SCIENCE PRACTICE SHEET -STD 8 WITH ANSWERS

PODAR INTERNATIONAL SCHOOL

Practice Sheet – 2 (2017-18)

Grade: VIII

Subject: Science Answer Scheme

Duration: 1 ½ hours

1 mark questions
1.
What is harvesting?
ans.
The cutting and gathering of crops after they have matured is called harvesting.
(Ch 1: Food Sources and Us, pg 9)
2.
Which plant tissue is responsible for increase in the length of the plant?
ans.
Apical meristems / terminal meristems
(Ch 3: Tissues: Cells in Unison, pg 33)
2 mark questions
3.
Give reasons for the following.
(a)
The use of fertilisers should be controlled.
ans.
The use of fertilisers should be controlled as they can harm the environment.
(Ch 1: Food Sources and Us, pg 5)
(b)
Lysosomes are known as suicidal bags.
ans.
Lysosomes contain substances that help in the digestion of foreign bodies and worn out cell parts.
(Ch 2: Cells- The building blocks of life, pg 21)
4.
(a)
What is the relation between pressure exerted by liquids and its depth?
ans.
The pressure exerted by liquids increases with depth.
(b)
Give any one application of liquid pressure.
ans.
 Water supply tank is placed at a height in buildings because when placed at a height, the pressure of water will be large enough to force the water to reach the taps of the house.
 In the deep sea, the pressure of the water is tremendously high. Hence the body of the submarine is thick and built of strong material.
(any one)
(Ch12: Forces in Action, Pg- 175-176)
CB/VIII/1718 Practice Sheet - 2 page 2 of 5
3 mark questions
5.
Draw a neat labelled diagram of phloem.
ans.
(Ch 3: Tissues: Cells in Unison, pg 35)
6.
Nitya was preparing food in the kitchen. She got call from her friend. While on call, she forgot to turn off the cooking gas. Thus, the food was burnt. Her brother was watching TV in the living room. He sensed some burning smell and immediately turned off the cooking gas.
(a)
What values were shown by Nitya’s brother?
ans.
intelligent, responsible
(b)
What are gaseous fuels? Give any two examples of gaseous fuels.
ans.
The fuels that exist in nature in the gaseous state besides being manufactured from solid and liquid fuels are known as gaseous fuels.
Some examples of gaseous fuels are natural gas, petroleum gas, coal gas and biogas.
(Ch 8: Fuel, Fire and Flame, pg 113)
7.
(a) What is the function of a nucleus?
(b) What is the function of genes?
(c) When are the chromosomes seen?
ans.
(a) Nucleus controls all the activities of the cell.
(b) Genes transfer trait or characteristic from parents to the offspring.
(c) Chromosomes are seen only when the cell divides.
(Ch 2: Cells- The building blocks of life, pg 20)
CB/VIII/1718 Practice Sheet - 2 page 3 of 5
8.
What is friction? What are the disadvantages of friction? (Write any two points.)
ans.
 The force which opposes the motion of a body while moving on a surface is called the force of friction.
 The disadvantages of friction are as follows:
 It causes wear and tear
 The heat produced due to friction gradually damages parts of a machine.
(Ch 13 Friction- A Necessary Evil, pg 184 and 188 )
9.
Differentiate between metal and non-metal based on the given criteria.
(a) Appearance
(b) Sonority
(c) Ductility
ans.
Criteria
Metal
Non-metal
Appearance
Metals are shiny in appearance. (lustre)
Non-metals have a dull appearance.
Sonority
Metals are said to be sonorous.
Non-metals are said to be non-sonorous.
Ductility
Metals are ductile.
Non-metals are not ductile.
(Ch6: The World of Elements, Pg- 75)
5 mark questions
10.
(a) What is the SI unit of an electric charge?
(b) What do you mean when we say that a body is electrically charged or electrified?
(c) State the law of conservation of charges.
(d) What is triboelectric series?
(e) Explain the process of discharging.
ans.
(a) Coulomb
(b) The substances which acquire the property of attraction when rubbed against another substance are said to be charged with electricity or have been electrified.
(c) Electric charges can neither be created nor destroyed but can only be transferred from one object to another.
(d) Different materials have different affinity for electrons. Such an ordering or placing of substances is known as a triboelectric series.
(e) When a charged object comes in contact with a body which is not charged, electric charges jump from the charged to the uncharged body till the charges on the two bodies are equalised. This process is called discharging.
(Ch 16: Natural Forces, pg223, 224 and 226 )
CB/VIII/1718 Practice Sheet - 2 page 4 of 5
11.
(a)
Explain the terms:
i. Amplitude
ii. Time Period
iii. Frequency
ans.
i. Amplitude of a vibration is the maximum displacement of the vibrating object on either side of its mean position.
ii. Time period of a vibration is defined as the time taken by the vibrating object for one complete vibration.
iii. The frequency of a vibration is defined as the total number of complete vibrations by the vibrating object in one second.
(b)
How are time period and frequency of a vibration measured? Write the units.
ans.
Time period is measured in seconds (s).
Frequency is measured in hertz (Hz).
(c)
Name any two characteristics of sound.
ans.
pitch, loudness and quality (or timbre).
(Ch 14: The Music of Sound Energy, pg 200)
12.
(a) What are communicable diseases?
(b) Name any three diseases caused due to bacteria in human beings and specify their mode of transmission.
(c) Name any two plant diseases.
ans.
(a) Diseases that are transmissible (as from person to person) by direct contact with an infected individual or the individual’s discharges or by indirect means (as by a vector) are called communicable diseases.
(b)
Disease
Mode of transmission
Tuberculosis
Air
Cholera
Water/Food
Typhoid
Water/Food
(c) Bacterial leaf spot, citrus canker are plant diseases.
(Ch 4: Life under a Microscope, pg 51- 52)
CB/VIII/1718 Practice Sheet - 2 page 5 of 5
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2 mark questions (Practical skill based questions)
13.
Trisha took two board pins A and B. Pin A has a sharp pointed tip and pin B has a flat blunt tip. She tried to press them on a soft board with equal force.
(a)
Which pin will easily pierce through the soft board?
ans.
Pin A
(b)
Write your conclusion with respect to area of contact and pressure.
ans.
Smaller the area of contact, larger will be the pressure exerted.
(Ch12: Forces in action, Pg- 172)
14.
Attempt the following questions with respect to the diagram of muscles shown below.
(a)
Identify the type of muscles.
ans.
A- skeletal muscle
B- cardiac muscle
(b)
Which of the two represents voluntary muscle?
ans.
A
(Ch 3: Tissues: Cells in Unison, pg 30-31)