CBSE Class 8 Science:
This is a syllabus of elementary standard 8th in CBSE. This covers various topics such as
- The world of living
- Moving things, people and ideas
- How things work?
- Natural Phenomena
This covers various topics under “Food” such as crop production, basic practices in crop production, preparation of soil for cultivation, selection of seeds and sowing techniques, importance of manures and fertilizers, process of irrigation, weeding, harvesting and its importance, methods of storage of water for irrigation, food from animals, microorganisms, etc.
Generally, Agriculture is the cultivation of crops to provide food for all life forms. For such cultivation, soil must be replenished with the nourished manures and fertilizers which can help the seeds to germinate and grow into saplings. Also, enough amounts of other nutrients and water must be supplied at the regular intervals.
The proper water supply to the plants according to its type and the season is called as irrigation. There are two types of irrigation such as Traditional irrigation and modern irrigation. Traditional irrigation is the standard method which is done with the help of human labors and animals. This is one of the cheapest irrigation methods which are done with the help of chain pump, moat and rahat. Modern irrigation method is a modern method of supplying water to the crops at the regular interval. This requires solar power or bio gas to automatically sprinkle water to the crops without any wastage.
How to protect the crop?
Crops are prone to the attacks of pests and insects. Thus, it is necessary to take required steps to protect the crop at the right time. Insects are the six leg organisms which cause heavy loss to the crops whereas pests are the organisms which cause diseases in crop plants. These can be controlled by spraying insecticides and pesticides which can prevent crops from such pests and insects.
The process of removing waste plants is called as weeding. Weeds If present always compete with the healthy crops in obtaining water, sunlight and nutrients. Thus, it is necessary to remove the weeds or unnecessary crops. Weeding can either be done manually by using harrow before they produce flowers and seeds or it can be tilled along with the soil to kill them. Weeds can also be destroyed by using weedicides which are poisonous to the human beings.
The process of cutting the mature crop to gather the grains is called as harvesting. This can either be done manually by using a sickle or using a harvestor.
It is the process of separating the grains from the straw and chaff. A machine called thresher is used for this purpose.
It is the process of natural wind to flow through the grains so that the lighter substances fly away allowing heavier substance falling to the ground.
Breeding and rearing living organisms like cow, goat for the food and other products from them. For example dairy products, poultry farming, pisiculture, sericulture, piggery, etc.,
- Give two examples for each type of crops:
- Kharif crop:
- Rabi crop:
- Maize and paddy
- Wheat and pea
- Name the microorganism which can fix the atmospheric nitrogen in the soil.
Answer: Rhizobium, azatobactor, Blue green algae, etc.
This covers various topics such as Synthetic fibers and plastics, metals and non metals, coal and petroleum, combustion and flame, etc.
Synthetic fibers and plastics:
There are different types of fibers available such natural and synthetic fibers. Cotton is a natural fiber which is obtained from the cotton plant whereas synthetic fibers are the man-made fibers which are prepared by the many raw materials such as petrochemicals. Synthetic fibers are made up of many small units which combine to form large unit called as a polymer. Plastics are the polymers which consist of very long molecules each composed of carbon atoms linked in chains.
Metals and non-metals:
Metals are hard, strong and durable which is made used in many machineries, trains, automobiles, aeroplanes, water boiler, etc., However not all metals are hard and strong. Sodium and potassium are soft metals which can be cut with a knife whereas mercury is a liquid. Metals are very good conductors of heat. Non metals exist in three states such as solids, liquids and gas. Non metals do not conduct electricity and heat except graphite.
Coal and petroleum:
Animals and plants are drifted down to the earth after their death and decomposed to form peat. Coal was formed due to the compression of peat at high temperature and pressure. Coal is the world’s most abundant fossil fuel. Petroleum is formed from the compressed organic matter which is a dark and oily liquid with an unpleasant odour. As petroleum is lighter than that of water, the deposits of petroleum occur above the water level.
Combustion and flame:
Combustion is a chemical process which gives off heat when reacting with oxygen. Such substances are called as combustible substances. Example of such substances are LPG, Kerosene, petrol, etc. There are three types of combustion such as rapid combustion, spontaneous combustion and explosion. The substances which vaporizes while burning produced flames. Kerosene oil and molten wax are the substances that give flame while burning. There are two types of flames such as luminous flames and non-luminous flames.
- Name the petroleum product which can surface the road.
- List the conditions under which combustion can take place?
Answer: Inflammable substance, ignition temperature and Air
- The world of living:
These covers the topics such as conservation of plants and animals, cell structure and functions, reproduction in animals, etc.
Conservation of plants and animals:
Conservation of forest refers to the prevention and maintenance of animals and plants species and protecting them from various threats. Forest can be conserved by maintaining biosphere reserves, wild life sanctuaries, national and zoological parks and botanical gardens.
Cell structure and function:
Cell is a structural and functional unit of all living organisms. Every cell in the body is meant to have some basic function. For example, alveolar is an example of single cell. A group of cells which combine to perform similar function is said to be a tissue. A structure of the cell is made up of cell wall, cell membrane, cytoplasm, and the cell organelles.
This is present in the structure of a plant cell which gives basic strength and rigidity to the plant body and stands erect during all environmental conditions.
This is a biological membrane which separates interior of the cells from the outside environment.
It is a jelly like fluid which is present between the nucleus and cell membrane. Cytoplasm is a site of protein synthesis. Almost all metabolic reactions take place in cytoplasm.
These are the living structures which float in the cytoplasm of a cell.
Reproduction in animals:
This chapter widely covers the topics such as sexual and asexual reproduction in animals, Oviparous and viviparous animals.
Sexual and asexual reproduction in animals:
Reproduction is a process of developing own species. This can take place in all living organisms such as humans, animals and plants. There are two types of reproduction. They are sexual and asexual reproduction.
This type of reproduction involves two organisms such as male and female. Reproductive organs of female produces egg (ovum) whereas the male reproductive organs produce sperm. A zygote is the future individual formed by the fusion of egg and sperm.
This is a type of reproduction where single parent gives rise to the offspring. Animals reproduce asexually by different process such as binary fission, budding, regeneration, cloning and fragmentation.
Oviparous and viviparous animals:
Oviparous animals are the animals which can lay eggs. For example: Hen, Frog, Fish, etc., These types of animals undergo external fertilization.
Viviparous animals are the animals which give birth to the young ones. For example, Lion, cat and humans. These types of animals undergo internal fertilization.
- A place where animals are protected in their natural habitats is called as ________
Answer: Wild life sanctuary
- Where does the internal fertilization occur in humans?
Answer: Female body
- Moving things, ideas and people:
This chapter covers various topics such as force, pressure, friction and sound. Let’s check one by one.
An interaction of one object with the other object results in force between two objects. Force has both magnitude and direction. The SI unit of force is Newton.
Thrust which is a force acted on an object (perpendicular to its surface) acting per unit surface area is called as pressure. The SI unit of pressure is Newton per square meter. (N/m2).
Friction is a type of force which opposes the relative motion between two surfaces of objects in contact.
Sound is a form of energy which causes sensation of hearing. Sound can be heard from all possible objects around us. They are produced from the vibrations caused in the object.
- Give an example of a situation in which applied force causes a change in the shape of an object.
Answer: Inflated balloon
- Sound can travel through _______
Answer: Air, liquids and solids
- How things work?
This chapter covers topics such as conductivity of liquids and chemical effect of electric current.
Conductivity of liquids:
Materials through which electric current can pass is called as conductors. Those materials which pass electric current through them are called as good conductors of electricity whereas those materials which do not allow electric current to pass through them are called as bad conductor of electricity.
Pure water or distilled water is a poor conductor of electricity but if any impurities present in the water, it turns to good conductor of electricity.
Chemical effect of electric current:
When an electric current is passed through a conducting solution chemical reactions are formed. This is known as chemical effect of electric current. Examples of chemical effects of electric current are:
- Formation of bubbles of gas on the electrodes
- Change in the color of solutions
- Deposition of metals in electrodes
- When the free ends of the tester are dipped into the solution, the magnetic needle shows the deflection. Why is it so?
Answer: It is because the solution conducts electricity and the solution plays the rule of the cell.
- Which of the following cannot be easily charged by friction?
- A plastic scale
- A woolen cloth
- An inflated balloon
- A Copper rod
Answer: A copper rod
- Natural Phenomena:
This covers the topic such as Lighting, protection from lightning, earthquakes, etc.,
Lightning is occurred when friction occurs between water and droplets found in the atmosphere. In other words, lightning is cause due to the heavy electric discharge from the clouds to the earth.
A sudden violent shaking of the ground which causes great disaster to the earth.
- Which of the following is not a green gas?
- Carbon dioxide
- Sulphur dioxide
Answer: Sulphur dioxide
- State the laws of reflection?
Answer: The angle of incident is equal to the angle of reflection. The ray of incidence, the ray of reflection and the normal point of incidence lie in the same plane.
Thus, the above are the topics which are covered under the CBSE Class 8 Science.