PHYSICS

 MATTER

PHICAL QUANTITIES AND MEASUREMENT

Basics of Physical Quantities

1. What is a physical quantity?

   • A property of an object that can be measured, like length, mass, or time.

2. What are the two types of physical quantities?

   • Fundamental and derived quantities.

3. What are fundamental quantities?

   • Physical quantities that do not depend on other quantities (e.g., length, mass, time).

4. What are derived quantities?

   • Quantities that are derived from fundamental quantities (e.g., speed, area, volume).

5. How many fundamental quantities are there?

   • Seven.

6. Give two examples of fundamental quantities.

   • Length and mass.

7. Give two examples of derived quantities.

   • Speed and density.

8. What is the SI unit of mass?

   • Kilogram (kg).

9. What is the SI unit of length?

   • Meter (m).

10. What is the SI unit of time?

• Second (s).

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Section 2: Units and Measurement

11. What is measurement?

• The process of comparing a quantity with a standard unit.

12. What is the standard unit of measurement?

• The unit defined by the International System of Units (SI).

13. What is a meter used to measure?

• Length.

14. What is a kilogram used to measure?

• Mass.

15. What is a second used to measure?

• Time.

16. What is a unit?

• A fixed standard quantity used for measurement.

17. What is a standard unit?

• A universally accepted unit of measurement.

18. Name two non-standard units of length.

• Hand span and footstep.

19. Why are standard units needed?

• To ensure accurate and consistent measurements.

20. What are the two types of units?

• Fundamental and derived units.

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Section 3: Measuring Length

21. What instrument is used to measure length?

• A meter scale or measuring tape.

22. What is the SI unit of length?

• Meter (m).

23. What are smaller units of length?

• Centimeter (cm) and millimeter (mm).

24. How many millimeters are in 1 cm?

• 10 mm.

25. How many centimeters are in 1 meter?

• 100 cm.

26. How many meters are in 1 kilometer?

• 1000 m.

27. What is a vernier caliper used for?

• Measuring small lengths accurately.

28. What is a micrometer screw gauge used for?

• Measuring very small thicknesses.

29. What is the approximate length of a human footstep?

• Around 0.8 meters.

30. Why do we avoid using hand span for measurement?

• Because it is not accurate or standard.

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Section 4: Measuring Mass

31. What is mass?

• The amount of matter in an object.

32. What is the SI unit of mass?

• Kilogram (kg).

33. What are smaller units of mass?

• Gram (g) and milligram (mg).

34. How many grams are in 1 kg?

• 1000 g.

35. What instrument is used to measure mass?

• A beam balance or electronic balance.

36. Which is heavier: 1 kg of cotton or 1 kg of iron?

• Both have the same mass, 1 kg.

37. Which is more accurate: a beam balance or an electronic balance?

• An electronic balance.

38. What is the approximate mass of a paperclip?

• Around 1 gram.

39. How many milligrams are in 1 gram?

• 1000 mg.

40. Which has more mass: 1 liter of water or 1 liter of oil?

• Water, because it is denser.

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Section 5: Measuring Time

41. What is time?

• The duration of an event.

42. What is the SI unit of time?

• Second (s).

43. What instrument is used to measure time?

• A stopwatch or clock.

44. How many seconds are in 1 minute?

• 60 seconds.

45. How many minutes are in 1 hour?

• 60 minutes.

46. How many hours are in a day?

• 24 hours.

47. Which is a more accurate time-measuring device: a pendulum clock or a digital watch?

• A digital watch.

48. What is a year?

• The time taken by Earth to complete one orbit around the Sun.

49. What is a leap year?

• A year with 366 days, occurring every four years.

50. What is the smallest unit of time?

• A second.

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Section 6: Measuring Temperature

51. What is temperature?

• The degree of hotness or coldness of an object.

52. What is the SI unit of temperature?

• Kelvin (K).

53. What are two other common units of temperature?

• Celsius (°C) and Fahrenheit (°F).

54. What is the freezing point of water in Celsius?

• 0°C.

55. What is the boiling point of water in Celsius?

• 100°C.

56. What instrument is used to measure temperature?

• A thermometer.

57. What is the normal body temperature in Celsius?

• 37°C.

58. Which is hotter: 40°C or 104°F?

• They are the same temperature.

59. What happens when an object is heated?

• Its temperature increases.

60. Which scale is used in scientific work?

• Kelvin scale.

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Section 7: Miscellaneous Questions

61. Which physical quantity measures the amount of space occupied by an object?

• Volume.

62. What is the SI unit of volume?

• Cubic meter (m³).

63. What is the smaller unit of volume?

• Liter (L).

64. How many milliliters are in 1 liter?

• 1000 mL.

65. What is density?

• Mass per unit volume of a substance.

66. What is the SI unit of density?

• Kilogram per cubic meter (kg/m³).

67. What is speed?

• Distance traveled per unit time.

68. What is the SI unit of speed?

• Meter per second (m/s).

69. What is acceleration?

• The rate of change of speed.

70. What is the SI unit of acceleration?

• Meter per second squared (m/s²).

91. What is the boiling point of water in Fahrenheit?

• 212°F.

92. What is the freezing point of water in Fahrenheit?

• 32°F.

93. Which temperature scale is used in science?

• Kelvin (K).

94. What is absolute zero in Kelvin?

• 0 K (-273.15°C).

95. How is the volume of a cube measured?

• Volume = Side³.

96. What is the volume of a cube with a side length of 2 cm?

• 8 cm³.

97. What is the formula for density?

• Density = Mass / Volume.

98. Why does oil float on water?

• Because oil has a lower density than water.

99. What is the density of water?

• 1 g/cm³ or 1000 kg/m³.

100. Which is denser: iron or wood?

• Iron.

Fill in the Blanks (With Answers)

1. The SI unit of length is the ___ . (meter)

2. A micrometer screw gauge is used to measure ___ objects. (very small)

3. The SI unit of mass is the ___ . (kilogram)

4. One kilometer is equal to ___ meters. (1000)

5. The time taken by the Earth to complete one rotation is ___ hours. (24)

6. The standard unit of time is the ___ . (second)

7. A measuring cylinder is used to measure the ___ of a liquid. (volume)

8. The density of an object is calculated as ___ . (Mass / Volume)

9. A speedometer measures the ___ of a vehicle. (speed)

10. Lubricants are used in machines to ___ friction. (reduce)

11. A pendulum clock measures time in ___ . (seconds)

12. A vernier caliper is used to measure ___ objects. (small)

13. 1 liter is equal to ___ milliliters. (1000)

14. The SI unit of temperature is ___ . (Kelvin)

15. The normal human body temperature is ___ °C. (37)

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True or False (With Answers)

16. The SI unit of mass is gram. (False)

17. A stopwatch measures time accurately. (True)

18. Speed is measured in meters per second (m/s). (True)

19. 1 kilogram is equal to 1000 grams. (True)

20. The density of water is 10 g/cm³. (False)

21. A larger object always has more mass than a smaller object. (False)

22. Volume is measured in square meters. (False)

23. Force can be measured using a spring balance. (True)

24. A liter is a unit of mass. (False)

25. A thermometer is used to measure temperature. (True)

26. Friction always helps in motion. (False)

27. A measuring tape is used to measure long distances. (True)

28. A millimeter is larger than a centimeter. (False)

29. A weighing balance measures the weight of an object. (True)

30. A day has 12 hours. (False)

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10 Math Problems on Physical Quantities and Measurement

Basic Problems

31. A rope is 2.5 meters long. How many centimeters is it?

• Solution: 1 meter = 100 cm

• 2.5 × 100 = 250 cm

• Answer: 250 cm

32. Convert 5 kilograms into grams.

• Solution: 1 kg = 1000 g

• 5 × 1000 = 5000 g

• Answer: 5000 g

33. A car travels 200 km in 4 hours. Find its speed in km/h.

• Solution: Speed = Distance ÷ Time

• 200 ÷ 4 = 50 km/h

• Answer: 50 km/h

34. Find the area of a rectangle with length 5 m and width 3 m.

• Solution: Area = Length × Width

• 5 × 3 = 15 m²

• Answer: 15 m²

35. Find the density of an object with mass 250 g and volume 50 cm³.

• Solution: Density = Mass ÷ Volume

• 250 ÷ 50 = 5 g/cm³

• Answer: 5 g/cm³

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Advanced Problems

36. A person walks 3 km in 30 minutes. Find their speed in m/min.

• Solution: Convert 3 km to meters → 3 × 1000 = 3000 m

• Speed = Distance ÷ Time

• 3000 ÷ 30 = 100 m/min

• Answer: 100 m/min

37. A water tank holds 2.5 liters of water. Convert this into milliliters.

• Solution: 1 liter = 1000 mL

• 2.5 × 1000 = 2500 mL

• Answer: 2500 mL

38. A clock gains 5 minutes every hour. How many extra minutes will it gain in 24 hours?

• Solution: 5 min × 24 = 120 min

• Answer: 120 minutes or 2 hours

39. A cube has sides of 4 cm. Find its volume.

• Solution: Volume = Side³

• 4 × 4 × 4 = 64 cm³

• Answer: 64 cm³

40. A train moves 90 km in 1.5 hours. Find its speed in m/s.

• Solution: Convert 90 km to meters → 90 × 1000 = 90000 m

• Convert 1.5 hours to seconds → 1.5 × 3600 = 5400 s

• Speed = 90000 ÷ 5400 = 16.67 m/s

• Answer: 16.67 m/s

FORCE

ENERGY

LIGHT

MAGNETISM

FORCE

: Force and Its Types

1. What is force?

   • Force is a push or a pull that changes the state of motion or shape of an object.

2. What are the two main types of force?

   • Contact force and Non-contact force.

3. Give two examples of contact force.

   • Pushing a door, kicking a football.

4. Give two examples of non-contact force.

   • Gravitational force, Magnetic force.

5. What is a push force?

   • A force applied to move an object away.

6. What is a pull force?

   • A force applied to bring an object closer.

7. What happens when force is applied to a stationary object?

   • It can start moving.

8. What happens when force is applied to a moving object?

   • It can stop, change speed, or change direction.

9. How does force affect the shape of an object?

   • It can change the shape, like squeezing a rubber ball.

10. What is muscular force?

• The force exerted by our muscles, like lifting a bag.

11. What is gravitational force?

• The force by which the Earth pulls everything towards itself.

12. Who discovered the force of gravity?

• Sir Isaac Newton.

13. What is magnetic force?

• The force exerted by a magnet on magnetic materials like iron.

14. Give an example of magnetic force.

• A magnet attracting iron nails.

15. What is electrostatic force?

• The force exerted by charged objects, like rubbing a balloon on hair.

16. What is normal force?

• The support force exerted by a surface, like a table holding a book.

17. What is tension force?

• The force transmitted through a string, rope, or wire when pulled tight.

18. What is air resistance?

• A force that slows down objects moving through air, like a parachute.

19. What is water resistance?

• A force that slows down objects moving through water, like a boat.

20. What is spring force?

• The force exerted by a stretched or compressed spring.

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Section 2: Friction and Its Effects

21. What is friction?

• A force that opposes motion between two surfaces in contact.

22. Give an example of friction.

• Rubbing hands together to produce heat.

23. What are the effects of friction?

• It can slow down or stop motion and produce heat.

24. Name the four types of friction.

• Static friction, Sliding friction, Rolling friction, and Fluid friction.

25. What is static friction?

• The friction that prevents an object from moving.

26. What is sliding friction?

• The friction that occurs when an object slides over a surface.

27. What is rolling friction?

• The friction that occurs when an object rolls over a surface.

28. What is fluid friction?

• The friction between objects and liquids or gases.

29. Which type of friction is the strongest?

• Static friction.

30. Which type of friction is the weakest?

• Rolling friction.

31. Why do we put oil in machines?

• To reduce friction.

32. Why do we use ball bearings in machines?

• To convert sliding friction into rolling friction.

33. Why do athletes wear special shoes?

• To increase friction and prevent slipping.

34. Why does a car stop when brakes are applied?

• Due to friction between the tires and the road.

35. What happens if there is no friction?

• We would not be able to walk, write, or hold objects.

36. Why do we use sand on icy roads?

• To increase friction and prevent slipping.

37. Why do we apply grease to bicycle chains?

• To reduce friction and make movement smoother.

38. Why do rough surfaces create more friction?

• Because they have more irregularities that interlock.

39. Why does a ball stop rolling after some time?

• Due to friction between the ball and the ground.

40. How does friction help in writing?

• It prevents the pen from slipping.

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Section 3: Advantages and Disadvantages of Friction

41. What are the advantages of friction?

• Helps in walking, writing, driving, and holding objects.

42. What are the disadvantages of friction?

• Causes wear and tear, produces heat, wastes energy.

43. Why do tyres have grooves?

• To increase friction and prevent skidding.

44. Why do car engines get hot?

• Due to friction between moving parts.

45. Why do erasers work?

• Friction removes pencil marks from paper.

46. What happens if there is too much friction?

• It can damage objects and make movement difficult.

47. Why is it difficult to walk on a wet floor?

• Water reduces friction, making the surface slippery.

48. Why do we use powder on carrom boards?

• To reduce friction and allow smooth movement of coins.

49. Why do we use lubricants in machines?

• To reduce friction and prevent wear and tear.

50. Why does a parachute slow down a falling person?

• Due to air resistance.

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Section 4: Ways to Reduce and Increase Friction

51. How can friction be reduced?

• By using lubricants, polishing surfaces, using ball bearings.

52. Why do aeroplanes have smooth surfaces?

• To reduce air resistance and move faster.

53. What is the role of oil in door hinges?

• It reduces friction, allowing smooth movement.

54. Why do we use wax on skis?

• To reduce friction and glide smoothly.

55. How can friction be increased?

• By making surfaces rough, increasing weight, using treads.

56. Why do mountaineers wear spiked shoes?

• To increase friction and prevent slipping.

57. Why do tyres have deep treads?

• To increase friction for better grip on the road.

58. What is the advantage of rough soles in shoes?

• Provides more friction and prevents slipping.

59. Why do roads have speed breakers?

• To increase friction and reduce speed.

60. What happens when bicycle brakes are applied?

• Friction between brake pads and wheels slows down the cycle.

61. What is the SI unit of force?

• Newton (N).

62. Who gave the laws of motion?

• Sir Isaac Newton.

63. What happens when two equal and opposite forces act on an object?

• The object remains stationary or in uniform motion.

64. What is a balanced force?

• When two forces cancel each other, causing no motion.

65. What is an unbalanced force?

• When one force is stronger, causing motion in one direction.

66. Give an example of an unbalanced force.

• Kicking a football.

67. How does force affect motion?

• It can start, stop, speed up, slow down, or change direction.

68. Which force keeps planets in orbit around the Sun?

• Gravitational force.

69. What is elastic force?

• The force exerted by a stretched or compressed object, like a rubber band.

70. Give an example of elastic force.

• A stretched slingshot.

71. What is the force exerted by liquids called?

• Buoyant force.

72. Why do boats float on water?

• Due to buoyant force.

73. Which force helps birds and airplanes fly?

• Lift force.

74. Which force acts against motion in air?

• Air resistance.

75. Which force is responsible for tides in the ocean?

• Gravitational force of the Moon and Sun.

76. What is the direction of gravitational force?

• Always towards the center of the Earth.

77. What is force exerted by a surface called?

• Normal force.

78. What happens when you push a book on a table?

• It moves due to applied force but slows due to friction.

79. Why do parachutes help in landing?

• They increase air resistance and slow down motion.

80. How do rockets overcome Earth's gravity?

• By applying a strong thrust force.

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Section 6: More Questions on Friction

81. Why does friction produce heat?

• Because it resists motion, converting energy into heat.

82. Why do tires wear out over time?

• Due to continuous friction with the road.

83. Which is greater: sliding friction or rolling friction?

• Sliding friction.

84. Why do ice skaters glide smoothly?

• Because ice has very low friction.

85. Why do astronauts float in space?

• Due to the absence of gravity and friction.

86. What happens when friction is removed completely?

• Objects will keep moving without stopping.

87. Why do we use chalk powder in gymnastics?

• To increase friction for a better grip.

88. Why do new shoes slip on smooth surfaces?

• Because they have less friction.

89. Why do car engines need cooling systems?

• To remove heat generated by friction.

90. Which friction is useful in writing on a blackboard?

• Static friction between chalk and board.

91. What will happen if brakes fail in a car?

• The car will not stop because friction is not applied.

92. Which friction is useful in gripping a pen?

• Static friction.

93. Why do trucks have larger tires?

• To increase friction for better control.

94. Which type of friction helps in walking?

• Static friction.

95. Why do matchsticks light up when rubbed?

• Due to heat generated by friction.

96. What is streamlined shape?

• A shape that reduces fluid friction, like a fish or an airplane.

97. How does a lubricated surface affect friction?

• It decreases friction.

98. Which force slows down a bicycle?

• Friction.

99. Why do aeroplanes have pointed noses?

• To reduce air resistance.

100. How does friction help in daily life?

 More Questions on Force

101. What is meant by the magnitude of force?

• The strength or amount of force applied.

102. What happens when two unequal forces act in opposite directions?

• The object moves in the direction of the larger force.

103. Why does a ball bounce back after hitting the ground?

• Due to the reaction force from the ground.

104. What is the unit of mass?

• Kilogram (kg).

105. How is mass different from weight?

• Mass is the amount of matter in an object, while weight is the force due to gravity.

106. What will happen to an object in space if no force acts on it?

• It will continue moving in the same direction forever.

107. Why do some objects float on water while others sink?

• Due to the balance between gravitational and buoyant forces.

108. Why do we feel lighter in water?

• Because of the upward buoyant force.

109. How does a jet engine work?

• It pushes air backward to create a forward force (thrust).

110. What force is responsible for a stretched rubber band returning to its original shape?

• Elastic force.

111. Why does a spaceship move forward in space when fired?

• Due to the reaction force from the expelled gas (Newton’s Third Law).

112. What happens when we jump?

• We apply a downward force on the ground, and the ground applies an upward reaction force.

113. How does a hovercraft reduce friction?

• By floating on a cushion of air.

114. Why do speedboats have a special shape?

• To reduce water resistance and move faster.

115. How do astronauts move in space without gravity?

• By pushing against objects to create a reaction force.

116. Why do bicycles move faster when we stop pedaling downhill?

• Due to the force of gravity pulling it downward.

117. Which force is used in a bow and arrow?

• Elastic force from the stretched bowstring.

118. What is a reaction force?

• The force exerted in response to an applied force (Newton’s Third Law).

119. Why do doors have handles far from the hinges?

• To apply less force to open the door easily.

120. Which force pulls us toward the Earth?

• Gravitational force.

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Section 8: More Questions on Friction

121. Why do rough surfaces create more friction?

• Because they have more irregularities that interlock.

122. Why do objects stop moving after some time?

• Due to friction acting against motion.

123. Why is it difficult to drag a heavy box on the floor?

• Due to high friction between the box and the floor.

124. What is the advantage of rolling friction over sliding friction?

• Rolling friction is much smaller, making movement easier.

125. What happens when a moving car suddenly stops?

• Due to friction, the car stops, but passengers move forward due to inertia.

126. Why do ball bearings reduce friction?

• They change sliding friction into rolling friction, which is weaker.

127. Why do trains have smooth wheels?

• To reduce friction with the railway tracks.

128. Why do vehicles slip on wet roads?

• Water reduces friction between tires and the road.

129. Why do birds have streamlined bodies?

• To reduce air resistance and fly easily.

130. Why do ships have pointed fronts?

• To reduce water resistance.

131. Why do bats and aeroplanes have similar wing shapes?

• To reduce air friction and fly efficiently.

132. What happens when oil is spilled on the floor?

• The surface becomes slippery due to reduced friction.

133. Why do new shoes have rough soles?

• To increase friction for better grip.

134. How does friction help in holding objects?

• It prevents objects from slipping out of our hands.

135. Why does a ball thrown on a smooth floor travel farther than on a rough floor?

• Because there is less friction on the smooth floor.

136. What happens when we rub our palms together?

• Friction generates heat, making our palms warm.

137. Why does a rocket move faster in space than on Earth?

• There is no air resistance or friction in space.

138. Why do sports cars have wide tires?

• To increase friction and improve grip on the road.

139. Why do vehicles slow down on sandy roads?

• Sand increases friction, making movement harder.

140. Why do swimmers wear tight swimsuits?

• To reduce water resistance and swim faster.

141. Why do cyclists bend forward while racing?

• To reduce air resistance and increase speed.

142. How does a roller coaster slow down?

• Due to friction between the tracks and wheels.

143. Why is it difficult to walk on ice?

• Ice has very low friction, making it slippery.

144. Why do plane wheels have grooves like car tires?

• To increase friction during landing.

145. How does a plane land safely despite its speed?

• Brakes and air resistance help reduce speed.

146. Why does a rope burn our hand if pulled too fast?

• Due to heat generated by friction.

147. Why do machines wear out over time?

• Because friction causes parts to wear down.

148. Why do marathon runners prefer dry socks?

• Wet socks reduce friction and cause blisters.

149. Why do elephants have large feet?

• To increase friction and prevent sinking into soft ground.

150. Why does a rough road slow down a bicycle?

• Because rough surfaces create more friction.

True or False

1. Force can only be a push, not a pull. (False)

2. Gravity is a contact force. (False)

3. A magnet can attract all types of metals. (False)

4. Friction always acts in the direction of motion. (False)

5. Lubricants reduce friction. (True)

6. Friction is necessary for walking. (True)

7. Sliding friction is greater than rolling friction. (True)

8. The force applied by our hands is called muscular force. (True)

9. Without friction, we would not be able to write with a pencil. (True)

10. Air resistance is a type of friction. (True)

11. Friction can cause wear and tear of machines. (True)

12. A car moving on a road experiences no friction. (False)

13. Ball bearings reduce friction. (True)

14. A smooth surface creates more friction than a rough surface. (False)

15. A force can change the shape of an object. (True)

16. The gravitational force of the Moon is stronger than that of the Earth. (False)

17. Weight and mass are the same. (False)

18. We apply brakes in a vehicle to increase friction. (True)

19. Water reduces friction between objects. (True)

20. Rough shoes increase friction and prevent slipping. (True)

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Fill in the Blanks

21. Force is a ___ or a ___. (push, pull)

22. The force exerted by the Earth on objects is called ___. (gravity)

23. The force that resists motion is called ___. (friction)

24. The SI unit of force is ___. (Newton)

25. Friction produces ___. (heat)

26. ___ force is responsible for keeping planets in orbit. (Gravitational)

27. Friction is caused by the ___ between two surfaces. (irregularities)

28. Rolling friction is ___ than sliding friction. (less)

29. A parachute slows down due to ___. (air resistance)

30. Oil and grease are used in machines to ___ friction. (reduce)

31. We use rough soles in shoes to ___ friction. (increase)

32. Lubricants such as ___ help in reducing friction. (oil/grease)

33. Magnetic force is a ___ force. (non-contact)

34. A smooth surface has ___ friction than a rough surface. (less)

35. A moving car stops due to ___. (friction)

36. Sliding friction is ___ than static friction. (less)

37. The shape of an airplane is designed to reduce ___. (air resistance)

38. A rolling object experiences ___ friction. (rolling)

39. When we press a sponge, its ___ changes. (shape)

40. The force that acts in liquids and gases is called ___ friction. (fluid)

41. A heavy box is harder to move due to ___ friction. (static)

42. Speed breakers on roads ___ friction to slow down vehicles. (increase)

43. Athletes wear spiked shoes to ___ friction. (increase)

44. ___ friction helps us to hold objects in our hands. (Static)

45. Friction is both useful and ___. (harmful)

46. A bicycle moves forward when we pedal due to applied ___. (force)

47. The force that prevents slipping on roads is ___. (friction)

48. In space, astronauts float because there is no ___. (gravity)

49. A matchstick lights up because of heat produced by ___. (friction)

50. Machines wear out over time because of ___. (friction)

MATTER

1,Definition of Matter
Matter is anything that has mass and occupies space (volume). It is composed of tiny particles, such as atoms and molecules, which are the fundamental building blocks of all physical substances.
Composition of Matter
Matter is primarily composed of:

Atoms – The smallest unit of an element, consisting of:

Protons (positively charged)
Neutrons (neutral)
Electrons (negatively charged)

Distinguishing Between Solid, Liquid, and Gas

Matter exists in three primary states: Solid, Liquid, and Gas. These states differ in terms of shape, volume, molecular arrangement, and movement.

Property	Solid	Liquid	Gas
Shape	Fixed	Takes the shape of the container	No fixed shape, fills the entire container
Volume	Fixed	Fixed, but can change shape	No fixed volume, expands to fill the container
Molecular Arrangement	Tightly packed in a fixed pattern	Loosely packed, can move around each other	Very loosely arranged, move freely
Molecular Movement	Vibrate in fixed positions	Move and slide past each other	Move randomly at high speed
Compressibility	Almost incompressible	Slightly compressible	Highly compressible
Flow Ability	Cannot flow	Can flow easily	Flows in all directions
Examples	Ice, wood, metal	Water, oil, milk	Oxygen, steam, carbon dioxide

• 
  

Molecules – Formed when two or more atoms bond together.
Subatomic Particles – Protons, neutrons, and electrons are further made up of even smaller particles like quarks and leptons.
Classification of Matter
Matter can be classified into:
Pure Substances (Elements & Compounds)
Mixtures (Homogeneous & Heterogeneous)

Q1,Name the three states of matter.

• The three primary states of matter are:

  1. Solid – Has a definite shape and volume (e.g., ice, wood).

  2. Liquid – Has a definite volume but takes the shape of its container (e.g., water, milk).

  3. Gas – Has neither a definite shape nor a definite volume (e.g., oxygen, steam).

  There are also other states, like plasma and Bose-Einstein condensate (BEC), but these are less common in everyday life. 

Q,3What is a molecule ?

Definition of a Molecule
A molecule is the smallest unit of a substance that retains its chemical properties and is composed of two or more atoms bonded together. These atoms can be of the same element or different elements.
Types of Molecules
Molecules of Elements – Made of the same type of atoms.
Example: O₂ (Oxygen), N₂ (Nitrogen)
Molecules of Compounds – Made of different types of atoms.
Example: H₂O (Water), CO₂ (Carbon dioxide)

Molecules are held together by chemical bonds, such as covalent bonds. 

Mention one example each of a monoatomic and a diatomic molecule.

• Monoatomic Molecule: Helium (He) – A noble gas that exists as single atoms.

• Diatomic Molecule: Oxygen (O₂) – Consists of two oxygen atoms bonded together.

Q,5,What do you mean by inter-molecular spacing?

Inter-Molecular Spacing

Inter-molecular spacing refers to the distance between the molecules of a substance. It determines the state of matter and how particles interact with each other.

Inter-Molecular Spacing in Different States of Matter

1. Solids – Very small inter-molecular spacing (molecules are tightly packed).

2. Liquids – Moderate inter-molecular spacing (molecules are loosely packed).

3. Gases – Large inter-molecular spacing (molecules are far apart and move freely).

This spacing affects properties like density, compressibility, and fluidity. 

Q6What do you mean by inter-molecular forces ? 

Inter-Molecular Forces

Inter-molecular forces are the forces of attraction or repulsion between molecules. These forces determine the physical state, boiling point, and melting point of a substance.

Types of Inter-Molecular Forces

1. Dipole-Dipole Forces – Between polar molecules (e.g., HCl).

2. Hydrogen Bonding – Strong force in molecules with H bonded to N, O, or F (e.g., H₂O).

3. London Dispersion Forces – Weak forces in all molecules, especially nonpolar ones (e.g., O₂, CO₂).

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❓ Q1: What is the role of inter-molecular forces in determining the state of matter?
✅ A1: Stronger inter-molecular forces hold molecules closer, making a substance solid or liquid. Weaker forces allow molecules to move freely, making it a gas.

❓ Q2: Which inter-molecular force is the strongest?
✅ A2: Hydrogen bonding is the strongest among inter-molecular forces.

❓ Q3: Why do gases have weak inter-molecular forces?
✅ A3: In gases, molecules are far apart, so the inter-molecular forces are very weak, allowing free movement.

Q7,What are the forces of cohesion and adhesion ?

Forces of Cohesion and Adhesion

1. Cohesion: The force of attraction between molecules of the same substance.

   • Example: Water molecules sticking together, forming droplets.

   • This force is responsible for surface tension in liquids.

2. Adhesion: The force of attraction between molecules of different substances.

   • Example: Water sticking to a glass surface.

   • This force helps in capillary action, like water rising in plant roots.

Would you like a comparison table for better understanding? 😊

Three Characteristics of Molecules That Determine the State of Matter

1. Inter-Molecular Spacing

   • Solid: Very small (molecules are tightly packed).

   • Liquid: Moderate (molecules are loosely packed).

   • Gas: Large (molecules are far apart).

2. Inter-Molecular Forces

   • Solid: Strong (holds molecules in fixed positions).

   • Liquid: Moderate (allows flow but keeps molecules close).

   • Gas: Weak (molecules move freely in all directions).

3. Molecular Motion (Kinetic Energy)

   • Solid: Very low (molecules vibrate in place).

   • Liquid: Moderate (molecules slide past each other).

   • Gas: High (molecules move rapidly and randomly).

Would you like a table format for easy comparison? 

The molecules in a substance are in motion. What type of path do they follow ?

The molecules in a substance move in a random and irregular manner. The type of path they follow depends on the state of matter:

1. In Solids – Molecules vibrate back and forth around fixed positions.

2. In Liquids – Molecules move in a zig-zag manner, sliding past each other.

3. In Gases – Molecules move in a random, straight-line motion until they collide with other molecules or the container walls. This motion is called Brownian motion.

Would you like an illustration or a more detailed explanation? 😊

0. Complete the following: (a) Solid Liquid (b) Boiling Gas

Here are the completed answers:

(a) Solid → Liquid → Gas (This represents the states of matter transition: Melting and Evaporation)

(b) Boiling → Gas → Condensation (Boiling converts a liquid into a gas, and condensation changes gas back into a liquid)

Distinguishing Between Solid, Liquid, and Gas

Matter exists in three primary states: Solid, Liquid, and Gas. These states differ in terms of shape, volume, molecular arrangement, and movement.

Property	Solid	Liquid	Gas
Shape	Fixed	Takes the shape of the container	No fixed shape, fills the entire container
Volume	Fixed	Fixed, but can change shape	No fixed volume, expands to fill the container
Molecular Arrangement	Tightly packed in a fixed pattern	Loosely packed, can move around each other	Very loosely arranged, move freely
Molecular Movement	Vibrate in fixed positions	Move and slide past each other	Move randomly at high speed
Compressibility	Almost incompressible	Slightly compressible	Highly compressible
Flow Ability	Cannot flow	Can flow easily	Flows in all directions
Examples	Ice, wood, metal	Water, oil, milk	Oxygen, steam, carbon dioxide

Properties of Solids, Liquids, and Gases

The three states of matter—solid, liquid, and gas—differ in their physical properties due to the arrangement and movement of particles.

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1. Properties of Solids

• Definite Shape: Solids have a fixed shape and do not change unless force is applied.

• Definite Volume: They occupy a fixed amount of space and do not expand or contract easily.

• Rigid and Hard: Most solids are hard and difficult to compress.

• Particles are Tightly Packed: The molecules are closely arranged in a fixed pattern.

• Least Molecular Movement: The particles only vibrate in place but do not move freely.

• Incompressible: Solids cannot be compressed easily.

• Does Not Flow: Solids do not take the shape of a container.

👉 Examples: Wood, ice, iron, stone

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2. Properties of Liquids

• No Fixed Shape: Liquids take the shape of the container they are placed in.

• Definite Volume: They have a fixed volume but no fixed shape.

• Less Dense than Solids: The particles are loosely arranged and can move around.

• Flow Easily: Liquids can flow from one place to another.

• Slightly Compressible: They can be compressed slightly under pressure.

• Surface Tension: Liquids form droplets due to cohesive forces between molecules.

👉 Examples: Water, milk, oil, juice

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3. Properties of Gases

• No Fixed Shape: Gases take the shape of the container they are in.

• No Fixed Volume: They expand to fill the entire available space.

• Highly Compressible: Gases can be compressed into a smaller volume.

• Low Density: The particles are far apart and move freely.

• Moves Randomly: Gas molecules move in all directions at high speed.

• Can Diffuse Easily: Gases spread and mix with other gases quickly.

👉 Examples: Oxygen, carbon dioxide, nitrogen, steam

List of Solids, Liquids, and Gases

1. Examples of Solids

• Ice

• Wood

• Iron

• Stone

• Brick

• Plastic

• Glass

• Rubber

• Paper

• Gold

2. Examples of Liquids

• Water

• Milk

• Oil

• Honey

• Juice

• Alcohol

• Vinegar

• Mercury (the only metal that is liquid at room temperature)

• Petrol

• Liquid soap

3. Examples of Gases

• Oxygen (O₂)

• Carbon dioxide (CO₂)

• Nitrogen (N₂)

• Hydrogen (H₂)

• Steam (Water vapor)

• Methane (CH₄)

• Helium (He)

• Argon (Ar)

• Chlorine (Cl₂)

• Ozone (O₃)

MCQs on Changes in the State of Matter

1. What is the process of changing a solid into a liquid called?

a) Freezing
b) Condensation
c) Melting
d) Sublimation
(Answer: c) Melting

2. The change of a liquid into a gas is known as:

a) Evaporation
b) Condensation
c) Freezing
d) Deposition
(Answer: a) Evaporation

3. When a gas changes into a liquid, it is called:

a) Freezing
b) Condensation
c) Boiling
d) Melting
(Answer: b) Condensation

4. What is the process where a solid changes directly into a gas?

a) Sublimation
b) Deposition
c) Freezing
d) Boiling
(Answer: a) Sublimation

5. The process of water changing into ice is called:

a) Melting
b) Freezing
c) Evaporation
d) Boiling
(Answer: b) Freezing

6. Dry ice undergoes which process?

a) Melting
b) Freezing
c) Sublimation
d) Boiling
(Answer: c) Sublimation

7. Which of the following causes a solid to melt?

a) Increasing temperature
b) Decreasing temperature
c) Increasing pressure
d) Removing energy
(Answer: a) Increasing temperature

8. What happens to the molecules of a substance when it changes from solid to liquid?

a) They move closer together
b) They stop moving
c) They move farther apart and gain energy
d) They change into atoms
(Answer: c) They move farther apart and gain energy

9. What happens when a gas is compressed?

a) It expands
b) It turns into a liquid
c) Its particles move closer together
d) It disappears
(Answer: c) Its particles move closer together

10. When water boils, it changes into:

a) Ice
b) Vapor
c) Liquid
d) Solid
(Answer: b) Vapor

11. Which of the following is an example of condensation?

a) Water vapor turning into clouds
b) Ice melting into water
c) Water boiling
d) Water freezing into ice
(Answer: a) Water vapor turning into clouds

12. What process occurs when frost forms on a window?

a) Melting
b) Freezing
c) Deposition
d) Evaporation
(Answer: c) Deposition

13. Boiling and evaporation are similar because:

a) Both involve a change from liquid to gas
b) Both occur at the same temperature
c) Both require condensation
d) Both turn into solids
(Answer: a) Both involve a change from liquid to gas

14. What happens to the temperature during melting?

a) It decreases
b) It increases
c) It remains the same
d) It depends on pressure
(Answer: b) It increases

15. Which state of matter has the highest energy?

a) Solid
b) Liquid
c) Gas
d) Plasma
(Answer: d) Plasma

16. Which of the following substances can undergo sublimation?

a) Water
b) Dry ice
c) Milk
d) Iron
(Answer: b) Dry ice

17. What factor influences the rate of evaporation?

a) Temperature
b) Surface area
c) Humidity
d) All of the above
(Answer: d) All of the above

18. What happens to the energy of particles when condensation occurs?

a) Energy increases
b) Energy remains constant
c) Energy decreases
d) Particles disappear
(Answer: c) Energy decreases

19. When you freeze water, the molecules:

a) Gain energy and spread apart
b) Lose energy and come closer
c) Stop moving completely
d) Expand and turn into vapor
(Answer: b) Lose energy and come closer

20. The temperature at which a liquid turns into a gas is called:

a) Freezing point
b) Melting point
c) Boiling point
d) Condensation point
(Answer: c) Boiling point

Intermolecular Forces are Strongest in:

Intermolecular forces are the forces of attraction between molecules. Their strength varies depending on the state of matter and the type of substance.

🔹 Intermolecular forces are strongest in → Solids
🔹 Intermolecular forces are weakest in → Gases

Intermolecular Forces in Liquids

In liquids, intermolecular forces are moderate—stronger than in gases but weaker than in solids. These forces allow liquids to flow while maintaining a definite volume.

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Types of Intermolecular Forces in Liquids

1️⃣ Dipole-Dipole Forces

• Occur in polar molecules (molecules with partial positive and negative charges).

• Example: Water (H₂O), Hydrogen Chloride (HCl)

2️⃣ Hydrogen Bonding (Strongest in liquids)

• Special type of dipole-dipole force where hydrogen is bonded to N, O, or F.

• Example: Water (H₂O), Alcohol (CH₃OH), Ammonia (NH₃)

3️⃣ London Dispersion Forces (Van der Waals Forces)

• Present in all molecules but dominant in nonpolar liquids.

• Weak temporary forces due to electron movement.

• Example: Liquid Oxygen (O₂), Liquid Nitrogen (N₂)

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Effects of Intermolecular Forces in Liquids

🔹 Surface Tension – Liquids with strong intermolecular forces (like water) form droplets.
🔹 Viscosity – Liquids with stronger forces flow slowly (e.g., honey is more viscous than water).
🔹 Boiling Point – Stronger forces mean a higher boiling point (e.g., water boils at 100°C).

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Strength of Intermolecular Forces in Different States of Matter

State of Matter	Intermolecular Force Strength	Molecular Arrangement
Solids	Strongest	Molecules are tightly packed
Liquids	Medium	Molecules are loosely packed
Gases	Weakest	Molecules are far apart and move freely

The diameter of molecules varies depending on the type of molecule. It is usually measured in nanometers (nm) or angstroms (Å), where:

• 1 nanometer (nm) = 10⁻⁹ meters

• 1 angstrom (Å) = 10⁻¹⁰ meters

Approximate Diameters of Some Common Molecules

Molecule	Diameter (nm)	Diameter (Å)
Water (H₂O)	0.275 nm	2.75 Å
Oxygen (O₂)	0.3 nm	3 Å
Nitrogen (N₂)	0.32 nm	3.2 Å
Carbon Dioxide (CO₂)	0.33 nm	3.3 Å
Glucose (C₆H₁₂O₆)	0.9 nm	9 Å
DNA Helix Width	2 nm	20 Å
Sodium Ion (Na⁺)	0.095 nm	0.95 Å
Protein Molecule1-10 n	m	10-100 Å