NCERT Science Major Test Model Paper Class 7 2020 Questions and Answers Part 4

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22. (a) What is displacement reaction? Explain with an example.

(b) What is crystallization?

(c) Give an example of combination reaction and decomposition reaction each.

Ans:

(a) When one element displaces another element from a compound and takes its place, the reaction is called a displacement reaction.

Displacement:

Magnesium displaces hydrogen from hydrochloric acid (hydrogen chloride) and combines with the chloride ion to form magnesium chloride.

Sodium displaces hydrogen from water and forms sodium hydroxide.

(b) The process of cooling a hot, concentrated solution of a substance to obtain crystals is called crystallization. Crystallization is a process that separates a pure solid in the form of its crystals from a solution.

(c) Combination

Decomposition

Section-C: Biology

23. Many animals living in the polar region possess which of these features?

(1) Strong tails

(2) Long and large beak

(3) Presence of blubber

(4) Long ears

Ans: (3) Many animals living in polar region possess blubber under their skin.

24. _______ animals excrete ammonia in gaseous form.

(1) Aerial

(2) Land

(3) Aquatic

(4) Desert

Ans: (3) Aquatic animals excrete ammonia in gaseous form.

25. Agencies for cross pollination are

(1) Insect

(2) Air

(3) Water

(4) All of the above

Ans: (4) Insects, air and water are the agencies of cross pollination.

26. In following food chain total number of carnivores are

(1) One

(2) Two

(3) Three

(4) Four

Ans: (3) There are 3 carnivores in the given food chain i.e. frog, snake and eagle.

27. Statement-I: The green parts of the leaf can perform photosynthesis.

Statement-II: Chlorophyll present in green parts of leaf can capture the energy of sunlight required for photosynthesis.

(1) Both statements I and II are true and the statement II is the correct explanation of statement I.

(2) Both statement I and II are true but statement II is not the correct explanation of statement I.

(3) Statement I is true, but statement II is false.

(4) Both statement I and II are false.

Ans:

(1) The green parts of leaf perform photosynthesis because chlorophyll, the green pigment present in green parts of leaf capture energy of sunlight required for photosynthesis.

28. Name the vascular tissue that

(i) Transports water and minerals in the plant.

(ii) Transports food in plant.

Ans:

(i) Xylem

(ii) Phloem

29. Give one example of

(i) Insectivorous plant

(ii) Symbiosis

Ans:

(i) Nepenthes / Pitcher plant

(ii) Mycorrhiza, lichen (any 1)

30. Give two examples each of unisexual and bisexual flowers.

Ans:

Unisexual - papaya, corn, cucumber (any 2)

Bisexual - Rose, mustard, petunia (any 2)

31. (i) Draw a well labelled diagram of human excretory system.

(ii) List any two functions of kidney.

Ans:

(i)

human excretory system

Human Excretory System

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(ii) Functions of kidneys (any two)

  • Excretion of waste products.

  • Removal of toxic chemicals.

  • Maintains water/osmotic balance in the blood (Osmoregulation).

  • Elimination of excess vitamins, drugs etc.