Class 8 Science Sample Paper - 5 Class 8 Notes | EduRev

Science Class 8

Created by: Dr Manju Sen

Class 8 : Class 8 Science Sample Paper - 5 Class 8 Notes | EduRev

The document Class 8 Science Sample Paper - 5 Class 8 Notes | EduRev is a part of the Class 8 Course Science Class 8.
All you need of Class 8 at this link: Class 8

Ques 1: Choose the correct option:
(i) Which of the following is not likely to cause Tsunami?

(A) A major nuclear explosion under sea
(B) Earthquake
(C) Volcanic eruption
(D) Lightning
Ans: D

Ques 2: Choose the correct option:
(ii) Which of the following statements is correct regarding rods and cones in the human eye?

(A) Cones are sensitive to dim light
(B) Cones are sensitive to bright light
(C) Rods are sensitive to bright light
(D) Rods can sense colour.
Ans: B

Ques 3: Choose the correct option:
(iii) Which of the following is NOT a planet of the sun?

(A) Sirius
(B) Mercury
(C) Saturn
(D) Earth
Ans: A

Ques 4: Choose the correct option:
(vi) Which of the following is not a source of air pollution?

A) automobile exhaust
B) burning of firewood
C) Wind mill
D) power plant
Ans: C

Ques 5: Choose the correct option:
(v) Which of the following is not a traditional method of irrigation?

(A) Moat
(B) Chain pump
(C) Drip system
(D) Rehat
Ans: C

Ques 6: Choose the correct option:
(vi) Which of the following is an antibiotic?

(A) Sodium bicarbonate
(B) Streptomycin
(C) Alcohol
(D) Yeast
Ans: B

Ques 7: Choose the correct option:
(vii) Typhoid is a________ disease.

(A) protozoan
(B) viral
(C) bacterial
(D) fungal
Ans: C

Ques 8: Choose the correct option:
(viii) The most suitable material for the preparation of handles of cooking utensils is

(A) Polythene
(B) PVC
(C) Nylon
(D) Bakelite
Ans: D

Ques 9: Choose the correct option:
(ix) Which of the following can be beaten into their sheets?

(A) Zinc
(B) Phosphorus
(C) Sulphur
(D) Oxygen
Ans: A

Ques 10: Choose the correct option:
(x) PCRA stands for

(A) Public Conservation Research Association
(B) Petroleum Conservation Research Association
(C) Public Council of Research Association
(D) Partial Counting of Remaining Amendment
Ans: B

Ques 11: (i) What is Teflon?
Ans: (i) Teflon is a special plastic on which oil and water do not stick. It is used for non-stick coating in cooking wares.

Ques 12: (ii) Why is phosphorus stored in water?
Ans: (ii) Phosphorus is a very reactive non-metal. It catches fire if exposed to air. So, it is stored in water to prevent it in contact with atmospheric oxygen.

Ques 13: (iii) Name the slow process which involves the conversion of dead vegetation into coal.
Ans: (iii) Carbonization

Ques 14: (iv) How can we say that fish exhibits external fertilisation?
Ans: (iv) Female fish lay eggs in water while male fish release their sperms in water. Sperms swim and reach the egg of fish, randomly due to water currents and thus external fertilisation occurs.   

Ques 15: (v) What are the interactions of poles of two magnets? 
Ans: (v) (a) Like poles repel each other.      
(b) Unlike poles attract each other.

Ques 16: (vi) Astronauts in outer space have to use radios to communicate with one another. Why?
Ans: (vi) In outer space, there are no gases to help transmit sound. To communicate with one another astronauts make use of electromagnetic waves such as radio waves, which can travel through vacuum.

Ques 17: Why are vaccines so important for children? 
Ans: By introducing vaccine in body, the body fights and kills the bacteria by producing suitable antibodies.  The antibodies remain in the body and the child is protected from the disease causing microbes.

Ques 18: What are thermoset mg plastics? Write two examples with their characteristics.
Ans: There are some plastics which when moulded once, cannot be softened by heating. These are called thermosetting plastics, e.g., Bakelite and melamine. Bakelite: It is a poor conductor of heat and light. Melamine: It is fire resistant.

Ques 19: Where is oil found in India?
Ans: Oil is found in India in Assam, Gujrat and Mumbai High and in the river basin of Godavari and Krishna.

Ques 20: What do you understand by fuel efficiency?
Ans: Fuel efficiency is determined by its calorific value which is the amount of heat energy produced on the complete combustion of 1 kg of a fuel. The calorific value of a fuel is expressed in kJ/kg.

Ques 21: Why are wildlife sanctuaries important for conservation of plants and animals? 
Ans: In a wildlife sanctuary, killing and capturing of wild animals are strictly prohibited. It does not allow any human activity which disturbs the wild animals in their habitat. So, in these areas, animals live in natural environment, protected from people. This is the reason that sanctuaries are important.

Ques 22: What is gene? What is its function?
Ans: Gene is a unit of inheritance in living organisms. It controls the transfer of hereditary characteristics from parents to off springs.

Ques 23: Explain Internal Fertilisation.
Ans: Fertilisation which takes place inside the female body is called internal fertilisation. Internal fertilisation occurs in many animals including cows, dogs and hens.

Ques 24: What is IFV?
Ans: IVF or In-vitro fertilisation. In such cases, doctor collects freshly released egg and sperms and keep them together for a few hours for fertilisation. When fertilisation occurs, the zygote is formed and allowed to develop for about a week and then it is placed in the mother's uterus. Babies produced by this technique is called test tube babies.

Ques 25: A ball rolling along the ground gradually slows down and finally comes to rest. Why does this happen? What is the effect of this force?
Ans: The force responsible for changing the state of motion of ball is the force of friction. The ball will come to rest position. This force causes wear and tear of the objects in motion.

Ques 26: Explain why:
A pencil will write on paper but not on glass.
Ans: 
Due to friction, a pencil writes on paper but as there is smoothness on the surface of glass, a pencil cannot write on glass.

Ques 27: Fill in the blanks with most appropriate answer:            
(a) The fish like baby of a frog_________.
(b) The animal that lay thousands of eggs _________.
(c) The stage of the embryo in which all the body parts can be identified________.

Ans: (a) Tadpole                  
(b) Fish/Lice                  
(c) Foetus

Ques 28: What is the importance of using manure and fertilizers as an agricultural practice?
Ans: Using manure and fertilizers as an agriculture practice is important as continuous growth of crops makes the soil poorer in certain nutrients. These both are added to the soil in the form of nutrients for the healthy growth of plants. Manure replenishes the soil with nutrients and also improves water retaining capacity whereas fertilizers make soil rich in a particular nutrient. They also help farmers to get better yield of crops.

Ques 29: Classify the following into friendly and harmful micro-organisms:
Yeast, malaria parasite, Lactobacillus, bread mould, Rhizobium, Bacillus anthracis.
Ans: 


Friendly micro-orgamsxns

Harmful micro- organisms
(i)
Yeast
(i)
Malarial Parasite
(ii)
Lactobacillus
(ii)
Bread mould
(iii)
Rhizobium
(iii)
Bacillus anthracis


Ques 30: Give few examples to show that plastics are non-corrosive in nature. 
Ans: Corrosion of a substance is the process of reaction with water or moisture of air and getting damaged.
Following are the few examples:
(i) We use buckets and mugs made up of plastics in our bathrooms regularly, but they remain as it is for long time period.
(ii) Plastics do not decompose in atmosphere for long period.
(iii) Many health care products such as packaging of tablets, threads used for stitching wounds, remain in their original look for long time period.

Ques 31: Mercury is the only metal found in liquid state. It is largely used in thermometers to measure the temperature. But mercury is a very dangerous metal as its density is very high. What two precautions would you take while handling the equipment containing mercury?
Ans: Precautions while handling the equipments containing mercury are:
(i) Mercury, a liquid metal with high density, can corrode the skin if it drops over it.
Hence, the vessel should be closed or tightly packed.
(ii) It should not be heated directly,

Ques 32: Write three important uses of non-metals.
Ans: Important uses of non-metals:
(i) Non-metals are essential for our life as all living beings inhale oxygen and breathe out carbon dioxide during breathing.
(ii) They are used in fertilizers to enhance the growth of plants.
(iii) Non-metal is used in the purple coloured solution that is applied on wounds as an antiseptic.
(iv) Non-metals are used in crackers.

Ques 33: What are the advantages of using CNG and LPG as fuels? 
Ans: CNG and LPG are very important fuels because it is easy to transport them through pipes. CNG (Compressed natural gas) and LPG (Liquefied Petroleum gas) are used for power generations and as non-polluting fuels. Its great advantages are that it can be used directly for burning in homes and factories

Ques 34: (a) Which part of the cell contains organelles?
(b) State three differences between plant cell and animal cell.
(c) Where are chromosomes found in the cell?

Ans: (a) Cytoplasm contains all the organelles of the cell. Organelles are the small structures present inside the cell which have their specific structure and specialised functions.
(b)


Plant cell
Animal cell
(i)
Presence of cell wall.
Absence of cell wall.
(ii)
Large size vacuoles are present.
Small size vacuoles are present.
(iii)
Centrioles are absent.
Centrioles are present.
(iv)
Chloroplast (Plastid) is absent.
Chloroplast (Plastid) is present.

(c) Chromosomes are the thread like structures found inside the nucleus; present in the cell.

Ques 35: Read the passage and answer the given question. Sarvesh noticed that during rainy season, the leaves of the plants in his school get burnt. His teacher told him that all this is due to acid rain.
(a) What is acid rain?
(b) What are the harmful effects of acid rain.
(c) What efforts can you do to reduce this acid rain?

Ans: (a) The gases such as sulphur dioxide (SO2) and nitrogen dioxide (NO2) react with water vapor in the atmosphere to form sulphuric acid and nitric acid and constitute the acid rain.                                      
(b) The harmful effects of acid rain are as follows:
(i) It harms the plant life; as leaves and other parts of the plant get burnt
(ii) It corrodes the marbles (CaCO3) of the monuments; which results in its yellowing.
(iii) It affects the animal life also.
(c)  (i) We can use cleaner fuels like LPG and CNG.
(ii) Chimneys should be well equipped with air niters. 

Ques 36: What are contact and non-con tact forces? Explain briefly, with suitable examples.
Ans: Forces can be of two types:
(i) Contact forces.
(ii) Non-contact forces.
(i) Contact forces: The forces that come into play when two objects come in contact with each other.
(a) Muscular force: The force which is exerted due to action of muscles is known as the muscular force, e.g., running, bending, walking etc.
(b) Frictional force: The force responsible for changing the state of motion of an object. Equal and opposite forces are being exerted on an object when its surface comes in contact with other surface, e.g., a car or scooter comes to rest.
(ii) Non-contact forces: The forces that can be exerted from a distance without establishing a contact are called the non-contact forces.
(a) Magnetic force: Force exerted by a magnet on another magnet or magnetic substances like iron is called magnetic force, e.g., Car sticking to an electromagnet.
(b) Electrostatic force: Force exerted by a charged body on another charged body or uncharged body is called electrostatic force, e.g., If we rub a comb with hair and bring it near some small bits of paper, it attracts the bits of paper towards itself. This is electrostatic force.
(c) Force of gravity: The earth pulls every object towards its centre. The force exerted by the earth is called the force of gravity.

Ques 37: Write short notes on the following:
(i) Cytoplasm                            
(ii) Nucleus of a cell

Ans: (i) Cytoplasm: It is a jelly-like substance, present between the cell membrane and the nucleus. It encloses all tiny structures called cell organelles that perform different functions. It also contains water, sugar, proteins, minerals etc.    
(ii) Nucleus of a Cell: It is a spherical component of cell commonly located in the centre of cell. It is covered by porous nuclear membrane and contains genetic material like RNA and DMA. It also contains thread-like structures called chromosomes, which carry genes. Nucleus controls various activities of cell.   

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