When lead(II) nitrate is heated, it decomposes into lead (II) oxide, nitrogen dioxide and oxygen. The balanced chemical equation for this reaction is 2 Pb(NO3)2 (s) produces 2 PbO (s) + 4NO2 + O2 (g). Since, the valency of lead is +2 it will need two nitrate radical. Lead nitrate is formed by reacting lead with nitric acid, so by displacement reaction it forms, lead nitrate ,water and nitrigon di oxide. When lead nitrate is heated, it due to thermal decomposition gives out metal oxide, oxygen and nitrogen dioxide.

Land degradation means decrese in the quality of the land .,,such that its nutrients and fertility is lost and is in incapable of growing crops ..the causes of Land degradation are ..
1) Soil pollution
2) Soil Erosion
3) Over grazing
4) Extraction of minerals at a repeated stage..
5) Drought ..

Over irrigation is main cause of land degradation in Punjab due to waterlogging leading to increase in salinity and alkalinity in the soil. Punjab, Haryana, Uttar Pradesh are the states facing issue of land degradation.

Because it contains ions in water which moves to the opposite electrodes when electricity is passed through the solution. this is possible in molten state since the electrostatic forces of attraction between the oppositely charged ions are overcome due to the heat.

"Sustainable development is development that meets the needs of the present, without compromising the ability of future generations to meet their own needs."  To make development sustainable, non renewable sources of energy are to be saved for future use, and care should be taken that the natural resources are not overexploited. Sustainability of development means economic development without any damage to the environment, and keeping in mind the needs of the future.

When the temperature is increased, the atoms of the material vibrate and it makes the valence electrons present in the valence band to shift to the conduction band. This in turn increases the conductivity of the material. When the conductivity of the material increases, it means that the resistivity decreases and so the current flow increases. Thus some insulators at room temperatures changes to conductors at high temperature. For insulators they have a negative temperature co – efficient. So the value of temperature co –efficient of resistivity, α is negative. 

Lencho went out in the rain to feel the rain falling down.  He compared the big drops of rain to new coins. He compared them to coins because the rain indicated a very good and healthy harvest of the year. He was hoping that this year his crops would bring him a lot of money. It is because of this reason that he symbolizes the drops of rain to the coins falling from the sky on him and his family.

Principles of Metallurgy:

The metallurgical process can be classified as the following:

1. Crushing and grinding: The first process in metallurgy is crushing of ores into a fine powder in a crusher or ball mill. This process is known as pulverization.

2. The concentration of ores: The process of removing impurities from ore is known as a concentration of minerals or ore dressing. In metallurgy, we concentrate the ores mainly by the following methods.

3. Hydrolytic method: In this method, we pour the ore over a sloping, vibrating corrugated table with grooves. A jet of water is allowed to flow over the surface. The denser ore particles settle in the grooves, and the impurities are washed away by water.

4. Magnetic separation: In this case, the crushed ore is placed on a conveyor belt. This belt rotates around two wheels in which one of the wheels is magnetic, and therefore the magnetic particles get attracted to the magnetic wheel and fall apart from the non-magnetic particles.

5. Froth floatation: In this process, we take the crushed ore in a large tank which contains oil and water. A current of compressed air is passed through it. The ore gets wet by oil and is separated from the impurities in the form of froth. Ore is lighter, and so it comes on the surface and impurities are left behind.

The process of taking air into and expelling it from the lungs is called breathing.
The action of breathing in and out is due to changes of pressure within the thorax, in comparison with the outside. This action is also known as external respiration. When we inhale the intercostal muscles (between the ribs) and diaphragm contract to expand the chest cavity. The diaphragm flattens and moves downwards and the intercostal muscles move the rib cage upwards and out.

This increase in size decreases the internal air pressure and so air from the outside (at a now higher pressure that inside the thorax) rushes into the lungs to equalise the pressures.

When we exhale the diaphragm and intercostal muscles relax and return to their resting positions. This reduces the size of the thoracic cavity, thereby increasing the pressure and forcing air out of the lungs.

Enzymes are soluble protein molecules that can speed up chemical reactions in cells. These reactions include respiration, photosynthesis and making new proteins. For this reason enzymes are sometimes called biological catalysts.

Oxidation: A chemical reaction which involves addition of oxygen or removal of hydrogen or loss of electron(s) is called as oxidation.
2Mg + O₂ →2MgO (addition of oxygen)
H₂S + Br₂ → 2HBr + S (removal of hydrogen)
Fe²⁺ → Fe³⁺ + e^- (loss of electron)

Given: x² + 32x – 273 = 0
We can rewrite the given equation as 
⇒ x² + 39x - 7x – 273 = 0
⇒ x( x + 39) 7 7(x +39) = 0
⇒ ( x +39)(x - 7) = 0
∴ Factors of the given quadratic equation are  ( x + 39) and (x - 7)

X + y = 5 ( equation 1 )
2x - 3y = 4 ( equation 2 )
Now,
multiplying (eq.1) by 2 and subtracting (eq.2) from ( eq.1 )
(2x + 2y = 10) - (2x - 3y = 4 )
=> 2x + 2y - 2x + 3y = 6
=> 5y = 6
=> y = 6/5
Putting the value of y in ( eq.1 )
=> x+ y = 5
=> x + 6/5 = 5
=> x = 5 - 6/5
=> x = 19/5

X + y = 5 ( equation 1 )
2x - 3y = 4 ( equation 2 )
Now,
multiplying (eq.1) by 2 and subtracting (eq.2) from ( eq.1 )
(2x + 2y = 10) - (2x - 3y = 4 )
=> 2x + 2y - 2x + 3y = 6
=> 5y = 6
=> y = 6/5
Putting the value of y in ( eq.1 )
=> x+ y = 5
=> x + 6/5 = 5
=> x = 5 - 6/5
=> x = 19/5