Physics 9th New Book Chapter 7 Short Questions
Physics 9th New Book Chapter 7 Short Questions solution. 9th Class New Book Chapter 7 Short Questions notes.
Short Answer Questions Physics Class 9 New Book 2025 Chapter 7
Q1 Why solids have a fixed volume and shape according to particle theory of matter?
Solids have fixed volume and shape due to the following reasons.
In solids, particles are tightly packed and there is a very little space between them.
Force between the particles in a solid are very strong.
In solids, particles vibrate about their fixed position but they cannot move from one point to another.
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Q2 What are the reasons that gases have neither a fixed volume nor a fixed shape?
Gases have neither fixed volume nor fixed shape due to the following reasons.
In gases, particles are not tightly packed and there is a large space between them.
Force between the particles in a solid are very weak.
In gases, particles are in constant random and rapid motion.
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Q3 Compare the spacing of molecules in the solid, liquid and gaseous state.
Solids have least molecular spacing. Liquids have more spacing than solids, but less than gases. Gases have the most molecular spacing.
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Q4 What is the effect of raising the temperature of a liquid?
Due to raise in temperature of a liquid molecular motion increases, viscosity decreases, rate of evaporation increases and expansion occurs.
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Q5 What is meant by temperature of a body? Define heat as’ energy in transit.
Temperature of a body is the measurement of the average kinetic energy of the molecules of the that body.
Heat is energy in transit from one body to another because of temperature difference.
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Q6 What is meant by thermometric property of a substance? Enlist some thermometric properties.
Thermometric property is a physical property of a substance that changes with temperature. We can measure thermometric property to determine the temperature of the body. Examples of thermometric properties are volume of a gas at constant pressure, pressure of a gas at constant volume and electrical resistance of a metal.
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Q7 State the main scales used for the measurement of temperature.
We use three main scales for the measurement of temperature. Celsius scale, Fahrenheit scale and Kelvin scale. Other name of Celsius scale is Centigrade scale.
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Q8 What is meant by sensitivity of a thermometer?
Sensitivity of a thermometer means how clearly and quickly a thermometer responds to a small temperature change.
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Q9 What do you mean by linearity of the thermometer?
Linearity of a thermometer means equal changes in temperature produce equal changes in the thermometer reading.
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Q10 What makes the scales reading of a thermometer accurate?
Proper calibration, linearity of thermometric property, quality of thermometric substance, fine and uniform capillary tube, no delay in response and proper marking make the scale reading of thermometer accurate.
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Q11 What does determine the direction of heat flow?
Temperature difference tells us about the direction of heat flow. Heat always flows from hotter object to the colder object because molecules in the hotter object have more kinetic energy and they transfer it.
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Q12 Distinguish between the heat and internal energy.
Heat is energy in transit due to temperature difference. It flows from hot object to clod object. It is denoted by Q.
Internal energy is the total energy of molecules inside a body. It does not flow. It is denoted by U or E.
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Q13 When you touch a cold surface, does cold travel from the surface to your hand or does energy travel from your hand to cold surface?
No, cold does not travel from cold surface. Energy flows from warm hand to cold surface, making the hand feel cold.
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Q14 Can you feel your fever by touching your own forehead? Explain.
No, we cannot feel our own fever by touching our own forehead. This is because hand and forehead are at the same temperature, so there is not heat flow to feel.
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