Tag: change around us

Questions Related to change around us

State whether true or false :

Cutting a log of wood into pieces is a chemical change.

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

  1. True

  2. False

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Correct Option: B
Explanation:

Cutting a log to wood into piece does not change the composition of wood hence it is not a chemical change.


It can be defined as physical irreversible change.

Hence the given statement is false.

Changes in which only ____________ properties of a substance change are called physical changes.

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

  1. chemical

  2. physical

  3. biological

  4. environmental

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Correct Option: B
Explanation:

Physical properties $-$ Shape, state of the substance size etc.

because these changes does not change the composition of the substance

Pick up the correct statement:

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

  1. Boiling points of alkyl halides are greater than those of the corresponding alkanes.

  2. In water, the solubility decreases as $CH _3OH > C _2H _5OH > C _6H _5OH$.

  3. Aniline is a weaker base than ammonia.

  4. All of the above.

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Correct Option: D
Explanation:

$(A)$  Boiling point $X$ molecular mass of compound hence alkyl halide have greater boiling point

$(B)$  More is the mass of the compound, less is the solubility.
               ${ CH } _{ 3 }OH>{ C } _{ 2 }{ H } _{ 5 }OH>{ C } _{ 6 }{ H } _{ 5 }OH$

$(C)$  Lone pair of aniline in resonance hence a weaker base.

Physical changes are ________.

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

  1. Temporary

  2. Permanent

  3. Irreversible

  4. Endothermic

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Correct Option: A
Explanation:

In a physical change, the substances are not altered chemically. No new products are formed. 
A physical change can affect the size, shape or color of a substance but does not affect its composition. The substances may be changed to another phase (i.e. gas, liquid, solid) or separated or combined so physical changes are temporary.

Examples:
when ice melts
when sulfur is mixed with iron filings. 
breaking a glass 
dissolving sugar in water

Which of them is not the characteristics of a physical change?

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

  1. Change in the physical properties

  2. New substances are formed

  3. Reversible reaction

  4. Original substance can be riveted back

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Correct Option: B
Explanation:

1) A physical change is temporary and is usually reversible.
2) No new substances are formed during a physical change.
3) There is no change in mass of the substance during a physical change.
4) There is no net absorption or release of energy during a physical change.

The process in which the state of a substance changes from solid to liquid is called:

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

  1. boiling

  2. condensation

  3. freezing

  4. melting

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Correct Option: D
Explanation:

When a solid is heated, the particles are given more energy and start to vibrate faster. At a certain temperature, the particles vibrate so much that their ordered structure breaks down. At this point the solid melts into liquid. This temperature change from solid to liquid is called  the melting point. Each solid has a set melting point at normal air pressure, but at higher altitudes the melting point lowers.

On decreasing temperature, a liquid turns into solid. This is:

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

  1. condensation

  2. melting

  3. freezing

  4. sublimation

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Correct Option: C
Explanation:

On decreasing temperature, a liquid turns in to solid, this process is called Freezing. Freezing or solidification is a phase transition state.
Most liquids freeze by crystallization. formation of crystalline solid from the uniform liquid. this is a first-order thermodynamic phase transition i.e as long as solid and liquid coexist the temperature of the whole system remains very nearly equal to the melting point due to slow removal of heat when in contact with the air, which is a poor heat conductor.

When a solid directly turns into gaseous state, it is called:

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

  1. sublimation

  2. condensation

  3. polymerisation

  4. melting

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Correct Option: A
Explanation:

Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. Sublimation is an endothermic phase transition that occurs at temperatures and pressures below a substance's triple point in its phase diagram. The reverse process of sublimation is desublimation or deposition.

Properties like shape, magnetic properties etc. are changed in:

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

  1. chemical change

  2. physical change

  3. Both A and B

  4. None of the above

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Correct Option: B
Explanation:

During a physical change, physical properties such as colour, volume, size, shape and magnetic properties etc. of the substances may change.

Dissolution of common salt or 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. both A and B

  4. none of the above

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Correct Option: A
Explanation:

A change in which only the physical properties of the substance get changed, when the chemical composition remain unchanged is called a physical change. Here we can obtain the sugar by boiling water.