Q1. State the effects of force.
Answer: Force may:
➀ make an object move from rest.
➁ change the speed of a moving object.
➂ change the direction of motion of an object.
➃ change the shape of an object.
➄ stop a moving object
Q2. Calculate the pressure exerted by a force of 100 N on an area of 4 m²
Fill in the blanks with suitable words.
1. ________ gas in air is essential for combustion.
2. A chemical process in which a substance reacts with oxygen to give off heat is called __________.
3. During the process of combustion, _______ and light are given out.
Q1: In general, oxides of non metals are ________ in nature?
(a) basic
(b) acidic
(c) neutral
(d) amphoteric
Q2: The percentage of which of the following components of air always varies from one place to the other?
(a) O₂
(b) N₂
(c) Water vapour
(d) CO₂
Fill in the blanks with suitable words.
1. The period of life, when the body undergoes certain noticeable changes, leading to reproductive maturity is called __________.
2 _______ is the start of the time when a boy is biologically ready to become a father and a girl is ready to become a mother.
3. ______ are thread-like structures in the nucleus carrying genetic information.
Q1: All metals are solids except:
(a) Sodium
(b) Calcium
(c) Mercury
(d) Copper
Q2: Which of the following metal does not react with dilute Hydrochloric acid?
(a) Iron
(b) Sodium
(c) Magnesium
(d) Copper
Fill in the blanks with suitable words:
1. The stars, the planets, the moon and many other objects in the sky are called _________ objects.
2. The various shapes of the bright part of the moon as seen during a month are called ________ of the moon.
3. The moon is visible due to reflected ________.
Fill in the blanks with suitable words.
1. _________ are the substances obtained from petroleum and natural gas.
2. Petroleum is obtained from dead remains of living organisms, that is why it is called a ________ fuel.
3. Kerosene is used in ______ aircrafts.
4. In India, ________ gas has been found in Tripura, Rajasthan, Maharashtra and in the Krishna Godavari delta.
Fill in the blanks with suitable words:
1. Cultivation of plants and rearing of animals for food and other beneficial items is called ____________.
2. When plants of the same kind are grown and cultivated at one place on a large scale, it is called a ________.
3. The process of loosening and turning of the soil is called _________ or _________.
Q1: What is a plastic?
Answer: Plastic is also a polymer like the synthetic fibre. All plastics do not have the same arrangement of units. In some, it is linear, whereas in others it is cross-linked.
Q2: What are the main properties of plastics?
Answer:
① Plastic is easily mouldable in all types of possible shapes.
② Most plastics are light, chemically stable and do not rust. The weight of plastic is less when compared to that of metal.
③ Some types of plastics are good insulaters and have low thermal conductivity.
④ Plastic can be recycled, coloured, reused, rolled into sheets or made into wires.
⑤ Most plastics have poor heat resistance.
⑥ Plastics have good durability (lasts longer).
CBSE Class 8 - Science - Conservation of Plants and Animals (Worksheet)
Directions: Fill in the blanks with suitable words:
1. Plants and animals of a particular area are known as the _________ and __________ of that area.
2. Red Data Book contains a record of __________ species.
3. _________ is the restocking of destroyed forests by planting new trees.
