Tag: changes and their classification

Questions Related to changes and their classification

Boiling water is a _____ change because _____.

chemistry change around us physical changes changes and their classification physical changes

  1. Physical, the gaseous water produced is chemically identical to the liquid water the process began with

  2. Physical, the water was disappeared

  3. Chemical, heat was required for the change

  4. Chemical, the process produced a gas

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Correct Option: A
Explanation:

Boiling water is a physical change because the gaseous water produced is chemically identical to the liquid water i.e both of them have the same molecular structure of the water.

According to the CRC's  the melting point of cadmium bromide is $868^{\circ}C$. Which of the following equations best describes what occurs when cadmium is heated to $868^{\circ}C$?

chemistry change around us physical changes changes and their classification physical changes

  1. $CdBr(s)\rightarrow CdBr(l)$

  2. $CdBr _{2}(s)\rightarrow CdBr _{2}(l)$

  3. $CdBr _{2}(s)\rightarrow Cd(s) + Br _{2}(g)$

  4. $CdBr _{2}(s)\rightarrow Cd^{2+}(aq) + 2Br^{-}(aq)$

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Correct Option: A

What kind of changes is undergone when an electric bulb glows?

chemistry change around us physical changes changes and their classification physical changes

  1. A physical change

  2. A chemical change

  3. Both a physical and a chemical change

  4. A permanent change

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Correct Option: A
Explanation:

When an electric bulb glows a physical change is observed. As the light produced by the electric bulb is due to the heating effect of the conductor. Even though there is an occurrence of temperature change since no new substances are produced it is considered to be a physical change.

Your lab partner mixed two colorless solutions in the test tube. He sees no observable changes in the resulting mixture and is unable to detect any change in temperature. Based on these observations, what type of reaction has taken place?

chemistry change around us physical changes changes and their classification physical changes

  1. A physical reaction

  2. A chemical reaction

  3. An exothermic reaction

  4. An endothermic Reaction

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Correct Option: A
Explanation:

When two solutions are mixed and no observable changes like evolution of gas or precipitate formation takes place then the reaction is reversible and the reaction is a physical reaction.

Ans :- A

The melting point of cadmium bromide is $568^{\circ}C$. Which of the following equations best describes what occurs when cadmium bromide is heated to $568^{\circ}C$?

chemistry change around us physical changes changes and their classification physical changes

  1. $CdBr(s)\rightarrow CdBr(l)$

  2. $CdBr _{2}(s)\rightarrow CdBr _{2}(l)$

  3. $CdBr _{2}(s)\rightarrow Cd(s) + Br _{2}(g)$

  4. $CdBr _{2}(s) \rightarrow Cd^{2+} (aq) + 2Br^{-}(aq)$

Show answer
Correct Option: B
Explanation:

Melting point is defined as the temperature at which solid is converted to liquid.

Given, Melting point of $Cd{ Br } _{ 2 }={ 568 }^{ 0 }C$

So, At ${ 568 }^{ 0 }C$

${ CdBr } _{ 2 }\left( solid \right) \longrightarrow { CdBr } _{ 2 }\left( liquid \right) $
Ans :- A

Adam traveled from his home in New York down to Florida for summer vacation. So you say that Adam experienced both a change in temperature and a change of state! When we study states of matter in chemistry, it is important to focus on atoms (not Adam).
Which of the following BEST describes the differences between atoms of solid sodium and atoms of liquid sodium?

chemistry change around us physical changes changes and their classification physical changes

  1. Atoms of solid sodium have smaller atomic radii than atoms of liquid sodium.

  2. Atoms of solid sodium are more chemically reactive than atoms of liquid sodium.

  3. Atoms of liquid sodium move around more freely than atoms of solid sodium.

  4. Atoms of liquid sodium experience stronger attractive forces than atoms of solid sodium.

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Correct Option: A

You mix two colorless solutions and the resulting mixture becomes cloudy. What type of reaction was observed?

chemistry change around us physical changes changes and their classification physical changes

  1. A physical reaction

  2. A redox reaction

  3. A precipitation reaction

  4. An acid base reactions.

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Correct Option: C
Explanation:

When two colourless solutions react to form a cloudy precipitate which settles at bottom of a solution then the reaction is said to be precipitation reaction.

Ex :- ${ AgNO } _{ 3 }+NaCl\rightarrow AgCl+{ NaNO } _{ 3 }$

Your lab partner mixed two colorless solutions in the test tube. He sees no observable changes in the resulting mixture and is unable to detect any change in temperature. Based on these observations, what type of reaction has taken place?

chemistry change around us physical changes changes and their classification physical changes

  1. A physical reaction

  2. A chemical reaction

  3. An exothermic reaction

  4. No reaction has taken place

Show answer
Correct Option: A
Explanation:

No change in temperature $-$ neither exothermic  or endothermic reaction.

as no observable change $-$  not a chemical reaction
since the liquid mixed $-$ it is a physical change.

Dissolving sugar in water is an example of:

chemistry change around us physical changes changes and their classification physical changes

  1. physical change

  2. chemical change

  3. neutralisation

  4. none of these

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Correct Option: A
Explanation:

Sugar dissolves in water is a physical change because in this change no new substance is formed and the process is reversible in which by vaporization followed by condensation and crystallization water and sugar can be separated.

When the hot metallic substance is cooled there is __________ in its volume.

chemistry change around us physical changes changes and their classification physical changes

  1. expantion

  2. contraction

  3. first contraction and then expansion

  4. no change in volume

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Correct Option: B
Explanation:

In general, the metallic substance expands on heating and contract on cooling.