Chemical Changes and Reactions
Each subtopic includes About section, revision page link, 10 preview questions, and practice CTAs.
Physical vs Chemical Changes
SubtopicPhysical vs Chemical Changes under Chemical Changes and Reactions for Grade 7 ICSE.
Preview questions (no answers)
- 1.
Which of the following is a fast physical change?
A.Rusting of an iron gate
B.Breaking of a glass pane
C.Ripening of an apple
D.Formation of coal
- 2.
During which of these changes is the identity of the substance preserved?
A.Burning of paper
B.Dissolving salt in water
C.Souring of curd
D.Formation of rust
- 3.
The process of condensation (steam turning into water) is a:
A.Chemical change
B.Physical change
C.Irreversible change
D.Evolutionary change
- 4.
Which change is involved when a magnet attracts iron filings?
A.Chemical change
B.Physical change
C.Biological change
D.Permanent change
- 5.
Biogas is produced from animal waste by the action of anaerobic bacteria. This is a:
A.Physical change as the waste is just broken into smaller pieces.
B.Chemical change as new gases like methane are produced from organic matter.
C.Physical change as the smell of the waste remains the same.
D.Chemical change because the waste is being compressed.
- 6.
The burning of Liquefied Petroleum Gas (LPG) in a kitchen stove is a chemical change because:
A.The gas changes from a liquid in the cylinder to a gas in the pipe.
B.The fuel reacts with oxygen to produce heat, , and water vapor.
C.The flame can be extinguished by turning off the knob.
D.It is a reversible process.
- 7.
Adding a spoonful of copper sulfate powder to water and stirring it creates a clear blue liquid. This is a:
A.Chemical change because the color of the water changed.
B.Physical change because the copper sulfate can be recovered by evaporation.
C.Chemical change because the powder disappeared.
D.Physical change because the temperature of the water increased.
- 8.
Which of the following is NOT a reason why the formation of a solution (like salt in water) is considered a physical change?
A.No new substance is formed.
B.The constituents can be separated by physical means like evaporation.
C.The solution shows the properties of both salt and water.
D.The salt molecules undergo a permanent change in their chemical formula.
- 9.
A student lights a gas burner. The methane gas () reacts with oxygen () to produce and . This change is:
A.Physical, because the products are still gases.
B.Chemical, because the chemical bonds in methane and oxygen are broken and new bonds are formed in the products.
C.Physical, because the heat can be used to melt ice.
D.Chemical, because the mass of the gases increases.
- 10.
Which statement correctly describes the energy change in a physical change like the sublimation of dry ice ()?
A.Energy is released to the surroundings as bonds are formed.
B.Energy is absorbed from the surroundings to overcome intermolecular forces.
C.There is no energy change involved in sublimation.
D.Energy is created by the carbon dioxide molecules.
Download the worksheet for Chemical Changes and Reactions - Physical vs Chemical Changes to practice offline. It includes additional chapter-level practice questions.
Types of Chemical Reactions
SubtopicTypes of Chemical Reactions under Chemical Changes and Reactions for Grade 7 ICSE.
Preview questions (no answers)
- 1.
When iron powder and sulphur powder are heated together, they form iron sulphide. This is a:
A.Decomposition reaction
B.Combination reaction
C.Displacement reaction
D.Double Displacement reaction
- 2.
Which of these gases turns lime water milky?
A.Oxygen
B.Hydrogen
C.Carbon dioxide
D.Nitrogen
- 3.
In which reaction is energy taken in from the surroundings?
A.Exothermic
B.Endothermic
C.Burning
D.Neutralization
- 4.
The process of rusting of iron is an example of a slow:
A.Physical change
B.Chemical change
C.Reversible change
D.Endothermic change
- 5.
What remains behind when Sugar is heated strongly in a test tube?
A.White powder
B.Black carbon residue
C.Blue crystals
D.Yellow liquid
- 6.
Identify the type of reaction: .
A.Single displacement
B.Double displacement
C.Combination
D.Thermal decomposition
- 7.
Which of the following is NOT a characteristic of a chemical reaction?
A.Evolution of a gas
B.Formation of a precipitate
C.Change in state of matter without change in composition
D.Change in color
- 8.
The decomposition of calcium carbonate is an essential step in the manufacture of cement. What type of energy is primarily used for this decomposition?
A.Light energy
B.Electrical energy
C.Heat energy (Thermal)
D.Sound energy
- 9.
What happens when a piece of aluminum foil is added to a freshly prepared ferrous sulfate solution?
A.No reaction occurs as aluminum is less reactive
B.The green color of the solution fades and iron is displaced
C.The solution turns blue immediately
D.Aluminum dissolves and oxygen gas is evolved
- 10.
In the reaction between sodium thiosulfate and hydrochloric acid, a yellow turbidity appears. What is this yellow substance?
A.Sulfur dioxide gas
B.Colloidal sulfur
C.Sodium chloride
D.Hydrogen sulfide
Download the worksheet for Chemical Changes and Reactions - Types of Chemical Reactions to practice offline. It includes additional chapter-level practice questions.
Conditions for Chemical Changes
SubtopicConditions for Chemical Changes under Chemical Changes and Reactions for Grade 7 ICSE.
Preview questions (no answers)
- 1.
What happens to the rate of a reaction if the concentration of the reactants in a solution is increased?
A.It increases
B.It decreases
C.It stops
D.It remains unchanged
- 2.
Which of these processes requires light to occur?
A.Burning of paper
B.Photosynthesis in plants
C.Melting of wax
D.Digestion of food
- 3.
Which of the following is a characteristic of a catalyst?
A.It is consumed in the reaction
B.It changes the state of products
C.It remains chemically unchanged at the end
D.It provides energy to the reaction
- 4.
What is the condition required for the reaction between hydrogen and iodine to form hydrogen iodide?
A.Contact at room temperature
B.Heating
C.Electricity
D.Darkness
- 5.
What is the primary difference between a thermal decomposition and a photochemical decomposition?
A.One uses heat energy, the other uses light energy
B.One is reversible, the other is not
C.One occurs in solids, the other in gases
D.One requires a catalyst, the other does not
- 6.
Which condition is specifically required for the burning of a candle?
A.Supply of oxygen and reaching the ignition temperature
B.Presence of a metal catalyst
C.Exposure to ultraviolet light
D.Application of high external pressure
- 7.
Copper carbonate decomposes into copper oxide and carbon dioxide upon heating. What color change occurs during this reaction?
A.Blue to Green
B.Green to Black
C.Black to Red
D.Green to Blue
- 8.
If (phosphoric acid) is added to hydrogen peroxide, the rate of decomposition decreases. In this reaction, is called a:
A.Promoter
B.Inhibitor or Negative Catalyst
C.Reactant
D.Enzyme
- 9.
Which of the following is a condition required for the decomposition of Mercuric Oxide ()?
A.Exposure to intense light
B.High pressure
C.Strong heating
D.Presence of a promoter
- 10.
Why do some reactions like occur instantly without heating or any special condition other than mixing?
A.They are endothermic reactions
B.The reactants are already in the ionic state in solution
C.Water acts as a positive catalyst
D.The reaction is photochemical
Download the worksheet for Chemical Changes and Reactions - Conditions for Chemical Changes to practice offline. It includes additional chapter-level practice questions.
Energy Changes in Reactions
SubtopicEnergy Changes in Reactions under Chemical Changes and Reactions for Grade 7 ICSE.
Preview questions (no answers)
- 1.
Which of these is a similarity between respiration and burning coal?
A.Both are endothermic
B.Both require carbon dioxide
C.Both release energy (exothermic)
D.Both are physical changes
- 2.
What form of energy is primarily involved in the reaction of silver nitrate with light?
A.Heat energy
B.Light energy
C.Sound energy
D.Electrical energy
- 3.
In the chemical equation for an endothermic reaction, 'Heat' is usually written on which side?
A.The right side (products)
B.The left side (reactants)
C.Under the arrow
D.It is never written
- 4.
Which of the following is a common daily life example of an exothermic reaction?
A.Using a cold pack on an injury
B.Boiling water on a stove
C.Burning natural gas in a kitchen stove
D.Melting wax
- 5.
In the context of energy, how does a chemical reaction differ from most physical changes like melting ice?
A.Chemical reactions never involve energy changes.
B.Physical changes only involve the release of energy.
C.Chemical reactions involve energy changes due to breaking and forming of new bonds.
D.Physical changes involve the creation of new atoms with different energy.
- 6.
Which of the following is an endothermic chemical change?
A.Cooking of an egg
B.Burning of a matchstick
C.Respiration in human body
D.Formation of water from hydrogen and oxygen
- 7.
Which statement about energy in chemical reactions is correct?
A.Energy is always released in every chemical reaction.
B.Energy is always absorbed in every chemical reaction.
C.Chemical reactions always involve a change in energy.
D.Energy changes only happen in physical processes.
- 8.
In a closed system where an exothermic reaction occurs, what happens to the total mass and the total energy?
A.Total mass decreases and total energy increases.
B.Total mass remains the same and total energy remains the same (though it changes form).
C.Both mass and energy decrease as heat leaves the system.
D.Mass increases as the reaction absorbs heat.
- 9.
What distinguishes 'Photochemical reactions' from 'Thermolysis reactions' based on energy absorption?
A.Photochemical reactions release energy, Thermolysis absorbs it.
B.Photochemical reactions absorb light energy, while Thermolysis absorbs heat energy.
C.Photochemical reactions are physical, while Thermolysis is chemical.
D.There is no difference; both are names for exothermic reactions.
- 10.
Why does a teacher advise not to add water to concentrated acid, but rather add acid to water? (Relate to energy changes).
A.Adding water to acid is endothermic and would freeze the beaker.
B.The reaction is highly exothermic; adding water to acid can cause the small amount of water to boil instantly and splash.
C.Acid is a solid and water is a liquid, so the energy change is physical.
D.The energy released is used to create new acid molecules.
Download the worksheet for Chemical Changes and Reactions - Energy Changes in Reactions to practice offline. It includes additional chapter-level practice questions.