(i) The blanket of air that surrounds the Earth is called the atmosphere.
(ii) It is held close to the earth by gravitational attraction.
(iii) Atmosphere plays on important role in predicting weather phenomenon.
(iv) It is a mixture of gases, water vapour and dust particles in different proportion.

(i) Weathering is the disintegration and decomposition of materials of the earth's crust by their exposure to atmosphere.
(ii) The nature and magnitude of weathering differs from place to place and region to region.

1. In Megalithic period people buried the dead bodies with grave goods in the cists.
2. Urns or pottery jars were used for burning the dead and also they used sarcophagi made of terracotta.
3. Dolmens, table like stone structures were erected as funerary monuments. Menhirs pillar are like stones erected as part of the burials or memorials.
4. Port holes are holes found in the cists and dolmens on one side.

Merits:
(i) In a huge population country all the people can be represented by multiple parties.
(ii) Particular groups can form their own parties.
(iii) People will have multiple options to vote.
Demerits:
(i) Votes will be scattered.
(ii) It will develop groupsism.
(iii) When there is absolute majority there will be coalition government.

(i) In democracy Fundamenta! Rights are safeguarded to all the people.
(ii) All the People have equal rights.
(iii) People from all walks of life are treated equally.
(iv) People can elect their own leader.

(i) The river channels of the upper course has more energy gradiant then the channels of lower course.
(ii) As the river flows in the lower course it corrodes sideways and makes it wider.

1. The writing of Egyptians were called hieroglyphic.
2. This form of writing used a pictogram based system.
3. Hieroglyphic was used in inscriptions on seals and other objects.
4. Many texts and books were written using this script.
5. The Egyptian writing system was deciphered by the French scholar Franco is Champollion cuneiform.
6. Cuneiform is the Sumerian writing system.
7. The shape of the letter is in the form of wedge and hence it is called cuneiform
8. It is one of the earliest scripts of the world.
9. The epic of Gilgamesh was written in this script.
10 The Sumerians used this script for commercial transactions and writing letters and stories.
11. The clay tablets contain loads of information on the Sumerian civilisation.

The outer surface and inner core of the Earth are totally different in their nature and structure. The structure of the Earth's interior is divided into three layers namely the crust, the mantle and the core.
Crust: Crust is the outer layer of the Earth, where we live. It is the skin of our Earth, which ranges between 5 to 30 km. It is the solid and rigid layer of the Earth. The thickness of the crust is greater below the continents than the ocean floor. The crust is classified as continental crust and oceanic crust. The major elements of crust are Silica (Si) and Aluminium (AI) and thus, it is termed as SIAL.
Mantle: The interior part beneath the crust is called mantle, which is about 2,900 km thick. The major elements of the mantle are Silica (Si) and Magnesium (Mg) and hence it is also termed as SIMA. In the upper part of the mantle. the rock remains solid, whereas, in the lower part of the mantle, rocks are in molten form. This molten rock inside the Earth is called 'magma'.
Core: The core is the innermost and hottest layer of the Earth which lies below the mantle. It is composed mainly of Nickel (Ni) and Iron (Fe). Hence it is called NIFE.
The core is divided into Solid inner core and Liquid outer core. The presence of large quantities of iron in the core is responsible for the Earth's gravitational force. As the Earth rotates on its axis, the liquid outer core spins over the solid inner core and generates the Earth's magnetic field. This is responsible for the functioning of the magnetic compass. Due to high pressure, the materials in the inner core are unable to move and hence remain solid.

a)

b)

c)

(i) Solar power is the conversion of energy from sunlight into electricity either directly using photovoltaic cells or indirectly using concentrated solar power.
(ii) Solar panels absorb the sunlight as a source of energy to generate electricity.
(iii) A solar electric system can reliably produce electricity for our home and offices.