7th Grade > Chemistry
PHYSICAL AND CHEMICAL CHANGES MCQs
Total Questions : 113
| Page 7 of 12 pages
Answer: Option A. ->
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Explanation: 1 Mark
Name of the process: 1 Mark
The exposed surface of sliced apples turn brown due to oxidation which is a chemical change.
Cutting of apples is a physical change as no chemical reaction takes place in this process.
Answer: Option A. ->
:
Examples: Formation of curd from milk, rusting of iron.
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Physical change definition: 1 Mark
Chemical change definition: 1 Mark
Examples: 1 Mark
Physical changes are the changes where the physical property of the substance varies without any formation of new products. These changes are reversible and the products are identical to the reactants.
Examples: Melting of ice, melting of wax.
Chemical changes are the changes where the chemical property of the substance varies with the formation of new products. These changes are irreversible and the products are not identical to the reactants.
Examples: Formation of curd from milk, rusting of iron.
Answer: Option A. ->
:
a) Type of change: 1 Mark
Irreversible change: 1 Mark
b) Answer: 1 Mark
When vinegar is mixed with baking soda, the release of carbon dioxide gas is seen in the form of bubbles.
We cannot get back our original substances since it is an irreversible change.
It is a chemical change because a new substance (carbon dioxide) is formed.
b) When carbon dioxide is passed through lime water, calcium carbonate is formed, which makes the lime water milky. The turning of lime water milky is a standard test for carbon dioxide.
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a) Type of change: 1 Mark
Irreversible change: 1 Mark
b) Answer: 1 Mark
When vinegar is mixed with baking soda, the release of carbon dioxide gas is seen in the form of bubbles.
We cannot get back our original substances since it is an irreversible change.
It is a chemical change because a new substance (carbon dioxide) is formed.
b) When carbon dioxide is passed through lime water, calcium carbonate is formed, which makes the lime water milky. The turning of lime water milky is a standard test for carbon dioxide.
Answer: Option A. ->
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Each part: 1.5 Marks
(a) Yes, the rusting of iron nails is faster in coastal areas than in desserts.
For rusting, the presence of both oxygen and water is essential.
In coastal areas humidity is much higher than in desserts.
The content of moisture in the air is more in coastal areas than in dessert. So the process of rusting becomes faster in coastal areas.
(b) The correct sequence of processes in water purification is:
Sedimentation - For removal of heavy particles.
Loading - For removal of the suspended particles.
Filtration - For removal of small particles which cannot be removed by sedimentation and loading.
Answer: Option A. ->
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Differences with examples: 5 Marks
PhysicalChemicalComposition of the substance does notComposition of the substance changes.change.Most changes are reversible.Most changes are irreversible.No new substances are formed, e.g,New substances are formed, e.g,Ice→Water→SteamBurning of Paper→AshesFor example, melting of ice, dissolving salt inFor example, rusting of iron, decay of foodwaterPhysical changes are those changes whichChemical changes involve change in chemicalinvolve change in only physical properties like,properties of the substances and change incolor, size, shape and state of substances etc.chemical composition also.
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Differences with examples: 5 Marks
PhysicalChemicalComposition of the substance does notComposition of the substance changes.change.Most changes are reversible.Most changes are irreversible.No new substances are formed, e.g,New substances are formed, e.g,Ice→Water→SteamBurning of Paper→AshesFor example, melting of ice, dissolving salt inFor example, rusting of iron, decay of foodwaterPhysical changes are those changes whichChemical changes involve change in chemicalinvolve change in only physical properties like,properties of the substances and change incolor, size, shape and state of substances etc.chemical composition also.
Answer: Option A. ->
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Working principle: 2 Marks
Example: 1 Mark
Distillation is a method used to separate two miscible liquids. When two liquids are miscible and the difference between their boiling point is high, then we use this method.
It is used to separate acetone and water. The boiling point of acetone is 56∘C, while that of water is 100∘C.
So, when we heat the mixture of acetone and water above 56∘C and below 100∘C, acetone gets evaporated and water remains.
In this way, the mixture of acetone and water gets separated.
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Working principle: 2 Marks
Example: 1 Mark
Distillation is a method used to separate two miscible liquids. When two liquids are miscible and the difference between their boiling point is high, then we use this method.
It is used to separate acetone and water. The boiling point of acetone is 56∘C, while that of water is 100∘C.
So, when we heat the mixture of acetone and water above 56∘C and below 100∘C, acetone gets evaporated and water remains.
In this way, the mixture of acetone and water gets separated.
Answer: Option A. ->
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Each correct answer: [1 Mark]
S.No
Change
Type of Change
1
Melting of Ice
Physical
2
Dissolving sugar in water
Physical
3
Burning rubber
Chemical
4
Burning camphor
Chemical
5
Melting Wax
Physical
:
Each correct answer: [1 Mark]
S.No
Change
Type of Change
1
Melting of Ice
Physical
2
Dissolving sugar in water
Physical
3
Burning rubber
Chemical
4
Burning camphor
Chemical
5
Melting Wax
Physical
Question 68.
Following are the observations of changes that have taken place. Classify them into chemical change or a physical change. [5 MARKS]
1. The change is temporary and can be reversed by changing the conditions in most of the cases.
2. New substance(s) is/are formed.
3. The chemical properties of the original substance remain the same.
4. There is an exchange of energy during this change which means that heat and light may be given out or absorbed.
5. As a result of the change, there may or may not be any change in the energy possessed by the original substance.
6. There is no change in the chemical composition of the original substance.
7. The change is permanent and cannot be reversed by changing the conditions or through ordinary physical processes.
8. There may or may not be any change in the state, size, shape, colour, and smell of the substance that undergoes this change.
9. The composition and the properties of the parent substance or substances change.
10. There is usually a change in the mass of the parent substance/s as well.
Answer: Option A. ->
:
Classification: 0.5 Mark each
Physical Change:
1. There is no change in the chemical composition of the original substance.
2. The change is temporary and can be reversed by changing the conditions in most of the cases.
3. The chemical properties of the original substance remain the same.
4. There may or may not be any change in the state, size, shape, colour, and smell of the substance that undergoes this change.
5. As a result of the change, there may or may not be any change in the energy possessed by the original substance.
Chemical change
1. New substance(s) is/are formed.
2. The composition and the properties of the parent substance or substances change.
3. The change is permanent and cannot be reversed by changing the conditions or through ordinary physical processes.
4. There is an exchange of energy during this change, which means that heat and light may be given out or absorbed.
5. There is usually a change in the mass of the of the parent substance/s as well.
:
Classification: 0.5 Mark each
Physical Change:
1. There is no change in the chemical composition of the original substance.
2. The change is temporary and can be reversed by changing the conditions in most of the cases.
3. The chemical properties of the original substance remain the same.
4. There may or may not be any change in the state, size, shape, colour, and smell of the substance that undergoes this change.
5. As a result of the change, there may or may not be any change in the energy possessed by the original substance.
Chemical change
1. New substance(s) is/are formed.
2. The composition and the properties of the parent substance or substances change.
3. The change is permanent and cannot be reversed by changing the conditions or through ordinary physical processes.
4. There is an exchange of energy during this change, which means that heat and light may be given out or absorbed.
5. There is usually a change in the mass of the of the parent substance/s as well.
Answer: Option A. ->
True
:
A
Food is chemically digested by enzymes. Once food has been broken down, the nutrients are sent into the bloodstream. Food undergoes many chemical changes before being absorbed by the body. Hence, digestion of food is a chemical change as the complex substances that we eat is changed into simpler substances.
:
A
Food is chemically digested by enzymes. Once food has been broken down, the nutrients are sent into the bloodstream. Food undergoes many chemical changes before being absorbed by the body. Hence, digestion of food is a chemical change as the complex substances that we eat is changed into simpler substances.
Answer: Option A. ->
CO2(g)+Ca(OH)2(aq)→CaCO3(s)+H2O(l)
:
A
:
A
When carbon dioxide is passed through limewater, calcium carbonate is formed. This makes the limewater turn milky. The reaction is as follows:
CO2(g)+Ca(OH)2(aq)→CaCO3(s)+H2O(l)
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