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Science (Class VII)

Description: CBSE Class VII Test
Number of Questions: 10
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Tags: CBSE Class VII Test Respiration and its Types Obtaining and Processing of Wool Processing of Fibres into Wool and the Human Disease Associated with the Process Light Exchange of Gases in Humans Electric Current and its Effects Properties of Acids and Bases Physical and Chemical Changes Breathing in Other Animals and Plants
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People who are engaged in separating different types of wool often suffer from sorter's disease. Which bacteria is responsible for it?

  1. Neisseria bacteria

  2. Streptococcus bacteria

  3. Anthrax bacteria

  4. None of these

Show answer
Correct Option: C
Explanation:

A pulmonary form of anthrax that results from the inhalation of spores of the bacterium. Bacillus anthracis in the wool of some of the infected sheep.  

What do you understand by virtual image?

  1. An image which can be obtained on the screen.

  2. An image which cannot be obtained on the screen.

  3. An image which is inverted and magnified.

  4. None of these

Show answer
Correct Option: B
Explanation:

The light  rays meet  at a focal point behind the mirror. Hence, we cannot obtain an image on the screen.

Why does one get muscle cramps after excessive running or exercising?

  1. Because the muscle cells respire aerobically.

  2. Because of anaerobic respiration which takes place in the muscles.

  3. Because we breath more hard to fulfill the supply of oxygen.

  4. None of these

Show answer
Correct Option: B
Explanation:

Yes, anaerobic respiration takes place in our muscles to fulfill the supply of oxygen. Lactic acid is released resulting in its accumulation which causes cramps. Hot water bath/massage helps in relieving pain.

Why do we use tungsten to make the filament of a bulb?

  1. It has the lowest thermal expasion coefficient.

  2. It has high meting point.

  3. Both 1 and 2 are correct.

  4. None of these

Show answer
Correct Option: C
Explanation:

It glows because it doesn't melt at low temperature. Both these properties of tungsten metal makes it perfect to be used as filament of a bulb.

In yeast, the anaerobic respiration also called as alcoholic fermentation, is the basis of two major processes, ________ and _________.

  1. brewing and baking

  2. brewing and bio-diesel production

  3. baking and bio-diesel production.

  4. none of these

Show answer
Correct Option: A
Explanation:

Fermentation process in bread dough depends on the breakdown of the starches in flour, producing carbon dioxide which makes bubbles in the dough. In brewing, alcoholic fermentation is the conversion of sugar into carbon dioxide gas (CO2) and ethyl alcohol.

When blue vitriol solution reacts with a piece of iron, a new substance gets deposited on the piece of iron. What is the colour of the deposited substance?

  1. Green

  2. Blue

  3. Brown

  4. None of these

Show answer
Correct Option: C
Explanation:

The colour of the substance deposited is copper. Hence, this answer is correct.

We all know about acid rain. Which acid makes the rain acidic and is very harmful?

  1. Carbonic acid

  2. Nitric acid

  3. Suphuric acid

  4. All of these

Show answer
Correct Option: D
Explanation:

All of these. In the atmosphere, carbon di-oxide partially reacts with water to form carbonic acid (pumped in the atmosphere  mainly by burning of fossil fuel from volcanoes etc.) In the atmosphere, nitrogen oxide forms a weak solution of nitric acid (pumped in the atmosphere as a secondary pollutant.) In the atmoshere, sulphur di-oxide forms sulphuric acid. This is also called as a secondary pollutant. Answer is Option-5 All of these. Carbon -di -oxide in the atmosphere partially reacts with water to form carbonic acid( pumped in the atmosphere  mainly by burning of fossil fuel, from volcanoes etc. ) Nitrogen oxide in the atmosphere forms a weak solution of nitric acid ( pumped in the atmosphere as a secondary pollutant.) Sulphur -di -oxide in the atmoshere forms sulphuric acid ( this again as a secondary pollutant.)

Where does the exchange of gases during respiration in a cockroach takes place (taking in of oxygen and giving out carbon dioxide)?

  1. Lungs

  2. Trachea

  3. Spiracles

  4. None of these

Show answer
Correct Option: B
Explanation:

Trachea is a network of tubes present in insects where the exchange of gases takes place. This is the correct answer.

Why is horse dung mixed in black soil and heated to make items like surahi, mataka etc.?

  1. Burnt horse dung helps open pores in the soil.

  2. To give the item strength.

  3. It helps in retaining the shape easily.

  4. None of these

Show answer
Correct Option: A
Explanation:

It helps open pores so that water percolates out, evaporates and cools the water inside.

Clocks used for scientific research can measure the smallest time interval as small as

  1. one micro second

  2. one nano second

  3. one hundredth

  4. None of these

Show answer
Correct Option: B
Explanation:

It is the smallest time interval measured by clocks used for scientific research. A nano second is one billionth of a second.

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