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Science - Class 7
ScienceClass 7

Science

Basic science concepts for Class 7

Previous Year Questions

Practice questions from Science Science

1

Which of the following is/are the example/examples of chemical change?

  1. Crystallization of sodium chloride
  2. Melting of ice
  3. Souring of milk

Select the correct answer using the code given below.

A. 1 and 2 only
B. 3 only(Correct Answer)
C. 1, 2 and 3
D. None

Crystallization of sodium chloride and melting of ice are physical changes as they involve a change of state. Souring of milk is a chemical change because it results in the formation of new substances.

Source: 7th NCERT: Science Chapter

2

Which of the following is/are the example/examples of chemical change?

  1. Crystallization of sodium chloride
  2. Melting of ice
  3. Souring of milk

Select the correct answer using the code given below.

A. 1 and 2 only
B. 3 only(Correct Answer)
C. 1, 2 and 3
D. None

Crystallization of sodium chloride and melting of ice are physical changes as they involve a change of state. Souring of milk is a chemical change because it results in the formation of new substances.

Source: 7th NCERT: Science Chapter

3

Which of the following statements is/are correct?

  1. Viruses lack enzymes necessary for the generation of energy
  2. Viruses can be cultured in any synthetic medium.
  3. Viruses are transmitted from one organism to another by biological vectors only

Select the correct answer using the codes given below.

A. 1 only(Correct Answer)
B. 2 and 3 only
C. 1 and 3 only
D. 1, 2 and 3

Option 1 is right because viruses do not have the chemical machinery needed to survive on their own.

Option 2 is wrong because they seek out host cells in which they can multiply. Viruses can't be grown on synthetic media (e.g. agar [a type of gelatin]) but they can be grown on cultures of bacteria. Bacteria reproduce and live like any other living organism would; they take in nutrients and reproduce using binary fission (like mitosis).

Viruses, on the other hand, are like little aliens. They really aren't living since they don't absorb nutrients or produce waste. Rather, they hook onto another cell (e.g. a bacterium) and inject the cell with its own viral genetic code. This code then causes the cell to produce multiple copies of the virus, essentially doing the reproduction for the virus at the cost of its own resources. The virus can't reproduce itself without another cell to build its copies. Therefore, we can't grow a virus on synthetic media.

Option 3 is also wrong because viruses enter the body from the environment or other individuals from soil to water to air via nose, mouth, or any breaks in the skin and seek a cell to infect.

Source Citation: NCERT: Class X Science

4

Which of the following statements are correct regarding the general difference between plant and animal cells?

  1. Plant cells have cellulose cell walls whilst animal cells do not.
  2. Plant cells do not have plasma membrane unlike animal cells which do.
  3. Mature plant cell has one large vacuole whilst animal cell has many small vacuoles.

Select the correct answer using the code given below:

A. 1 and 2 only
B. 2 and 3 only
C. 1 and 3 only(Correct Answer)
D. 1, 2 and 3

The most important difference between a plant cell and an animal cell is that the former has a cell wall. A cell wall gives mechanical support to a plant cell. Animal cells do not have cell walls.

Plants have both a cell wall that is made up of cell membrane (plasma membrane) and cellulose. The cell wall is a rigid membrane matrix found on the surface of all plant cells whose primary role is to protect the cell and its content. Hence statement 1 is correct and statement 2 is not correct.

Plant cells have a large central vacuole that can occupy up to 90% of the cell’s volume. Animal cells may have many small vacuoles, a lot smaller than the plant cell. Hence statement 3 is correct.

Source: NCERT

5

Consider the following pairs:

VitaminDeficiency Disease
Vitamin CScurvy
Vitamin DRickets
Vitamin ENight blindness

Which of the pairs given above is/are correctly matched?

A. 1 and 2 only(Correct Answer)
B. 3 only
C. 1, 2 and 3
D. None

Vitamin A causes Night Blindness.

Source: NCERT: Class 9 Science

Previous Year Questions

Test your knowledge with these practice questions

Question 1 of 50 / 5 answered
1

Which of the following is/are the example/examples of chemical change?

  1. Crystallization of sodium chloride
  2. Melting of ice
  3. Souring of milk

Select the correct answer using the code given below.

Year: 2014

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