Class 8 Science: Chapters 1-6 Review

Comprehensive practice flashcards covering Agricultural Practices, Microorganisms, Synthetic Fibres, Metals/Non-metals, Fossil Fuels, and Combustion based on the provided Science transcript.

When plants of the same kind are cultivated at one place on a large scale, it is called a __________.

crop

What is the typical time period for the rainy season in India during which Kharif crops are sown?

June to September

Give examples of Rabi crops grown in India from October to March.

Wheat, gram, pea, mustard, and linseed

The process of loosening and turning of the soil is called __________ or __________.

tilling or ploughing

Why is the use of a seed drill preferred for sowing?

It sows seeds uniformly at equal distance and depth, ensures they are covered by soil to protect from birds, and saves time and labour.

What is the primary difference between fertilisers and manure regarding their composition?

Fertiliser is a man-made inorganic salt, while manure is a natural substance obtained by the decomposition of cattle dung and plant residues.

What is the role of Rhizobium bacteria in the roots of leguminous plants?

They fix atmospheric nitrogen to replenish the soil.

The supply of water to crops at regular intervals is called __________.

irrigation

Describe the Drip system of irrigation.

A system where water falls drop by drop directly near the roots, ensuring no water is wasted.

The removal of undesirable plants from a field is known as __________.

weeding

What is threshing?

The process of separating the grain seeds from the chaff.

When animals are reared on a large scale with proper food, shelter, and care, it is called __________.

animal husbandry

What are the four major groups of microorganisms?

Bacteria, fungi, protozoa, and some algae

Who discovered fermentation in 1857?

Louis Pasteur

What medicine was prepared from the green mould observed by Alexander Fleming in 1929?

Penicillin

Who discovered the vaccine for smallpox in 1798?

Edward Jenner

Microbial diseases that spread from an infected person to a healthy person through air, water, or food are called __________ diseases.

communicable

Which mosquito acts as the carrier of the malaria parasite (Plasmodium)?

Female Anopheles mosquito

Identify the causative microorganism of Tuberculosis.

Bacteria

What is the process of heating milk to about $70^{\circ}C$ for 15 to 30 seconds and then suddenly chilling it called?

Pasteurisation

Our atmosphere contains approximately __________ nitrogen gas.

$$78 \%$$

Common natural fibre polymers like cotton are made of units called __________.

cellulose

Which synthetic fibre is known as artificial silk?

Rayon

Identify the first fully synthetic fibre made from coal, water, and air in 1931.

Nylon

What is PET an acronym for?

Polyethylene terephthalate

Plastic that deforms easily on heating and can be bent easily is called __________.

thermoplastic

Name two examples of thermosetting plastics.

Bakelite and melamine

What are the 5 R's of the responsible citizen principle?

Reduce, Reuse, Recycle, Recover, and Refuse

The property of metals by which they can be beaten into thin sheets is called __________.

malleability

The property of metal by which it can be drawn into wires is called __________.

ductility

What is the only metal found in a liquid state at room temperature?

Mercury

Generally, metallic oxides are __________ in nature, while non-metallic oxides are __________ in nature.

basic, acidic

Why is sodium stored in kerosene?

Because it is very reactive and reacts vigorously with oxygen and water.

How much nitrogen is found in the Earth's atmosphere?

$$78 \%$$

What are exhaustible natural resources?

Resources present in limited quantities that can be exhausted by human activity, such as coal, petroleum, and natural gas.

The slow process of conversion of dead vegetation into coal is called __________.

carbonisation

What is 'black gold'?

Petroleum, so named due to its great commercial importance.

What does CNG stand for?

Compressed Natural Gas

A chemical process in which a substance reacts with oxygen to give off heat is called __________.

combustion

The lowest temperature at which a substance catches fire is its __________.

ignition temperature

What are the three essential requirements for producing fire?

Fuel, air (oxygen), and heat

Which substance is the best extinguisher for fires involving electrical equipment or petrol?

Carbon dioxide (CO2)

What is the hottest part of a candle flame?

The outer zone of complete combustion (blue zone)

The amount of heat energy produced on complete combustion of $1\,kg$ of a fuel is called its __________.

calorific value

What is the unit for expressing calorific value?

$$kJ\,kg^{-1}$$

The rise in the temperature of the atmosphere of the earth caused by increased carbon dioxide is called __________.

global warming