Class VIII/AE-Science-2017

Ministry of Education

DZONGKHAG COMMON EXAMINATION-2017

SARPANG

VIII Science                                                                                             Writing Time: 2hrs

 Subject: Science                                                                                      Full Marks: 100

SECTION A (Compulsory): 55 Marks

Question 1

Direction:Each question is followed by four possible answers. Choose the correct answer and write it down in your answer sheet.

1.     Sonam experienced electric shock and jumped away. Which body tissues are most involved in his reaction?

A.  Connective tissue and muscular tissue

B.  Epithelial tissue and muscular tissue

C.  Epithelial tissue and nervous tissue

D.  Nervous tissue and muscular tissue

2.     The main gases involved in gaseous exchange in our lungs are:

A.  Carbon dioxide and oxygen

B.      Carbon dioxide and nitrogen

C.      Nitrogen and oxygen

D.      Oxygen and carbon monoxide

3.     Many cells combine together to form a tissue. A tissue responsible for connecting muscle to bone in our body is

A.      Cartilage

B.      Ligament

C.      Tendon

D.      Nerve

4.     All of the following are the causes of polluted air EXCEPT?

A.    Dizziness

B.     Chest pain

C.     Obesity

D.    Lung cancer

5.     “These cells contain hair-like fine projections that help to receive the stimuli of the odour of the substance”. The above statement best describes

A.      Red blood cells

B.      White blood cells

C.      Animal cells

D.      Olfactory cells

6.     Organic farming includes crop rotation, mixed cropping, mulching etc. The suitable outcome of mulching is?

A.    Destroys harmful pest

B.    Maintains moistures and improve soil condition

C.    Increase the life span of the crop

D.    Decrease crop yield

7.     Many educator encourages organic products because

A.    They are rich in minerals

B.    They do not contain harmful chemicals

C.    They are freely available

D.    They are cost effective 

8.     The method of breeding new plants by choosing the pollen from one variety of plant and placing it onto the stigma of another variety of plant is called

A.      Active selection

B.      Breeding selection

C.      Hybridization

D.      Selective breeding

9.     Sustainable development aims at

A.              Accumulation of resources

B.               Increased resources consumption

C.               Meeting the needs of the present and future

D.              Socioeconomic development

10.  A chemical compound is a pure substance formed by the chemical combination of two or more atoms of different element in a fixed proportion. Which one of the following is a compound?

A.    CO₃^2-

B.    NaCl

C.    O₂

D.    HSO^4-

11.  The atomic number of sodium is 11. The maximum possible number of electron in M-shell is

A.    11

B.    8

C.    2

D.    1

12.  The chemical formulae of calcium nitrate is

A.      Ca(NO₃)₂

B.      CaNO₃

C.      Ca₂NO₃

D.      CaNO₂

13.  Iron (Fe) reacts with oxygen (O₂) to form iron (III) oxide (Fe₂O₃). The properties of Fe₂O₃ are most likely to be

A.      Different from iron and oxygen

B.      Similar to both iron and oxygen

C.      Similar only to oxygen

D.      Similar only to iron

14.  Which one of the following is a decomposition reaction?

A.   C + O₂------à CO₂

B.    Na₂CO₃----àNa₂O + CO₂

C.    Zn + 2HCl---à ZnCl₂ + H₂

D.    2Mg + O₂ -----à 2MgO

15.  The best technique to separate petrol from crude oil is

A.     Chromatography

B.      Fractional distillation

C.     Filtration

D.     Simple distillation

16.  Dawa took a metal in atest tube and added an acid. Effervescence was observed. Dawa collected the gas and tested with a light splint. The gas produced a pop sound. Therefore, the gas produced by the reaction is

A.      Carbon dioxide

B.      Hydrogen

C.      Oxygen

D.      Water vapour

17.  If equal quantities of hydrochloric acid and sodium hydroxide solution are mixed, what will be the nature of the final solution?

A.      Acidic

B.      Alkaline

C.      Basic

D.      Neutral

18.  The value of ‘g’ near the pole will be

A.      Less than 9.8 ms^-2

B.      More than 9.8 ms^-2

C.      Equal to 9.8 ms^-2

D.      Equal to 1.62 ms^-2

19.  Yangchen rides a bicycle on 200 m circular track three times. The displacement of Yangchen when she completes two rounds will be:

A.      600 m

B.      200 m

C.      0 m

D.      400 m

20.  The fastest mode of transfer of heat is:

A.      Conduction

B.      Convection

C.      Radiation

D.      Same in all the three modes

21.  A device that breaks a circuit during the flow of excess current and can be reset is called

A.      Earthing

B.      Fuse

C.      Miniature circuit breaker

D.      Switch

22.  Which statement is TRUE about the direct current?

A.      It is unidirectional

B.      It has varying direction

C.      It is produced in hydropower station

D.      It is supplied by main electricity

23.  Which one of the following is a heating appliance?

A.      Bulb

B.      Computer

C.      Water boiler

D.      Washing machine

24.  The speed of light __________ when it passes from denser medium to rarer medium.

A.      Decrease

B.      Increase

C.      Remain same

D.      None of the above

25.  If an object reflects blue light and absorbs all the other colours, what colour does the object appear to be?

A.      Black

B.      Blue

C.      Green

D.      White

Question 2

Fill in the blanks.                                                                                [1x10=10]

1.     The resources which are replaced naturally are called..................

2.     A base with non metallic ion ………………..

3.     Ovulation takes place in ……………..of human reproductive system.

4.     Establishment of forest in barren land........................

5.     Petroleum products are separated by ………………....

6.     ............................. is the smallest bone in human body.

7.     The factor that determines the flow of heat from one body to another is ………………………

8.     The competition between individuals of two different species for same resources in an ecosystem is called…………………

9.     The protection, preservation and careful management of natural resources is called ………………………..

10.  ……………… are atoms of the same element having the same atomic number but different mass number.

Question 3

Direction: Write TRUE or FALSE against the given statements. Correct the False statement.                                                                                    [1x10=10 marks]

1.     All bases are alkalis.

2.     Steel is an example of compound.

3.     With increase in temperature the solubility of a substance decreases.

4.     Leaching of chemical fertilizers lead to eutrophication.

5.     Protoplasm includes cytoplasm, cell organelles and vacuoles.

6.     The study of tissues is called histology.

7.     A heart is an organ system.

8.     Endothermic reaction requires heat.

9.     The skull has no joint.

10.  A bond is an attractive force which binds the atoms in a molecule.

Question 4

Direction: match the items of column I with correct answers of column II. [1x10= 10 marks]

Column A	Column B
1.     Neuron	a. root nodules
2.     Oesophagus	b. muddy water
3.     Beans	c. exothermic reaction
4.     Solubility of cerium sulphate	d. nutrition
5.     Filtration	e. peristalsis
6.     Neutralization	f. vector quantity
7.     Velocity	g. directed towards the centre
8.     Placenta	h. acid base reaction
9.     Refraction	i. connects to throat
10. Centripetal force	j. carries impulse
	k. bending of light

SECTION B: 45 Marks

Direction: There are FIVE questions in this section. Answer ALL the questions.

Question 5                                                                                  [9 Marks]

a)     The two types of farming are organic farming and inorganic farming. Which one will you prefer? Support your answer with reasons. [2]

b)      Look at the figure below and answer the following questions. [1+1+2+2+1=7]

                    i.       The atomic number of the element in the above figure is……….

                  ii.       The number of the electron is………

                iii.       Calculate the mass number of the element.

                 iv.       Show the arrangement of electrons in the atomic structure given in the above figure.

                   v.       Identify the element represented by above figure

Question 6                                                                        [9 Marks]

a)     Calculate the potential difference across a 10 Ω resistor carrying a current 2.5 A.      [2]

b)     Draw a ray diagram to show the refraction through prism. Label the following in the diagram.    [4]

                            i.           incident ray

                          ii.          refracted ray

                        iii.           emergent ray

                         iv.          angle of deviation

c)     Fill in the blanks numbered I to IV in following table. [2]

Name of cell organelle	Function
Cell wall	i.                 …………………………..
ii.               ……………………..	Destroy foreign and injured substance
Chloroplast	iii.             ……………………………
iv.             ……………………………..	Stores food ,minerals and other substance

d)     Name an acid present in lemon. [1]

Question 7                                                                                  [9 Marks]

a)     Excessive use of chemical fertilizers in farming affects our environment. Explain. [2]

b)     Given below is overall chemical reaction of certain process.

Glucose                                 lactic acid + 2ATP

                            i.          Name the process [1]

                          ii.          Is this reaction applicable to animals or plant? Why? [2]

c)     Draw the ray diagrams for the formation of image of an object when the object is between F1 and optical centre O. Write the characteristics of the image. [4]

Question 8                                                                                    [9 marks]

a)     As a concern citizen of Bhutan, what measures will you take to minimize acid rain? [3]

b)     Use your knowledge of mixture and compound to differentiate between sodium chloride and sodium chloride solution. [2]

c)     A bull pulls a plough with a constant force of 2000N along a field through a distance of 10 m in 50s. What is the power of bull? [2]

d)     A miniaturecircuit breaker (MCB) isbetter than a fuse. Give reasons. [2]

Question 9                                                                                  [9 marks]

a)     Give reasons for the following:  [3]

                                        i.        Aeroplanes, missiles and space ships are pointed.

                                      ii.        The foundation of a dzong is broad.

                                    iii.        Chemical reaction is a chemical change.

b)     Give one word answer for the following statement. [2]

                                        i.        Mixture of solute and solvent

                                      ii.        Ability of solute to dissolve

c)     A hybrid is produced as a result of breeding a donkey and a horse.

                                        i.        Name the hybrid. [1]

                                      ii.        What will be the characteristics of the hybrid? [1]

d)     “The heavenly bodies that are seen bright are big in size”. Do you agree or disagree? Justify your answer. [2]