Tag: materials

Questions Related to materials

Which one of the following is a correct statement?
1. Ice provides more cooling effect than water at $273\ K$.
2. Evaporation of a liquid causes cooling.
3. Increase of pressure lowers the separation between the particles of matter.

chemistry materials liquid crystals liquid state the liquid state

  1. $1$ and $2$

  2. $1$ and $3$

  3. $2$ and $3$

  4. $1, 2$ and $3$

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Correct Option: D
Explanation:

Ice provides more cooling effect than water at 273 K because of latent heat of fusion. Evaporation of a liquid causes cooling as the surface molecules take away heat to escape out. Increase of pressure lowers the separation between the particles of matter and brings them closer leading to change of state from gas to liquid and to solid.

The best evidence for the existence and movement of particles in liquids was provided by ______________.

chemistry materials liquid crystals liquid state the liquid state

  1. John Dalton

  2. Thomas Edison

  3. J.J. Thomson

  4. Robert Brown

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Correct Option: D
Explanation:

Robert brown observed a weak solution of milk and later pollen grains in suspension with a high-powered microscope, and saw that the particles of milk and the pollen grains showed a violent and random motion. This motion was named as Browninan motion.

What is the shape of the meniscus observed when water and mercury are taken in two different capillary tubes?

chemistry materials liquid crystals liquid state the liquid state

  1. Concave and convex

  2. Convex and concave

  3. Both concave

  4. Both conves

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Correct Option: A
Explanation:

The shape of the meniscus observed when water and mercury are taken in two different capillary tubes is concave and convex respectively.

The amount of energy required to change $1\ kg$ of a solid into liquid at atmospheric pressure at its melting point is known as _______________.

chemistry materials liquid crystals liquid state the liquid state

  1. latent heat of fusion

  2. latent heat of boiling

  3. latent heat of freezing

  4. melting energy

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Correct Option: A
Explanation:
The amount of energy required to change $1\ kg$ of a solid into liquid at atmospheric pressure at its melting point is known as latent heat of fusion.

Hence option A is correct.

These two compounds are in the liquid phase at $293\ K$ :

chemistry materials liquid crystals liquid state the liquid state

  1. $Br _{2}$ and $Hg$

  2. $Cl _{2}$ and $F _{2}$

  3. $NH _{4}^{+}$ and $H _{3}O^{+}$

  4. $Fe$ and $Co$

  5. Diamond and graphite

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Correct Option: A
Explanation:

$Br _2$ and $Hg$ are in the liquid phase at $293 :K$.
$Cl _2$ and $F _2$ are gases.
$NH _4^+$ and $H _3O^+$ exist in aqueous solution.
$Fe$ and $Co$ are solids
Diamond and graphite are also solids.

An experiment is conducted where droplets of liquid are placed on the surface of a penny. Which of the following substances would you expect to the able to place the maximum number of drops of on the surface of the penny?

chemistry materials liquid crystals liquid state the liquid state

  1. $HF$

  2. $H _{2}O$

  3. $CH _{3}CH _{2}CHO$

  4. $CCl _{4}$

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Correct Option: A
Explanation:

Fluorine is most electronegative element so it forms stronger hydrogen bond which is the reason of stronger surface tension.So HF drops place maximum on the penny.

What happens to the rate of evaporation of water, if the atmospheric pressure is decreased during the extraction of colored components?

chemistry materials liquid crystals liquid state the liquid state

  1. Increases

  2. Decreases

  3. Do not change

  4. None

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Correct Option: A
Explanation:

The rate of evaporation of water increases, if the atmospheric pressure is decreased during the extraction of colored components because atmospheric pressure is inversely proportional to evaporation. 

What happens to the rate of evaporation of water, if the atmospheric pressure is increased during the extraction of the colored component from liquid? 

chemistry materials liquid crystals liquid state the liquid state

  1. Increases

  2. Decreases

  3. Do not change

  4. None

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Correct Option: B
Explanation:

Evaporation is a surface phenomenon in which surface molecules of solution moves to the atmosphere.If atmospheric pressure is increased then due to external pressure molecules on the surface will not move to the atmosphere so if atmospheric pressure increases, a rate of evaporation decreases.

The volume of gas is reduced to half from its original volume. The specific heat will be :

chemistry materials liquid crystals liquid state the liquid state

  1. reduce to half

  2. be doubled

  3. remain constant

  4. increase four times

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Correct Option: C

4n + 1 series is known by which name ?

chemistry materials liquid crystals liquid state the liquid state

  1. Actinium

  2. Neprunium

  3. Thorium

  4. Uranium

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Correct Option: B