7th Science (Semi) IMP Q&A 2nd term

 

7th Science (Semi) IMP Q&A 2nd term

Chapter 11to 20

 

Q.1. Fill in the blanks with the proper word.

(1) The substance that helps water to remove dirt from the surface of materials is called detergent .

(2) Fluoride is used in toothpaste to prevent tooth decay .

(3) Soap is a salt of fatty acid and sodium hydroxide.

(4) Synthetic detergents can be used in hard water as well.

(5) For construction purposes Portland cement is the most commonly used cement.

(6) The organelle called the plastid is present in plant cells only.

(7) Garbage is converted into fertilizers by micro-organisms.

(8) In the cell, photosynthesis is carried out with the help of chloroplasts .

(9) An electron microscope is necessary for the study of microbes/cell organelles .

(10) The process of digestion starts from the mouth .

(11) Eyelids have voluntary muscles.

(12) Production of blood cells is not a function of the muscular system.

(13) Muscles of the heart are cardiac muscles .

(14) Pushing forward the food that has been chewed is the function of the oesophagus .

(15) When the beams from the headlights of a car fall on an object in the night, the shadows called umbra and penumbra can be seen.

(16) During a lunar eclipse the shadow of the earth falls on the moon .

(17) During a solar eclipse the shadow of the moon falls on the earth .

(18) Various shades of colour are seen in the sky at sunrise and sunset due to scattering of light .

(19) Sound is generated by the rhythmic vibrations of any object.

(20) The frequency of sound is measured in Hertz .

(21) If amplitude of sound is decreased, its loudness also decreases.

(22) A medium is necessary for propagation of sound.

(23) The alloys called nipermag and alnico are used for making industrial magnets.

(24) A magnetic field can pass through cardboard and water .

(25) The intensity of a magnetic field is indicated by the lines of force .

(26) The real test of a magnet is repulsion .

(27) When seen from a great distance, the sky seems to be touching the ground along a circle. This circle is called the horizon .

(28) The ecliptic is used while defining the zodiac signs.

(29) Classified according to seasons, one season will have nine nakshatras.

(30) The rising of the sun in the east and its setting in the west is the apparent motion of the sun .

Q.2. Find a match for me.

Group ‘A’                                   Group ‘B’

1. Cardiac muscles      (a) always function muscles in pairs.

2. Are brought about by muscles          (b) we never feel tired.

3. Pepsin                     (c) uncontrolled and painful contraction of muscles.

4. Cramps                   (d) chewing movements of jaws.

5. Skeletal muscles    (e) enzyme of the gastric juice.

6. Stainless steel         (f) Non-metal

7. Silver                      (g) Compound

8. Bhajani mixture      (h) Mixture for milling

9. Salt                         (i) Element

10. Coal                      (j) Alloy

11. Hydrogen              (k) Metal

12. Flute                     (l) Frequency less than 20 Hz

13. Frequency             (m) Frequency more than 20000 Hz

14. Sound level          (n) Vibrations in the air

15. Ultrasonic sound   (o) Measured in Hz

16. Infrasonic sound   (p) Decibel

17. Compass               (q) The highest magnetic force

18. Door of a cupboard(r) Like poles

19. Repulsion               (s) A magnet

20. Magnetic pole          (t) A magnetic needle

Answers:-        

1. Cardiac - (b) we never feel tired.

2. Are brought about by muscles - (d) chewing movements of jaws.

3. Pepsin - (e) enzyme of the gastric juice.

4. Cramps - (c) uncontrolled and painful contraction of muscles.

5. Skeletal - (a) always function muscles in pairs.

6. Stainless steel - (j) Alloy

7. Silver - (k) Metal

8. Bhajani mixture - (h) Mixture for milling

9. Salt - (g) Compound

10. Coal - (i) Element

11. Hydrogen - (f) Non-metal

12. Flute - (n) Vibrations in the air

13. Frequency  - (o) Measured in Hz

14. Sound level - (p) Decibel

15. Ultrasonic sound - (m) Frequency more than 20000 Hz    

16. Infrasonic sound - (l) Frequency less than 20 Hz     

17. Compass  - (t) A magnetic needle

18. Door of a cupboard - (s) A magnet

19. Repulsion  - (r) Like poles

20. Magnetic pole - (q) The highest magnetic force

Q.3. Who is telling lie  ?

1. Tongue - My taste-buds can tell only a sweet taste.

Answer : Tongue is lying. It can sense all the different tastes.

2. Liver - I am the largest gland in the body.

Answer : Liver is telling truth.

3. Large intestine - I am 7.5 meter long.

Answer : Large intestine is telling lie. Its length is 1.5 meter long.

4. Appendix - Digestion is impossible without me.

Answer : Appendix is lying. It does not perform any function in human body.

5. Lung - I play an important role in excretion.

Answer : Lung is telling partial lie. It can perform function of excretion. But not as important role as performed by kidney.

 

Q.4. Under which different types can the following changes be classified ?

(a) Conversion of milk into yoghurt.

 - Chemical, irreversible, slow.

(b) Bursting of a cracker.

- Chemical, irreversible, fast.

(c) Occurrence of an earthquake.

- Physical, chemical, irreversible, natural.

(d) Revolution of the earth around the sun.

- Periodic, slow, natural.

(e) Stretching of a spring.

- Physical, reversible.

 

Q.5. Write the names of elements from the following symbols :

Symbol	Element	Symbol	Element
Zn	Zinc	Cu	Copper(cuprus)
Cd	Cadmium	Fe	Iron(Ferrum)
Xe	Xenon	Si	Silicon
Br	Bromine	Ir,	Iridium
Ti	Titanium	Pt	Platinum

 

Q.6. What are the molecular formulae of the following compounds ?

 

Compound	Molecular formula
Hydrochloric acid	HCL
sulphuric acid	H2SO4
sodium chloride	NaCl
glucose	C6H12O6
methane	CH4

Q. 7. Answer the following questions: 

(1) What is a 'cell'? 

Ans. The structural and functional unit of the body is called a cell. 

(2) What are micro-organisms? 

Ans. The living organisms on the earth which are in every environment but can be seen only under compound microscope are called micro-organisms. 

(3) How many types of muscles are there? Which are those types? 

Ans. The muscles are of three main types, viz. (1) Skeletal or voluntary muscles (2) Cardiac muscles (3) Smooth or involuntary muscles. 

(4) What causes the problem of acidity? What is its effect on the body? 

Ans. Acid is produced by stomach. It is mild 0.5 % HCl. If excess of acid is produced it causes headache, heart burns, vomiting or skin rashes. 

(5) Which elements are present in air?

Ans. Oxygen, nitrogen, hydrogen, argon, crypton, xenon, etc. are the elements present in the air. 

(6) What are the ingredients of cement? 

Ans. The ingredients of simple cement are silica (sand), alumina (aluminium oxide), lime, iron oxide and magnesia (magnesium oxide). In Portland cement, there is 60% lime (calcium oxide), 25% silica (silicon dioxide), 5% alumina and remaining iron oxide and gypsum (calcium sulphate).

(7) Make a list of the components we obtain from mineral oil. 

Ans. Crude mineral oil is a mixture of many hydrocarbon compounds. Components obtained from mineral oil : Aviation petrol, gasoline, diesel, kerosene, naptha, lubricant oils and tar.

(8) Why is a penumbra not obtained from a point source? 

Ans. Scattering of light emerging from a point source does not take place. Thus, only dark shadow of the object placed in front of the point source is obtained.

(9) What are the types of sound based on frequency of sound

Ans. Following are the types of sound on the basis of frequency of sound: 

(1) Infrasonic sound: A sound of frequency less than 20 Hz. 

(2) Audible sound: A sound of frequency between 20 Hz to 20000 Hz. (3) Ultrasonic sound: A sound of frequency higher than 20000 Hz.

(10) What is a constellation? 

Ans. A group of stars occupying a small portion of celestial sphere is called a constellation. Some of these stars appear to form certain animal or human figures and objects. These constellations are known by the brightest star present in it.

(11) Why pole star is important in sky observation? 

Ans. Since Pole star occupies a position on the earth's axis passing through the north pole. Therefore, it always points the north in a sky map. The position of Pole Star can be also indicated by constellation of Saptarshi i.e. The Great Bear on one side and Sharmishtha i.e. Cassiopeia on the other side. 

Q. 8. Give scientific reasons:

(1) Food becomes acidic in the stomach. 

Ans. The wall of the stomach has gastric glands that produce mild hydrochloric acid. Due to this the food becomes acidic in the stomach. 

(2) A refrigerator is used in almost every home. 

Ans. The harmful microbes do not grow in cold temperatures. they grow only in the temperature range of 15° C to 35° C. Refrigerator has very low temperatures. Food can be stored there without spoiling. Therefore, to store perishable food items refrigerators have become essential in every home. 

(3) Buttermilk is churned to get butter. 

Ans. Churning is one of the method of separation. The particles of butter are all spread out in the buttermilk. By stirring they aggregate due to centrifugal force and form one solid lump. To separate the butter, the buttermilk is therefore churned.

(4) Tobacco masheri should not be used for cleaning teeth. 

Ans. Tobacco is a harmful substance for the health. It can cause addiction and cancer. Masheri made up of tobacco can cause harmful effects on teeth and gums. Therefore, tobaco masheri should not be used for cleaning teeth.

(5) Space beyond the earth's atmosphere appears dark. 

Ans. There is a vacuum beyond earth's atmosphere, due to which there is no medium for scattering of sunlight. As a result, space appears dark.

(6) We should not observe the solar eclipse with naked eyes. 

Ans. The earth receives the harmful ultra-violet rays from the sun. During a solar eclipse, even if brightness of the sun is less, the ultra-violet rays reach the earth. If the solar eclipse is seen/watched with naked eyes, the ultra-violet rays directly enter our eyes and damage vision. Hence, the solar eclipse should not be observed with naked eyes.

(7) The sky appears blue during the day. 

Ans. The molecules of gases like nitrogen, oxygen present in the atmosphere, scatter the sunlight. At this time, the blue colour in the sunlight scatter the most. Hence, the sky appears blue during the day.  

8) If you were both on the moon, your friend will not be able to hear you call.

Ans: : Transmission of sound requires a medium. Since the moon does not have an atmosphere like the earth, due to the lack of medium, the sound we speak on the moon cannot be transmitted from one place to another. That's why if you call your friend will not be able to hear.

Q.9. Complete the flow chart.