Tag: physical changes

Questions Related to physical changes

Dissolving salt in water-is a/an:

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

  1. endothermic change

  2. exothermic change

  3. both A& B

  4. chemical combination

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Correct Option: A
Explanation:

When salt (solid crystal) is dissolved in water energy is required to break the intermolecular attraction between ions (Lattice energy). Hence the energy is collected from water which leads to a decrease in its temperature.

Hence endothermic reaction.

Adding sodium chloride to water is a:

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

  1. physical change

  2. chemical change

  3. chemical reaction

  4. none of these

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Correct Option: A
Explanation:

Adding sodium chloride to water is a physical change as the sodium chloride can be separated from water by evaporation.

Pooja took a candle in a vessel and heated the vessel. Even though the candle did not burn, it changed its shape and state. What kind of change is this?

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

  1. Naturalization

  2. Physical change

  3. Chemical change

  4. None of these

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Correct Option: B
Explanation:

Candle is made up of wax which melts on heating.When candle kept in a vessel and heated, the wax melts. When candle is allowed to cool, the wax solidifies. No new substance is formed. So, this is a physical change.

In a physical change :

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

  1. new substances are not formed

  2. reaction is reversible

  3. change is temporary

  4. All of the above

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Correct Option: D
Explanation:

Physical changes in a substance do not form new substances, these reactions are reversible and the change is temporary.

Physical changes are the changes affecting the form of a chemical substance, but not its chemical composition. They are used to separate mixtures into their component compounds, but cannot usually be used to separate compounds into chemical elements or simpler compounds.

Identify the substance that evaporates at room temperature.

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

  1. Water

  2. Oil

  3. Kerosene

  4. Ammonium chloride

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Correct Option: C

In early winter mornings, we can see drops of water on the blades of grass. This is because of :

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

  1. photosynthesis

  2. transpiration

  3. condensation

  4. water cycle

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Correct Option: C
Explanation:

Dew drops are formed due to condensation of water vapors. The air around us contains water vapors which we call moisture or humidity. Hot air contains more moisture as compared to cold air. During the night when the hot air comes into contact with some cold surface, water vapor present in it condenses on the cold surface in the form of droplets. These tiny drops of water are called dew drops.

Dissolution of carbon dioxide gas in water is  ________ change.

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

  1. chemical

  2. physical

  3. both of $A$ and $B$

  4. none of the above

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Correct Option: C
Explanation:

Dissolution of carbon dioxide gas in water is both a physical and chemical change.
Carbon dioxide dissolves in water producing carbonic acid, also known as soda water.
$ CO _2 + H _2O\rightarrow H _2CO _3$
There will be an equilibrium constant that will dictate the relative concentration of dissolved gas to the corresponding acid that is formed.
Usually nonmetal oxides like$CO _2, SO _2, NO _2$  simply dissolve in water, depending on the partial pressure above the water, and Henrys law constant. This implies a physical change.

Melting of wax is a _________ change.

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

  1. physical

  2. chemical

  3. both $A$ and $B$

  4. none of the above

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Correct Option: C
Explanation:

No new substances are formed. In a burning candle, there are both physical and chemical changes. The melting of the solid wax to form liquid wax and the evaporation of liquid wax to form wax vapour are physical changes. The burning of the wax vapour is a chemical change.

In ___________ , the properties of molecules remain same even after the change.

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

  1. physical change

  2. chemical change

  3. biochemical change

  4. photochemical change

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Correct Option: A
Explanation:

A physical change is any change in matter that involves the substance going from one physical state to another. 

The reference to a physical state involves solids, liquids, and gases. When a substance undergoes a physical change it does not lose its original properties because no new formation takes place when changing from one phase to another. The types of physical changes can vary. A substance can go from a solid to a liquid, a liquid to a gas, a gas to a liquid, a liquid to a solid, a solid to a gas, or a gas to a solid.

An iron ball at $\displaystyle { 50 }^{ \circ  }C$ is dropped in a beaker of water at $\displaystyle { 50 }^{ \circ  }C$. The heat will 

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

  1. Not flow from iron ball to water

  2. Not not flow from iron ball to water or from water to iron ball

  3. Not flow from water to iron ball

  4. Increase the temperature of both

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Correct Option: B
Explanation:

Energy flows always from a higher temperature to lower temperature. In this case there is no temperature  difference hence energy would not flow in any way.