Tag: chemistry

Quizzes (490) Questions (9892)

Questions Related to chemistry

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

To increase the percentage of oxygen in the atmosphere :

  1. plant more trees

  2. kill all living beings

  3. cut down trees

  4. protect animal life
Reveal answer Fill a bubble to check yourself
A Correct answer
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.
Multiple choice chemistry water and air and their importance importance of oxygen is air present everywhere around us? air as a natural resource

Plant consume ________ to make their own food.

  1. Oxygen

  2. Carbon dioxide

  3. Both A and B

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

Which of the following is incorrect regarding oxygen?

  1. Solid oxygen is blue.

  2. Oxygen gas is odorless.

  3. Oxygen is non-toxic.

  4. Liquid and solid oxygen are paramagnetic.
Reveal answer Fill a bubble to check yourself
C Correct answer
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. 

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

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

  1. Birds

  2. Animals

  3. Plants

  4. Soil
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

Plants also consumes ________ for respiration.

  1. Carbon dioxide

  2. Oxygen

  3. Nitrogen

  4. Both A and B
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

Which of the following changes are irreversible?

  1. Raw egg to boiled egg

  2. Woollen yarn to knitted sweater

  3. Bud to flower

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

Which of the following represents a reversible change?

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
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).

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

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

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
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 $\text{D}$