Tag: changes and their classification

Questions Related to changes and their classification

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.

A mixture of sand and salt can be separated by:

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

  1. Sublimation

  2. Sieving

  3. Dissolving salt and sand mixture in water and then filtration

  4. Dissolving salt in water and then distillation

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Correct Option: D
Explanation:

Dissolving salt in water and then distillation
Process to separate sand and salt from the mixture :
Step 1: Add water to the mixture and stir until the salt dissolve.
Step 2: Turn your burner on and then keep the mixture over it.
Step 3: Pour the water mixture through a very fine strainer or cheese cloth filter . (Sand will remain in filter, salt and water will pass through it)
Step 4: Pour the water and salt mixture back into the burner . And allow the water to boil away and collect salt from there.

Match the columns


I II
(a) Physical change (i) Curdling of milk
(b) Chemical change (ii) Demagnetisation of magnets
(iii) Digestion of food
(iv) Crystallisation of substance
(v) Rusting of iron

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

  1. a - i, ii, iii, b - iv, v

  2. a - ii, iv, b - i, iii, iv

  3. a - ii, iv, b - i , iii, v

  4. a - iii, v, b - i, ii, iv

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Correct Option: C
Explanation:

A change in which only the physical properties of the substance gets changed, while its chemical composition remains unchanged, is called a physical change. Crystallisation of substance and Demagnetisation of magnets comes under this change.
A change in which chemical composition and chemical properties of the reacting substances undergo a change is called a chemical change.
Curdling of milk, Digestion of food, Rusting of iron etc. comes under chemical change.

Which of the following  laboratory technique would not bring a physical change in the components of a mixture?

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

  1. Chromatography

  2. Precipitation

  3. Filtering

  4. Distillation

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Correct Option: C
Explanation:

Physical change would not be in the components of a mixture by Filtering.
Filtering just separates solids from liquids. It does not involve any phase change.

$Ice\underset {cooling}{\overset {heating}{\rightleftharpoons}} water \underset {cooling}{\overset {heating}{\rightleftharpoons}} steam$. Identify the type of change

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

  1. Physical change

  2. Chemical change

  3. Both physical and chemical changes

  4. None

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Correct Option: A
Explanation:

In the given example, water only changes its state by the change in temperature, but its properties remain same hence it is an example of physical change not a chemical change.

Melting of butter is a physical change.

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

  1. True

  2. False

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Correct Option: A
Explanation:

Yes, melting of butter is a physical change because the butter can be solidified again (i.e. reversible change).

In melting of butter only state of the chemical substance is changed.