Tag: chemistry

Questions Related to chemistry

To increase the percentage of oxygen in the atmosphere :

chemistry water and air and their importance importance of oxygen is air present everywhere around us? air as a natural resource

  1. plant more trees

  2. kill all living beings

  3. cut down trees

  4. protect animal life

Show answer
Correct Option: A
Explanation:
Planting more trees directly increases the oxygen amount by the process of photosynthesis which in turn increases the percentage of oxygen in the atmosphere.

Hence the option A is correct.

Plant consume ________ to make their own food.

chemistry water and air and their importance importance of oxygen is air present everywhere around us? air as a natural resource

  1. Oxygen

  2. Carbon dioxide

  3. Both A and B

  4. None of the above

Show answer
Correct Option: B
Explanation:

Plant consume carbon dioxide, water and other nutrients to make their own food.


The leaves contain a pigment called chlorophyll, which colours the leaves green. 


Chlorophyll can make food the plant can use from carbon dioxide, water, nutrients, and energy from sunlight. This process is called photosynthesis.


Hence the option B is correct.

Which of the following is incorrect regarding oxygen?

chemistry water and air and their importance importance of oxygen is air present everywhere around us? air as a natural resource

  1. Solid oxygen is blue.

  2. Oxygen gas is odorless.

  3. Oxygen is non-toxic.

  4. Liquid and solid oxygen are paramagnetic.

Show answer
Correct Option: C
Explanation:

Solid oxygen is a clear substance with a light sky-blue colour. Oxygen gas is a colourless gas without taste or odour. Oxygen toxicity is a condition that results from the harmful effects of breathing molecular oxygen $(O _2)$ at elevated partial pressures. This causes hyperoxia, an excess of oxygen in body tissues.

Something that is paramagnetic means that it is weakly attracted to the poles of a magnetic field but it itself does not retain any magnetic properties once it is beyond that magnetic field. Oxygen, no matter what its state, is paramagnetic.In solid and liquid oxygen, the magnetic effect is measurable but in a gas, the molecules of oxygen possess ample energy of motion to overcome the weak magnetic influence. 

Why was there no oxygen in the early atmosphere?

chemistry water and air and their importance importance of oxygen is air present everywhere around us? air as a natural resource

  1. No water

  2. No animals

  3. No vegetation

  4. No fire

Show answer
Correct Option: C
Explanation:

Oxygen is produced by plants by the process of photosynthesis,

earlier there were no plants and vegetation, thats why no oxygen in the early atmosphere. 

Which of the following plays a very important role in the oxygen cycle?

chemistry water and air and their importance importance of oxygen is air present everywhere around us? air as a natural resource

  1. Birds

  2. Animals

  3. Plants

  4. Soil

Show answer
Correct Option: C
Explanation:

Plants plays a very important role in the oxygen cycle as plants create the majority of oxygen we breathe through the process of photosynthesis. In this process plants use $CO _2,$ sunlight and water to create energy. In this process they also create oxygen which they release into the air.

Plants also consumes ________ for respiration.

chemistry water and air and their importance importance of oxygen is air present everywhere around us? air as a natural resource

  1. Carbon dioxide

  2. Oxygen

  3. Nitrogen

  4. Both A and B

Show answer
Correct Option: B
Explanation:

Plants also consume oxygen for respiration.


At night, when photosynthesis can’t take place, plants continue to consume oxygen but they don’t release any back into the atmosphere.


As the amount of oxygen consumes by the plants is very low during respiration so it doesn't effect the oxygen levels of the atmosphere.


Hence the correct option is B.

Heavy water violence is formed on combining deuterium with ___________ .

chemistry water and air and their importance importance of oxygen is air present everywhere around us? air as a natural resource

  1. heavy isotope of oxygen only

  2. oxygen

  3. ammonia

  4. nitrogen

Show answer
Correct Option: B
Explanation:

Heavy water violence is formed on combining deuterium with oxygen.

Which of the following changes are irreversible?

chemistry changes around us can all changes be reversed? substances and objects classification of changes

  1. Raw egg to boiled egg

  2. Woollen yarn to knitted sweater

  3. Bud to flower

  4. All of the above

Show answer
Correct Option: D
Explanation:

The following changes are irreversible.We cant covert product into reactant in these processes

1) Raw egg to boiled egg.
2) Woollen yarn to the knitted sweater.
3) Bud to flower.

Which of the following represents a reversible change?

chemistry changes around us can all changes be reversed? substances and objects classification of changes

  1. A metal rod on heating expands (its length increases).

  2. A metal rod on cooling contracts (its length decreases).

  3. Both of the above

  4. None of the above

Show answer
Correct Option: C
Explanation:

The following represents a reversible change. A metal rod on heating expands (its length increases). A metal rod on cooling contracts (its length decreases).

Small gaps are left between the metal rails on railway tracks in order to allow for :

chemistry changes around us can all changes be reversed? substances and objects classification of changes

  1. expansion of the metal rails on cold days

  2. contraction of the metal rails on hot days

  3. contraction of the metal rails on cold days

  4. expansion of the metal rails on hot days

Show answer
Correct Option: D
Explanation:
All metals expand when heated. If two railway tracks are laid together without any gap between them they will push against each other when they expand in the day time because of the heat of the sun, and when they cool down in the night they will contract and return to their original state pulling against each other. 
This constant pushing and pulling against one another when they heat and expand in the day time and cool down and contract in the night will result in the weakening of the joints between the two tracks and after a few days the two tracks may also break free from one another.
Such a situation will result in the derailment of the trains causing major accidents and loss of lives.

To prevent this, the railway engineers always leave a small gap between two rails to compensate for the expansion of the rails during the hot day time and contraction during cold nights.

Hence, the correct option is $\text{D}$