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CLASS VII SCIENCE
CLASS VII SCIENCE
CHAPTER V: CHANGES AROUND US: PHYSICAL AND CHEMICAL
CHAPTER V: CHANGES AROUND US: PHYSICAL AND CHEMICAL
Direct Questions Assertion / Reason Correct / Incorrect HOTS Challenging
DIRECT QUESTIONS
DIRECT QUESTIONS
A change in which a substance undergoes a change in its physical properties is called a:
A. Chemical change
B. Physical change
C. Biological change
D. Permanent change
Answer: B. Physical change
Which of the following is a chemical change?
A. Melting of wax
B. Dissolving sugar in water
C. Digestion of food
D. Shredding of paper
Answer: C. Digestion of food
The process of depositing a layer of zinc on iron is called:
A. Galvanization
B. Crystallization
C. Rusting
D. Neutralization
Answer: A. Galvanization
When magnesium ribbon burns, it produces a dazzling white flame and leaves behind:
A. Magnesium chloride
B. Magnesium oxide
C. Magnesium carbonate
D. Magnesium sulphate
Answer: B. Magnesium oxide
Which of the following is a physical change?
A. Rusting of iron
B. Burning of wood
C. Boiling of water
D. Cooking of vegetables
Answer: C. Boiling of water
Large crystals of pure substances can be obtained from their solutions by:
A. Galvanization
B. Crystallization
C. Oxidation
D. Sedimentation
Answer: B. Crystallization
Which gas turns lime water milky?
A. Oxygen
B. Hydrogen
C. Carbon dioxide
D. Nitrogen
Answer: C. Carbon dioxide
The brown film formed on the surface of iron when left in moist air is called:
A. Dust
B. Rust
C. Zinc
D. Carbon
Answer: B. Rust
Which of the following are the two essential requirements for rusting?
A. Nitrogen and Water
B. Oxygen and Water
C. Carbon dioxide and Water
D. Oxygen and Nitrogen
Answer: B. Oxygen and Water
What kind of change is the explosion of a firework?
A. Physical change
B. Chemical change
C. Reversible change
D. No change
Answer: B. Chemical change
The chemical name of baking soda is:
A. Sodium carbonate
B. Sodium hydrogen carbonate
C. Calcium carbonate
D. Sodium hydroxide
Answer: B. Sodium hydrogen carbonate
A change that can be reversed to get the original substance back is a:
A. Chemical change
B. Irreversible change
C. Physical change
D. Periodic change
Answer: C. Physical change
When carbon dioxide is passed through lime water, it turns milky due to the formation of:
A. Calcium oxide
B. Calcium carbonate
C. Calcium bicarbonate
D. Calcium hydroxide
Answer: B. Calcium carbonate
Which of the following is an irreversible chemical change?
A. Folding a paper
B. Stretching a rubber band
C. Curdling of milk
D. Melting of ice
Answer: C. Curdling of milk
In a physical change, which of the following properties may change?
A. Shape and size
B. Color
C. State
D. All of the above
Answer: D. All of the above
Which of the following is NOT a characteristic of a chemical change?
A. Evolution of gas
B. Change in smell
C. Formation of a new substance
D. No heat is ever involved
Answer: D. No heat is ever involved
Iron + Oxygen + Water yields:
A. Iron oxide (Rust)
B. Iron hydroxide
C. Iron chloride
D. Iron carbonate
Answer: A. Iron oxide (Rust)
Crystallization is an example of a:
A. Chemical change
B. Physical change
C. Biological change
D. Irreversible change
Answer: B. Physical change
Which of the following prevents rusting of iron?
A. Keeping it in water
B. Painting the surface
C. Keeping it in moist air
D. Heating it
Answer: B. Painting the surface
What happens when vinegar reacts with baking soda?
A. Oxygen is evolved
B. Carbon dioxide is evolved
C. Hydrogen is evolved
D. Nitrogen is evolved
Answer: B. Carbon dioxide is evolved
Photosynthesis is a:
A. Physical change
B. Chemical change
C. Reversible change
D. Temporary change
Answer: B. Chemical change
The process of changing water into water vapor is:
A. Condensation
/B. Evaporation
C. Sublimation
D. Freezing
Answer: B. Evaporation
Which of the following is a slow chemical change?
A. Burning of a matchstick
B. Rusting of iron
C. Explosion of a bomb
D. Tearing of paper
Answer: B. Rusting of iron
Ozone layer protects us from:
A. Infrared radiation
B. Ultraviolet radiation
C. Visible light
D. X-rays
Answer: B. Ultraviolet radiation
Which of the following describes the change when an apple slice turns brown?
A. Physical change
B. Chemical change
C. Reversible change
D. Crystallization
Answer: B. Chemical change
Chopping of wood is a ________ change, while burning of wood is a ________ change.
A. Physical, Chemical
B. Chemical, Physical
C. Physical, Physical
D. Chemical, Chemical
Answer: A. Physical, Chemical
Rusting is faster in:
A. Desert areas
B. Coastal areas
C. Hilly areas
D. Cold storage
Answer: B. Coastal areas
Which of the following is a method to obtain common salt from sea water?
A. Galvanization
B. Evaporation
C. Crystallization
D. Both B and C
Answer: D. Both B and C
In which type of change is energy usually absorbed or evolved?
A. Only physical change
B. Only chemical change
C. Both physical and chemical changes
D. Neither
Answer: C. Both physical and chemical changes (Though more prominent in chemical)
Setting of curd is a:
A. Physical change
B. Chemical change
C. Reversible change
D. Slow physical change
Answer: B. Chemical change
Which metal is often mixed with iron to make stainless steel?
A. Chromium and Nickel
B. Copper and Zinc
C. Gold and Silver
D. Aluminium and Lead
Answer: A. Chromium and Nickel
When magnesium oxide is dissolved in water, it forms:
A. Magnesium chloride
B. Magnesium hydroxide
C. Magnesium carbonate
D. Magnesium sulphate
Answer: B. Magnesium hydroxide
Tearing a piece of paper is a physical change because:
A. It is reversible
B. No new substance is formed
C. It is very fast
D. Its color changes
Answer: B. No new substance is formed
What is the color of the solution when iron nails are placed in copper sulphate solution?
A. Stays blue
B. Turns green
C. Turns red
D. Turns colorless
Answer: B. Turns green
When iron reacts with copper sulphate, the brown deposit on the iron nail is:
A. Iron oxide
B. Copper
C. Zinc
D. Sulphur
Answer: B. Copper
Which of the following is an example of condensation?
A. Ice melting
B. Water boiling
C. Dew drops on grass
D. Burning of wax
Answer: C. Dew drops on grass
Burning of any substance is always a:
A. Physical change
B. Chemical change
C. Reversible change
D. Cooling process
Answer: B. Chemical change
What change occurs when we stretch a spring?
A. Chemical change
B. Physical change
C. Permanent change
D. Biological change
Answer: B. Physical change
Which of the following is a man-made chemical change?
A. Ripening of fruit
B. Digestion
C. Making of plastic
D. Weathering of rocks
Answer: C. Making of plastic
The chemical formula of Magnesium Hydroxide is:
A. MgO
B. Mg(OH)₂
C. MgCl₂
D. MgCO₃
Answer: B. Mg(OH)₂
Formation of manure from leaves is a:
A. Physical change
B. Chemical change
C. Reversible change
D. Fast change
Answer: B. Chemical change
Which of the following does NOT happen during a chemical change?
A. Production of sound
B. Production of heat
C. Change in mass of the system (law of conservation)
D. Change in color
Answer: C. Change in mass of the system (Mass is conserved, though it seems to change if gases escape)
The gas we use in the kitchen is called Liquefied Petroleum Gas (LPG). In the cylinder it exists as a liquid. When it comes out from the cylinder it becomes a gas (Change–A) then it burns (Change–B).
A. Process – A is a chemical change.
B. Process – B is a chemical change.
C. Both A and B are chemical changes.
D. None of these processes is a chemical change.
Answer: B. Process – B is a chemical change.
Anaerobic bacteria digest animal waste and produce biogas (Change–A). The biogas is then burnt as fuel (Change–B).
A. Process – A is a chemical change.
B. Process – B is a chemical change.
C. Both A and B are chemical changes.
D. None of these processes is a chemical change.
Answer: C. Both A and B are chemical changes.
Heating of a hacksaw blade is a:
A. Physical change
B. Chemical change
C. Irreversible change
D. Biological change
Answer: A. Physical change
Breaking of a glass tumbler is a:
A. Physical change
B. Chemical change
C. Reversible change
D. Periodic change
Answer: A. Physical change
Which of the following is a characteristic of crystallization?
A. It is a chemical change.
B. It is used to purify solids.
C. It results in the formation of a new substance.
D. It is an irreversible process.
Answer: B. It is used to purify solids.
A shiny metal 'M' on burning gives a white ash 'W'. 'W' on dissolving in water gives a solution that turns red litmus blue. 'M' is:
A. Iron
B. Copper
C. Magnesium
D. Aluminium
Answer: C. Magnesium
Which of the following is a chemical change involving light?
A. Glowing of a bulb
B. Photosynthesis
C. Melting of ice
D. Breaking of a mirror
Answer: B. Photosynthesis
Rusting can be prevented by:
A. Greasing
B. Painting
C. Galvanizing
D. All of the above
Answer: D. All of the above
ASSERTION AND REASON
ASSERTION AND REASON
A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true but R is not the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.
Assertion (A): Melting of ice is a physical change.
Reason (R): The chemical composition of water remains the same in both ice and liquid water.
Answer: A. Both A and R are true and R is the correct explanation of A.
Assertion (A): Iron objects rust faster in coastal areas.
Reason (R): The air in coastal areas contains high moisture and salt, which speeds up rusting.
Answer: A. Both A and R are true and R is the correct explanation of A.
Assertion (A): Burning of a candle is both a physical and chemical change.
Reason (R): Melting of wax is physical, and burning of wax is chemical.
Answer: A. Both A and R are true and R is the correct explanation of A.
Assertion (A): Galvanization is the process of coating iron with copper.
Reason (R): Copper prevents the iron from rusting.
Answer: D. A is false but R is true. (Correction: Galvanization uses Zinc).
Assertion (A): Cooking of food is a chemical change.
Reason (R): Raw vegetables cannot be obtained back from cooked food.
Answer: A. Both A and R are true and R is the correct explanation of A.
Assertion (A): Magnesium hydroxide is an acid.
Reason (R): It turns red litmus paper blue.
Answer: D. A is false but R is true.
Assertion (A): Digestion is a chemical change.
Reason (R): During digestion, food is broken down into simpler substances with the help of enzymes.
Answer: A. Both A and R are true and R is the correct explanation of A.
Assertion (A): Crystallization is a chemical change.
Reason (R): Pure crystals are formed from a solution.
Answer: D. A is false but R is true.
Assertion (A): Cutting a log of wood into small pieces is a physical change.
Reason (R): No new substance is formed, only the size and shape change.
Answer: A. Both A and R are true and R is the correct explanation of A.
Assertion (A): Passing CO₂ through lime water is a physical change.
Reason (R): A white precipitate of calcium carbonate is formed.
Answer: D. A is false but R is true.
CORRECT / INCORRECT STATEMENTS
CORRECT / INCORRECT STATEMENTS
Which of the following statements is INCORRECT?
A. Rusting is a chemical change.
B. Cutting of wood is a chemical change.
C. Formation of manure from leaves is a chemical change.
D. Dissolving sugar in water is a physical change.
Answer: B. Cutting of wood is a chemical change.
Identify the CORRECT statement:
A. Physical changes are generally irreversible.
B. Chemical changes result in the formation of new substances.
C. Rusting requires only oxygen.
D. Setting of curd is a physical change.
Answer: B. Chemical changes result in the formation of new substances.
Which of the following about crystallization is CORRECT?
A. It is a chemical change.
B. It is used to get large crystals of pure substances.
C. It requires very high pressure.
D. It always produces a gas.
Answer: B. It is used to get large crystals of pure substances.
Find the INCORRECT statement:
A. Photosynthesis is a chemical change.
B. Digestion is a physical change.
C. Burning of coal is a chemical change.
D. Melting of wax is a physical change.
Answer: B. Digestion is a physical change.
Which statement about Magnesium ribbon burning is CORRECT?
A. It is a physical change.
B. The ash formed is Magnesium Oxide.
C. It turns blue litmus red.
D. It is a reversible change.
Answer: B. The ash formed is Magnesium Oxide.
Identify the INCORRECT statement regarding rusting:
A. Salt water slows down the rate of rusting.
B. Painting prevents rusting.
C. Moisture is necessary for rusting.
D. Chromium is used in making stainless steel to prevent rust.
Answer: A. Salt water slows down the rate of rusting.
Which of the following is CORRECT regarding chemical changes?
A. Only heat is produced.
B. New substances are always formed.
C. They are always reversible.
D. The smell of the substance never changes.
Answer: B. New substances are always formed.
Select the CORRECT statement about Ozone:
A. It is a physical barrier only.
B. Its breakdown into oxygen is a chemical change.
C. It allows UV rays to reach Earth.
D. It is found in the core of the Earth.
Answer: B. Its breakdown into oxygen is a chemical change.
Identify the INCORRECT statement:
A. Mixing baking soda and vinegar produces CO₂.
B. Lime water turns milky due to Calcium carbonate.
C. Stretching a rubber band is a chemical change.
D. Melting of ice is reversible.
Answer: C. Stretching a rubber band is a chemical change.
Which statement is CORRECT?
A. A physical change involves the formation of a new substance.
B. An iron nail dipped in copper sulphate solution becomes coated with copper.
C. Burning of a magnesium ribbon is a physical change.
D. Galvanization is used to prevent the rusting of copper.
Answer: B. An iron nail dipped in copper sulphate solution becomes coated with copper.
HOTS (HIGHER ORDER THINKING SKILLS)
HOTS (HIGHER ORDER THINKING SKILLS)
Why does a cut apple turn brown if left in the open for some time?
A. It absorbs dust from the air.
B. The iron in the apple reacts with oxygen in the air to form iron oxide (chemical change).
C. The apple is losing its water.
D. It is a physical change of color.
Answer: B. The iron in the apple reacts with oxygen in the air to form iron oxide (chemical change).
If you dissolve sugar in hot water and then cool it down, you might see sugar crystals again. Is this a chemical change?
A. Yes, because crystals are new substances.
B. No, it is a physical change because the sugar's chemical identity remains the same.
C. Yes, because it is irreversible.
D. No, because it involves heat.
Answer: B. No, it is a physical change because the sugar's chemical identity remains the same.
Why is the rusting of an iron ship a major problem even if it is painted?
A. The paint keeps the ship too heavy.
B. Part of the ship remains underwater, and salt in sea water makes the process of rust formation faster.
C. The ship's metal is different from land iron.
D. Fish eat the rust.
Answer: B. Part of the ship remains underwater, and salt in sea water makes the process of rust formation faster.
When we breathe out into a tube of lime water, it turns milky. This proves that:
A. We inhale carbon dioxide.
B. We exhale carbon dioxide, which reacts chemically with lime water.
C. Our breath contains milk.
D. Breathing is a physical change.
Answer: B. We exhale carbon dioxide, which reacts chemically with lime water.
Why is the burning of a candle considered both a physical and chemical change?
A. Because the candle changes its color.
B. Because wax melts (physical) and wax vapor burns to form CO₂ and water (chemical).
C. Because it produces light and sound.
D. Because it is reversible.
Answer: B. Because wax melts (physical) and wax vapor burns to form CO₂ and water (chemical).
If you have a mixture of iron filings and sulphur powder, you can separate them with a magnet (Physical change). But if you heat them, they form Iron Sulphide. Why can't you use a magnet then?
A. The magnet loses its power.
B. A chemical change occurred forming a new substance that is not magnetic.
C. The sulphur covers the iron.
D. The heat destroyed the iron.
Answer: B. A chemical change occurred forming a new substance that is not magnetic.
Why do we say that the breakdown of Ozone is a chemical change?
A. Because it changes into Oxygen, which is a different substance.
B. Because it happens in the sky.
C. Because it involves the Sun.
D. Because it is a very fast physical change.
Answer: A. Because it changes into Oxygen, which is a different substance.
What happens to the weight of an iron object after it rusts?
A. It decreases.
B. It increases because oxygen and water are added to the iron.
C. It remains the same.
D. It becomes zero.
Answer: B. It increases because oxygen and water are added to the iron.
Why is galvanization not used for food cans?
A. Zinc is too expensive.
B. Zinc might react with acidic food and become toxic; instead, tinning is used.
C. Zinc is a non-metal.
D. Zinc makes the food taste like iron.
Answer: B. Zinc might react with acidic food and become toxic; instead, tinning is used.
Why does a magnesium ribbon burn more easily if it is cleaned with sandpaper first?
A. Sandpaper adds chemicals to it.
B. It removes the protective layer of magnesium oxide so the metal can react with oxygen.
C. It makes the ribbon thinner.
D. It creates friction and heat.
Answer: B. It removes the protective layer of magnesium oxide so the metal can react with oxygen.
CHALLENGING QUESTIONS
CHALLENGING QUESTIONS
Which of the following is a chemical change where both heat and light are produced?
A. Photosynthesis
B. Rusting
C. Burning of LPG
D. Evaporation
Answer: C. Burning of LPG
When blue vitriol (Copper Sulphate) crystals are heated, they turn white. This is due to:
A. Formation of a new substance.
B. Loss of water of crystallization (Physical change).
C. Oxidation of copper.
D. Melting of the crystals.
Answer: B. Loss of water of crystallization (Physical change).
Which of the following processes involves both physical and chemical changes?
A. Digestion of food
B. Burning of a candle
C. Crystallization
D. Both A and B
Answer: D. Both A and B (Digestion involves mechanical chewing-physical, and enzyme action-chemical).
In which of the following cases is a new substance NOT formed?
A. Burning of magnesium
B. Rusting of iron
C. Dissolving common salt in water
D. Passing CO₂ through lime water
Answer: C. Dissolving common salt in water
The process of browning of cut vegetables can be minimized by:
A. Adding vinegar or lemon juice (acid).
B. Keeping them in water.
C. Boiling them.
D. All of the above.
Answer: D. All of the above.
Which of the following is a characteristic of a reversible physical change?
A. Formation of a new substance.
B. Change in chemical properties.
C. Ability to regain the original substance.
D. Evolution of a gas.
Answer: C. Ability to regain the original substance.
What is the chemical composition of the "milkiness" in lime water?
A. Calcium hydroxide
B. Calcium carbonate
C. Calcium oxide
D. Calcium bicarbonate
Answer: B. Calcium carbonate
Which of the following is an example of an exothermic chemical change?
A. Photosynthesis
B. Respiration
C. Melting of ice
D. Evaporation of water
Answer: B. Respiration (Releases energy).
The color change in the reaction between iron and copper sulphate is from:
A. Green to Blue
B. Blue to Green
C. Colorless to Red
D. Blue to Colorless
Answer: B. Blue to Green
Crystallization is used to obtain:
A. Pure liquid from a solid.
B. Pure solid from its solution.
C. Gas from a liquid.
D. Two liquids from a mixture.
Answer: B. Pure solid from its solution.
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