Planets
We have studied about the planets of our solar system in previous classes. We will study only these four planets here.
Mercury
It is named after the name of the messenger of the Roman gods. Mercury takes 58 days to spin on its axis and 88 days to revolve around the Sun. There is no atmosphere and water on this planet. It is covered in craters. The biggest craters on this planet is calories basin.
Venus
It is named after the Roman goddess of love and beauty. It is the most beautiful object in the sky. This planet was first observed by Galileo. Venus is the brightest and hottest planet, because it has atmosphere to trap the sun's light making it hottest, it is called as the morning and evening star. Venus rotates on its axis very slowly but it revolves around the sun fast and hence 1 day on Venus = 243 earth days.
But 1 year on Venus = 225 earth days. It has no moon.
Earth
The only planet in the solar system that has life. It has all the essential components of life i.e.
Appropriate warmth from the Sun;
Water, about 71 % of the surface is covered with water;
Oxygen
The first life on the earth appeared about 3 billions years ago. It is also named after Roman goddess "Terra" meaning earth. The temperature of the earth's surface is 60°c and it increases as one goes deeper and deeper.
Earth is magnetic because of the presence of molten iron in the core. The needle of the compass always points towards the magnetic north pole.
The earth rotates on its axis in approximately 23 hours, 56 minutes and 22.7 seconds. It revolves around the sun in 365 days, 6 hours, 9 minutes and 10 seconds.
Object on this planet doesn't fly off because of the force of gravity, which pulls every object towards itself.
Gravitation
Every planet in the universe attracts each other with a force proportional to their mass. The earth attracts the object when thrown upwards due to the force of gravity. The force of attraction of the earth is due to the structure of the earth’s core.
Why does all objects fall towards the earth instead of going up?
Why do we feel being pulled down when we jump?
Why it is easier to fail than to jump?
The answer lies in this fact that there is something in the earth which tries all the time to pull all the objects towards itself-
This something in the Earth is called as gravity or more... 
Other Heavenly Bodies
Asteroid
Large number of small bodies that fills the gap between the orbits of the Mars and Jupiter and revolve around the Sun like other planets. Asteroids are called as minor planets because it has its own orbit and its size varies from kilometer to few hundred kilometers. About 3500 asteroids are orbiting the Sun.
Comets
They are very small sized celestial bodies made up of balls of ice and rock and revolve around the Sun. They become visible to us only when come closer to the Earth. They usually have a small head and a glowing tail of gas. The size of the tail increases as it approaches the Sun. Tail disappears as it moves away from the Sun. Halley's comet appears after nearly 76 years, last time it was seen in 1986-
Meteors and Meteorites
Meteor is called a shooting star. it is small stone like objects revolving around the Sun. Its presence can be felt only when it enters the earth's atmosphere
Because of too much heat production meteors start to glow, and get: evaporated within a short time.
Meteorites are part of large meteors, that reaches the surface before they gets evaporated.
Which one of the following statements is correct?
(a) Asteroids are the part of our solar system
(b) Asteroids are not the part of our solar system
(c) Asteroids are the satellites of planet saturn
(d) Asteroids are the satellites of planet venus
(e) None of these
Answer: (a)
Explanation
Asteroids are the part of our solar system. Therefore, option (A) is correct and rest of the options is incorrect,
Which one of the following statements is correct about comet?
(a) Comet revolves around the sun
(b) Comet is a part of our solar system
(c) A comet has many moon
(d) Both A and B
(e) None of these
Answer: (d)
Explanation
Comets are part of our solar system which revolves around the sun. Therefore, option (D) is correct and rest of the options is incorrect.
Constellation
If we see night sky, we find certain patterns of stars resembling living creatures or inanimate objects. Such groups of stars are called as constellation. Each constellation is named after their resemblance more... 
Reproduction
Reproduction is the process of producing offspring of its own kind. For example an apple tree can produce another apple tree only, it can't produce mango tree.
Vegetative reproduction is a type of asexual reproduction in which new plant is generated from the vegetative part of the plants i.e. stems, roots, leaves etc.
Vegetative reproduction by Stem
Runnerss
Reproduction in strawberry
Stems, which run horizontally parallel to the ground. New roots emerge from the nodes, thus gives rise to new plants e.g. lawn grass, strawberries etc.
Suckers
Vegetative reproduction in mint
The reproduction is very similar to runners but have shorter internodes, e.g. mints, chrysanthemum.
Reproduction in ginger by rhizome
It has underground nodes and internodes. Axillary buds are present on the nodes, which develop into new plants on getting favorable conditions, e.g. ginger.
Tuber
Vegetative reproduction in potato
Potato is a tuber that has bud, which is capable of producing new plant.
Corn
Corm is a condensed form of rhizome, which is formed vertically in the ground. A single corm develops new plant e.g. colocasia
Reproduction in colocasia
Bulbs
A type of plants which has bulbs for the storage of food for helping them in non favorable condition. The bud in the plants grows into new plants, e.g. onion, lily, etc,
Vegetative Reproduction by Leaf
Adventitious Buds
Buds present on the margin of leaves, which develops into new plants on getting the favorable condition.
Vegetative Reproduction by Roots
Vegetative reproduction in a plant is the asexual reproduction. Tuberous roots of sweet potato and dahlia when get detached from the plant grow into new plant.
Vegetative reproduction by roots
Uses of crops
Medicinal plants
more... 
Rock Cycle
The rock cycle involves the formation, alteration by weathering and then formation of rock again. All the process occurs simultaneously.
Weathering of Rocks
Weathering of rocks takes long time. After weathering, rocks are converted into soil.
1. Strong desert winds 2. Flowing water
3. Ocean tides 4. Glaciers
Mineral
A mineral is composed of an element or a chemical combination of elements. For example, Silica is a mineral made up of oxygen, silicon and a small amount of other elements.
Gemstone is a naturally occurring beautiful and attractive mineral which has immense demand in jewellery making. These minerals are cut and polished for making the jewellery.
Recycling of Minerals
Useful minerals are not in huge quantity. They are available in limited quantity hence they are recycled from scrap.
Metals can be recycled again and again from scrap without degradation of its properties.
Uses of Mineral
Difference between mineral and Rock
| Mineral | Rock | ||||||||||||||||||||||||||||
| Pure in state | Contain more than 1 mineral | ||||||||||||||||||||||||||||
| Look attractive | Not attractive | ||||||||||||||||||||||||||||
more...
 Rocks and Minerals
Lithosphere Lithosphere of the earth mainly consists of rocks and soil. Rocks and soil both are natural resources. Rocks are made up of grains called minerals. One or more than one minerals are present in one kind of rock. Minerals can be seen or can't be seen with the naked eyes. Minerals are very important natural resource as they contain ores, from which metals and non-metals can be obtained profitably.
 Types of Rocks
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Soil Erosion
Removal of the top fertile layer of the soil due to weathering is called soil erosion. Heavy rain fall and wind are the cause of soil erosion.
Soil Erosion by Wind
Particles from the top layer of the soil are lifted up by the Wind to carry it to some other place. This type of erosion of soil generally occurs in arid regions with little vegetation or no vegetation.
Deforestation causes desertification
Deep ploughing makes the soil very loose
We can reduce soil erosion by planting trees as the roots of the plants hold the top fertile layer of the soil firmly.
Embankment reduces the speed of water waves
Soil
Soil is the uppermost layer of the earth's surface which is made up of the particles of rocks, humus, air and water. Soil contains nutrients and water for the survival of plants. The product, after the process of photosynthesis is glucose, which is made by the plant in the presence of carbon dioxide and Sun rays. The leaves of the plant trap Sun rays and carbon dioxide from the atmosphere. The other necessary nutrients such as, water and minerals are absorbed by the root from the soil. Therefore, the growth of the plant depends on the quality of soil.
Formation of Soil
Soil is formed from rocks by weathering. Rocks are broken down into small pieces due to heat of the Sun, wind, snow, rain and natural events like earthquakes to form soil. Soil formation as well as fossil fuel formation is a very slow process. It takes millions of years to form particles of soil from rocks. Roots of few plants can also break rocks by penetrating deep into the space of rocks.
Weathering of rocks due to flowing water
Top soil or A-horizon is dark in colour and rich in minerals and humus. This layer is soft, porous and can retain water. Plants grow in this layer. This layer is beneficial for worms, beetles, rabbit, rats and moles as it provides shelter to these organisms. Sub soil or B horizon lies below the top soil. It is grey or red in color. It is comparatively harder and made up of hard broken pieces of rocks. A type of rock which is called Bed rock is found below the surface of the earth. Bed rock consists of hard non porous rocks.
Separation of mixture
LIQUID 
The above mentioned examples are physical change that can be brought back either by giving or loosing heat- Physical change is reversible. Burning of paper is a chemical change as ash can't be brought back to paper by any means. Chemical change is irreversible.
Rusting of Iron Burning Paper
Growth from an infant to an adult is an irreversible change.
Which of the following plays an important role In the process of changing one state of matter into another?
(a) Heat
(b) Volume
(c) Mass
(d) Density
(e) None of these
Answer: (a)
Explanation
One state of matter is converted into another form either by taking or releasing heat energy. Therefore, option (a) is correct and rest of the options is incorrect.
Which one of the following is an example of liquid state of matter?
(a) Air
(b) Soil
(c) Water
(d) All of these
(e) None of these
Answer; (c)
Explanation
Water is an example of liquid stale of matter. Therefore, option (c) is correct and rest of the options is incorrect. 
Introduction
Everything, which we see around us is called the matter. Matter is made up of atoms and atoms are made up of electrons, protons, and neutrons. There are three states of matter, solid, liquid and gas. The properties of solid, liquid and gas states of a same matter are different. The atoms in the solid are tightly packed in comparison to the structure of atoms in liquid and gas. In this chapter, we will study about the properties of different types of matter.
Properties of Three States of Matter
