🔹 Very Short Answer Type Questions (1–15)
Q1. State whether the following statement is true or false: Milk is a pure substance.
Ans: False
Q2. Name three mixtures found in nature.
Ans: Air, Soil, Sea water
Q3. Which of the following is a mixture? Salt, Air, Water, Alum, Sugar
Ans: Air
Q4. Name one metal and one non-metal which exist as liquids at room temperature.
Ans:
Metal – Mercury
Non-metal – Bromine
Q5. Name a metal which is soft and a non-metal which is hard.
Ans:
Metal – Sodium
Non-metal – Diamond
Q6. Name a non-metal which is a good conductor of electricity.
Ans: Graphite
Q7. Name a liquid which can be classified as a pure substance and conducts electricity.
Ans: Mercury
Q8. Name one solid, one liquid and one gaseous non-metal.
Ans:
Solid – Sulphur
Liquid – Bromine
Gas – Oxygen
Q9. Name the property:
(a) which allows metals to be hammered into thin sheets.
Ans: Malleability
(b) which enables metals to be drawn into wires.
Ans: Ductility
Q10. Which type of elements, metals or non-metals, show the property of brittleness?
Ans: Non-metals
Q11. What is meant by saying that metals are malleable and ductile?
Ans: Metals can be beaten into thin sheets and drawn into wires.
Q12. What is meant by saying that non-metals are brittle?
Ans: Non-metals break easily into pieces when hammered.
Q13. What is meant by saying that metals are sonorous?
Ans: Metals produce a ringing sound when struck.
Q14. What is meant by saying that metals are lustrous?
Ans: Metals have a shiny surface.
Q15. What is the general name of the materials which contain at least two pure substances and show the properties of their constituents?
Ans: Mixtures
🔹 Answers (Q16–45)
Q16. “The properties of the product are different from those of the constituents”. State whether this statement best describes an element, a compound or a mixture.
Ans: Compound
Q17. Name one element, one compound and one mixture.
Ans:
Element – Iron
Compound – Water
Mixture – Air
Q18. What is the major difference between a solution and an ordinary mixture?
Ans:
A solution is a homogeneous mixture, whereas an ordinary mixture may be heterogeneous.
Q19. What name is given to those elements which are neither good conductors of electricity like copper nor insulators like sulphur?
Ans: Metalloids
Q20. Fill in the blanks:
(a) An element is made up of only one kind of atoms.
(b) Brine is a mixture whereas alcohol is a compound.
(c) Brass is an alloy which is considered a mixture.
(d) The three important metalloids are Boron, Silicon and Germanium.
(e) The elements which are sonorous are called metals.
🔹 Short Answer Type Questions
Q21. Classify the following into elements and compounds: H₂O, He, Cl₂, CO, Co
Ans:
Elements – He, Cl₂, Co
Compounds – H₂O, CO
Q22. Classify the following as elements or compounds:
Iron, Iron sulphide, Sulphur, Chalk, Washing soda, Sodium, Carbon, Urea
Ans:
Elements – Iron, Sulphur, Sodium, Carbon
Compounds – Iron sulphide, Chalk, Washing soda, Urea
Q23. What elements do the following compounds contain? Sugar, Common salt
Ans:
Sugar – Carbon, Hydrogen, Oxygen
Common salt – Sodium, Chlorine
Q24. What are pure substances? Give two examples.
Ans:
Pure substances are made up of only one kind of particles.
Examples: Gold, Water
Q25. What are the two types of pure substances? Give one example of each type.
Ans:
Types: Elements and Compounds
Element – Iron
Compound – Water
Q26. Which of the following are ‘pure substances’?
Ice, Milk, Iron, Hydrochloric acid, Calcium oxide, Mercury, Brick, Wood, Air
Ans:
Ice, Iron, Hydrochloric acid, Calcium oxide, Mercury
Q27. What is the other name for impure substances? Give two examples.
Ans:
Mixtures
Examples: Air, Milk
Q28. Which of the following substances are elements?
Water, Salt, Mercury, Iron, Marble, Diamond, Wood, Nitrogen, Air, Graphite, Hydrogen, Oxygen, Sugar, Chlorine
Ans:
Mercury, Iron, Diamond, Nitrogen, Graphite, Hydrogen, Oxygen, Chlorine
Q29. State three reasons why you think air is a mixture and water is a compound.
Ans:
Air (mixture):
Variable composition
Components can be separated
No fixed boiling point
Water (compound):
Fixed composition
Cannot be separated by physical methods
Has definite properties
Q30. Name two solid, two liquid and two gaseous elements at room temperature.
Ans:
Solid – Iron, Carbon
Liquid – Mercury, Bromine
Gas – Oxygen, Nitrogen
Q31. Explain why hydrogen and oxygen are considered elements whereas water is not considered an element.
Ans:
Hydrogen and oxygen consist of only one type of atoms, so they are elements.
Water is made of two elements chemically combined, so it is a compound.
Q32. What are the three groups into which all the elements can be divided? Name two elements belonging to each group.
Ans:
Metals – Iron, Copper
Non-metals – Oxygen, Sulphur
Metalloids – Silicon, Germanium
Q33. State two physical properties on the basis of which metals can be distinguished from non-metals.
Ans:
Conductivity
Malleability
Q34. Compare the properties of metals and non-metals with respect to (i) malleability (ii) ductility (iii) electrical conductivity.
Ans:
Metals – malleable, ductile, good conductors
Non-metals – brittle, non-ductile, poor conductors
Q35. State any two properties for believing that aluminium is a metal.
Ans:
Good conductor of electricity
Malleable
Q36. Give reason why:
(a) Copper metal is used for making electric wires.
Ans: Because it is a good conductor and ductile
(b) Graphite is used for making electrode in a dry cell.
Ans: Because it conducts electricity
Q37. How would you confirm that a colourless liquid given to you is pure water?
Ans:
By checking its boiling point (100°C)
Q38. Choose the solutions from among the following mixtures:
Soil, Sea-water, Air, Coal, Soda-water
Ans:
Sea-water, Air, Soda-water
Q39. Is air a mixture or a compound? Give three reasons for your answer.
Ans:
Air is a mixture because:
Variable composition
Components can be separated
No fixed properties
Q40. Give two reasons for supposing that water is a compound and not a mixture.
Ans:
Fixed composition
Cannot be separated by physical methods
Q41. Define a compound. Give two points of evidence to show that sodium chloride is a compound.
Ans:
Compound: Substance formed by chemical combination
Evidence:
Fixed composition
Cannot be separated physically
Q42. Define a mixture. Give two points of evidence to show that sugar solution is a mixture.
Ans:
Mixture: Physical combination of substances
Evidence:
Components can be separated
Variable composition
Q43. State two reasons for supposing that brass is a mixture and not a compound.
Ans:
Variable composition
Components retain properties
Q44. List five characteristics by which compounds can be distinguished from mixtures.
Ans:
Fixed composition
Chemical combination
New properties
Not separable physically
Definite melting/boiling point
Q45. Explain why a solution of salt in water is considered a mixture and not a compound.
Ans:
Because:
It is a physical combination
Components retain properties
Can be separated by evaporation
🔹 Answers (Q46–55)
Q46. State one property in which a solution of sugar in water resembles a mixture of sugar and sand, and one property in which it differs from it.
Ans:
Resemblance: Both are mixtures.
Difference: Sugar solution is homogeneous, while sugar and sand mixture is heterogeneous.
Q47. You are given two liquids, one a solution and the other a compound. How will you distinguish the solution from the compound?
Ans:
A solution can be separated by physical methods (like evaporation), while a compound cannot be separated by physical methods.
Q48. Name a non-metal:
(a) which is lustrous
Ans: Iodine
(b) which is required for combustion
Ans: Oxygen
(c) whose one of the allotropic forms is a good conductor of electricity. Name the allotrope.
Ans: Carbon – Graphite
(d) other than carbon which shows allotropy
Ans: Sulphur
(e) which is known to form the largest number of compounds
Ans: Carbon
Q49. Name a metal:
(a) which can be easily cut with a knife
Ans: Sodium
(b) which forms amalgams
Ans: Mercury
(c) which has no fixed shape
Ans: Mercury
(d) which has a low melting point
Ans: Gallium
(e) which is yellow in colour
Ans: Gold
Q50. Which of the following are not compounds?
Chlorine gas, Potassium chloride, Iron powder, Iron sulphide, Aluminium foil, Iodine vapour, Graphite, Carbon monoxide, Sulphur powder, Diamond
Ans:
Chlorine gas, Iron powder, Aluminium foil, Iodine vapour, Graphite, Sulphur powder, Diamond
🔹 Long Answer Type Questions
Q51 (a). State the main points of difference between homogeneous and heterogeneous mixtures.
Ans:
| Homogeneous Mixture | Heterogeneous Mixture |
|---|---|
| Uniform composition | Non-uniform composition |
| Single phase | Two or more phases |
| Components not visible | Components visible |
Q51 (b). Classify the following materials as homogeneous and heterogeneous mixtures:
Soda-water, Wood, Air, Soil, Vinegar, Alcohol and water mixture, Petrol and water mixture, Chalk and water mixture, Sugar and water mixture, Copper sulphate solution
Ans:
Homogeneous: Soda-water, Air, Vinegar, Alcohol + water, Sugar solution, Copper sulphate solution
Heterogeneous: Wood, Soil, Petrol + water, Chalk + water
Q52 (a). What is meant by (i) elements (ii) compounds and (iii) mixtures? Write two examples of each.
Ans:
Element: Pure substance made of one type of atom (Iron, Oxygen)
Compound: Chemically combined substances (Water, Carbon dioxide)
Mixture: Physical combination (Air, Soil)
Q52 (b). Classify the following into elements, compounds and mixtures:
Marble, Air, Gold, Brass, Sand, Diamond, Graphite, Petroleum, Common salt, Sea-water, Chalk
Ans:
Elements: Gold, Diamond, Graphite
Compounds: Marble, Sand, Common salt, Chalk
Mixtures: Air, Brass, Petroleum, Sea-water
Q53 (a). What are (i) metals (ii) non-metals and (iii) metalloids? Give two examples each.
Ans:
Metals: Good conductors (Iron, Copper)
Non-metals: Poor conductors (Oxygen, Sulphur)
Metalloids: Intermediate properties (Silicon, Germanium)
Q53 (b). Classify the following into metals, non-metals and metalloids:
Silicon, Mercury, Diamond, Sulphur, Iodine, Germanium, Sodium, Carbon, Magnesium, Copper, Boron, Helium
Ans:
Metals: Mercury, Sodium, Magnesium, Copper
Non-metals: Diamond, Sulphur, Iodine, Carbon, Helium
Metalloids: Silicon, Germanium, Boron
Q54 (a). What is a mixture? Give two examples.
Ans:
A mixture is a physical combination of substances.
Examples: Air, Soil
Q54 (b). What is meant by (i) homogeneous mixtures and (ii) heterogeneous mixtures? Give two examples each.
Ans:
Homogeneous: Uniform composition (Salt water, Air)
Heterogeneous: Non-uniform (Sand + water, Oil + water)
Q54 (c). What is the other name of homogeneous mixtures?
Ans: Solutions
Q55 (a). What are the three general classes of matter? Give one example of each type.
Ans:
The three general classes of matter are:
Elements – Example: Iron
Compounds – Example: Water
Mixtures – Example: Air
Q55 (b). Draw a flow-chart for the schematic representation of different types of matter.
Ans:
Matter
→ Pure substances → Elements / Compounds
→ Mixtures → Homogeneous / Heterogeneous
Q56. Which of the following is not an element?
(a) graphite (b) germanium (c) silica (d) silicon
Ans: (c) silica
Q57. Which of the following are compounds?
(i) CO (ii) NO (iii) NO (iv) Co
Options:
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (ii) and (iv)
Ans: (c) (i) and (iii)
Q58. One of the following substances is neither a good conductor of electricity nor an insulator. This substance is:
(a) chromium (b) germanium (c) gallium (d) potassium
Ans: (b) germanium
🔹 Answers (Q59–72)
Q59. Which of the following is not a mixture?
(a) kerosene (b) air (c) alcohol (d) petrol
Ans: (c) alcohol
Q60. The element which is not common between the compounds called baking soda and soda ash is
(a) sodium (b) hydrogen (c) oxygen (d) carbon
Ans: (b) hydrogen
Q61. “Is malleable and ductile” best describes:
(a) a solution (b) a metal (c) a compound (d) a non-metal
Ans: (b) a metal
Q62. Which one of the following is not a metalloid?
(a) boron (b) silicon (c) gallium (d) germanium
Ans: (c) gallium
Q63. The elements which normally exist in the liquid state are:
(a) bromine and iodine
(b) mercury and chlorine
(c) iodine and mercury
(d) bromine and mercury
Ans: (d) bromine and mercury
Q64. When a mixture of iron powder and sulphur powder is heated strongly to form iron sulphide, then heat energy is:
(a) released
(b) first absorbed and then released
(c) absorbed
(d) neither absorbed nor released
Ans: (a) released
Q65. The property/properties which enable copper metal to be used for making electric wires is/are:
(a) copper metal is malleable and ductile
(b) copper metal is a good conductor of electricity
(c) copper metal is ductile and has low electrical resistance
(d) copper metal is sonorous and an excellent conductor of electricity
Ans: (c) copper metal is ductile and has low electrical resistance
Q66. On the basis of composition of matter, milk is considered to be:
(a) a pure substance
(b) an impure substance
(c) an element
(d) a compound
Ans: (b) an impure substance
Q67. Which of the following statements are true for pure substances?
(i) pure substances contain only one kind of particles
(ii) pure substances may be compounds or mixtures
(iii) pure substances have the same composition throughout
(iv) pure substances can be exemplified by all elements other than nickel
Options:
(a) (i) and (ii)
(b) (i) and (iii)
(c) (iii) and (iv)
(d) (ii) and (iii)
Ans: (b) (i) and (iii)
Q68. Which of the following are homogeneous in nature?
(i) ice (ii) wood (iii) soil (iv) air
Options:
(a) (i) and (iii)
(b) (ii) and (iv)
(c) (i) and (iv)
(d) (iii) and (iv)
Ans: (c) (i) and (iv)
Q69. X + Y → P (X and Y cannot be broken down by chemical reactions)
Which statements are correct?
(i) P is a compound
(ii) X and Y are compounds
(iii) X and Y are elements
(iv) P has a fixed composition
Options:
(a) (i), (ii) and (iii)
(b) (i), (ii) and (iv)
(c) (ii), (iii) and (iv)
(d) (i), (iii) and (iv)
Ans: (d) (i), (iii) and (iv)
Q70. Which of the following does not have a fixed melting point/boiling point?
(a) gold (b) ethanol (c) air (d) oxygen
Ans: (c) air
🔹 HOTS Questions
Q71. In the following set of substances, one item does not belong to the set. Select this item and explain why it does not belong to the set:
Hydrogen, Oxygen, Steam, Chlorine
Ans:
Steam does not belong to the set because it is a compound (H₂O), while others are elements.
Q72. Iron powder and sulphur powder were mixed and divided into two parts A and B... (full question)
Ans:
(a) B is a mixture
(b) C is a compound (iron sulphide)
(c) Gas D – Hydrogen gas
Gas E – Hydrogen gas
(d) Property of gas D – It burns with a ‘pop’ sound
(e) Test for gas E – Bring a burning matchstick, it produces ‘pop’ sound
🔹 Answers (Q72–75)
Q72. (a) What type of substance is B?
Ans: B is a mixture
Q72. (b) What type of substance is C?
Ans: C is a compound (iron sulphide)
Q72. (c) Name the gas (i) D, and (ii) E?
Ans:
(i) D – Hydrogen gas
(ii) E – Hydrogen gas
Q72. (d) State one characteristic property of gas D.
Ans: It burns with a ‘pop’ sound
Q72. (e) Write one test to identify gas E.
Ans: Bring a burning matchstick near it, it produces a ‘pop’ sound
🔹 Q73
Q73 (a). What type of substance could X be? Name one substance like X.
Ans:
X is a mixture
Example: Air
Q73 (b). What type of substance could Y be? Name one substance like Y.
Ans:
Y is an element
Example: Oxygen
Q73 (c). What type of substance could Z be? Name one substance like Z.
Ans:
Z is a compound
Example: Water
Q73 (d). Which process involves absorption or release of an appreciable amount of energy: formation of X or formation of Z?
Ans: Formation of Z (compound)
Q73 (e). Name the three groups into which all the substances like Y are divided on the basis of their properties.
Ans: Metals, Non-metals, Metalloids
🔹 Q74
Q74 (a). What could the group of materials P be?
Ans: Elements
Q74 (b). Name the substances Q. Give two examples of such substances.
Ans:
Q – Non-metals
Examples: Oxygen, Sulphur
Q74 (c). Name the substances R. Write two examples of such substances.
Ans:
R – Metals
Examples: Iron, Copper
Q74 (d). Name the substances S. Give two examples of such substances.
Ans:
S – Metalloids
Examples: Silicon, Germanium
Q74 (e). Out of Q, R and S, which substances are malleable and ductile?
Ans: R (Metals)
🔹 Q75
Q75 (a). Which liquid could be an element? Name this element.
Ans:
Liquid B – Mercury
Q75 (b). Which liquid could be a mixture? Name this mixture.
Ans:
Liquid A – Petrol
Q75 (c). Which liquid could be a compound? Name this compound.
Ans:
Liquid C – Water
Q75 (d). What could the solid D be?
Ans: Common salt
Q75 (e). What do you think is liquid E?
Ans: Water
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