac{192}{342} \times 100 \)
\(=0.5614 \times 100=56.14 \% \)
\(\text { Mass } \% \text { of oxygen in } \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3} \text { is } 56.14 \%\)

Area of copper rod,   A_o = 10 m²
Changes of Area of cross section,
Initial temperature \(\Delta \mathrm{A} =11 -10 =1 \mathrm{~m}^{2}  \)
\(\mathrm{~T}_{1} =90 \mathrm{~K}  \)
\(a_{\mathrm{A}} =0.0021 / \mathrm{K}  \)
\(\mathrm{T}_{2} =?  \)
\(\frac{\Delta A}{A_{0}} =a_{\mathrm{A}} \Delta \mathrm{T}  \)
\(\frac{1 }{10 } =0.0021\left[\mathrm{~T}_{2}-90\right]  \)
\(0.1 =0.0021\left[\mathrm{~T}_{2}-90\right]=\frac{0.1}{0.0021}+90=\mathrm{T}_{2}  \)
\(\mathrm{~T}_{2} =137.61 \mathrm{~K}\)
So the final temperature of a copper rod is 137.61 K

\(\text {Given } m_{1} : m_{2}=3: 4  \)          
\(a_{2} =12 \mathrm{~m} \mathrm{~s}^{-2}  \)
\(a_{1} =?\)
Using Newton's second law,
\(\mathrm{F} =\mathrm{m \times a}  \)
\(\mathrm{F} =\mathrm{m}_{1} \times a_{1}=3 a_{1}  \)
\(\mathrm{~F} =\mathrm{m}_{2} \times a_{2}=4 \times 12=48 \mathrm{~N}  \)
\(3 a_{1} =48  \)
\(a_{1} =48 / 3=16 \mathrm{~m} \mathrm{~s}^{-2}  \)
\(a_{1} =16 \mathrm{~ms}^{-2}\)
The acceleration produced on the other body is \(16 \mathrm{~m} \mathrm{~s}^{-2}\).

(i) Light is a form of energy.
(ii) Light always travels along a straight line.
(iii) Light does not need any medium for its propagation. It can even travel through vacuum.
(iv) The speed of light in vacuum or air is, c = 3 x 10⁸ m/s
(v) Since, light is in the form of waves, it is characterized by a wavelength (λ) and a frequency (v), which are related by the following equation: c = v λ (c - velocity of light).

A human brain is formed of three main parts:
(a) forebrain
(b) midbrain and
(c) hindbrain.
(1) Forebrain:
A. Cerebrum(cortex)
B. Diencephalon
i) Thalamus ii) Hypothalamus
(2) Midbrain
(3) Hindbrain:
A. Cerebellum
B. Pons
C. Medulla Oblongata

a) MgSO₄.7H₂O is heating process:
(i) Magnesium Sulphate heptahydrate or Epsom salt MgSO₄.7H₂O water of crystallization is 7.
(ii) When magnesium sulphate heptahydrate crystals are gently heated, it loses seven water molecules, and becomes anhydrous magnesium sulphate.

(iii) If you add few drops of water or allow it to cool, the colourless anhydrous salt again turns back into hydrated salt.
b) Solubility:
b) Solubility is defined as the number of grams of a solute that can be dissolved in 100g of a solvent to form its saturated solution at a given temperature and pressure.
Solubility = \(\frac{Mass \ of \ the \ solute}{Mass \ of \ the \ solvent}\) x 100

(i) Copper gets covered with a green layer of basic copper carbonate in the presence of CO₂ and moisture.
(ii) \(2 \mathrm{Cu}+\mathrm{O}_{2}+\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{CuCO}_{3} \cdot \mathrm{Cu}(\mathrm{OH})_{2}\)
(iii) Copper reacts with con. \(\mathrm{H}_{2} \mathrm{SO}_{4}\) to from copper sulphate and SO₂.
(iv)  \(\mathrm{Cu}+2 \mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{CuSO}_{4}+\mathrm{SO}_{2} \uparrow+2 \mathrm{H}_{2} \mathrm{O}\)
(v)  So, A is-Copper (Cu)
\(\mathrm{B}\ is \ -\mathrm{CuCO}_{3} \cdot \mathrm{Cu}(\mathrm{OH})_{2}\) Basic copper carbonate.
\(\mathrm{C}\ is \ -\mathrm{CuSO}_{4}\) (copper sulphate)
\(\mathrm{D}\ is \ -\mathrm{SO}_{2}\) (Sulphur oxide)

(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) This law helps us to measure the amount of force. So it is called as law of force'
(iii) Let, "m" be the mass of a moving body, moving along a straight line with an initial speed 'u'.
(iv) After a time interval of 't', the velocity of the body changes to 'v' due to the impact of an unbalanced external force F.
Initial momentum of the body, \( P_{i}=m u \)
Final momentum of the body, \( P_{f}=m v \)
Change in momentum, \( \Delta \mathrm{p}=\mathrm{P}_{\mathrm{f}}-\mathrm{P}_{\mathrm{i}} \)
\(=m v-m u \)
By Newton's second law of motion,
\(\text {Force, } \ F \propto\) rate of change of momentum
\(\mathrm{F} \propto \) change in momentum / time
\(\mathrm{F} \propto \frac{\mathrm{mv}-\mathrm{mu}}{\mathrm{t}}\)
\(\mathrm{F}=\frac{\mathrm{km}(\mathrm{v}-\mathrm{u})}{\mathrm{t}}\)
Here, k is the proportionality constant.
k = 1 in all system of units. Hence,
\(F=\cfrac { m(v-u) }{ t } \)
Since acceleration = change in velocity / time, a = (v-u) / t. Hence, we have
F = m x a
Force = mass x acceleration

R = m (g + a) (R ⟶ Apparent weight)
mg = 50 N
ma = 50 N
R = mg + ma = 50 + 50
R = 100 N
Here Apparent weight (R) is greater than the actual weight mg (=W).

Gibberellin induces parthenocarpy in tomatoes.

Every year May 28 is observed as menstrual hygiene day.

RBCs are biconcave and disc - shaped.

(i) A solution is a homogeneous mixture of two or more substances.
E g: Sea water.
(ii) In a solution, the component present in lesser amount by weight is called a solute.
(iii) The component present in a larger amount by weight is called a solvent.
(iv) Solute + Solvent → Solution

Anaerobic respiration is a process by which carbohydrates are converted into ethyl alcohol.

Hydrogen chloride (HCl), Hydrogen iodide (HI) are two examples for heterodiatomic molecules.

(i) Co-efficient of apparent expansion is defined as the ratio of the apparent rise in the volume of the liquid per degree rise in temperature to its unit volume.
(ii) Its SI unit is K^-1.

When a beam of white light or composite light is refracted through any transparent media such as glass or water, it is split into its component colours. This phenomenon is called as dispersion of light.

(i) Vegetative cell degenerates and the generative cell divides to form two sperms (or male gametes)
(ii) Tip of pollen tube bursts and the two sperms enter the embryo sac.
(iii) One sperm fuses with the egg (syngamy) and forms a diploid zygote.
(iv) The other sperm fuses with the secondary nucleus (Triple fusion) to form the primary endosperm nucleus which is triploid in nature.
(v) Since two types of fusion syngamy and triple fusion take place in an embryo sac the process is termed as double fertilization.
(vi) After triple fusion, primary endosperm nucleus develops into an endosperm.
(v) Endosperm provides food to the developing embryo.
(vi) The purpose of carrying two gametes is one is to form zygote another is to form endosperm to provide food to the developing embryo.

(i) 'A' is copper sulphate pentahydrate (CuSO₄.5H₂O).
(ii) 'B' is Anhydrous copper sulphate (CuSO₄)

i) 1 mole of calcium carbonate are involved
ii) Gram molecular mass of \(\mathrm{CaCO}_{3} \rightarrow \mathrm{Ca} \times 1+\mathrm{C} \times 1+\mathrm{O} \times 3\)
40 x 1 + 12 x 1 + 16 x 3 
40 + 12 + 48 = 100 g
Gram molecular mass of CaCO₃ is 100 g / mol.
iii) 1 mole of CO₂ are there in above equation.

(i) Slime glands are present in the body wall. Their secretion keeps the body moist and slippery so that the host can't remove it easily while it sucks  blood.
(ii) The availability of the host to the leeches is not regular. Hence, a large amount of blood is stored in the crop whenever it gets food. Digestion is also very slow.
(iii) It may take more than a year for the complete digestion after a full meal.
(iv) In leech the ingested blood is stored in crop chambers. It may take more than a year for the complete digestion and absorption of a full meal. So there is no need for an elaborate secretion of digestion juices and enzymes.