Quick Review Flashcards - Click to flip and test your knowledge!
Question
How is 'calorimetry' defined?
Answer
It is the measurement of the quantity of heat energy.
Question
What is 'thermal energy'?
Answer
It is the sum of the potential energy and kinetic energy of all the molecules in a substance.
Question
Define 'heat' in terms of energy flow.
Answer
Heat is the form of energy that flows from a hot body to a cold body when they are kept in contact.
Question
What is the S.I. unit of heat?
Answer
The S.I. unit is the joule (symbol J).
Question
Define the 'calorie' as a unit of heat.
Answer
It is the quantity of heat energy required to raise the temperature of $1\text{ g}$ of water through $1^\circ\text{C}$.
Question
To what temperature range does the precise definition of a calorie ($15^\circ\text{C}$ calorie) refer?
Answer
$14.5^\circ\text{C}$ to $15.5^\circ\text{C}$.
Question
What is the numerical relationship between $1\text{ calorie}$ and joules?
Answer
$1\text{ calorie} = 4.186\text{ J}$ (or nearly $4.2\text{ J}$).
Question
How many joules are approximately in $1\text{ kilo-calorie}$?
Answer
$4200\text{ J}$ (nearly).
Question
In thermal physics, what parameter determines the direction of heat flow between two bodies in contact?
Answer
Temperature.
Question
What is the S.I. unit of temperature?
Answer
The S.I. unit is the kelvin (symbol K).
Question
What is the formula to convert temperature in degrees Celsius ($t^\circ\text{C}$) to kelvin ($T$)?
Answer
$T\text{ K} = 273 + t^\circ\text{C}$.
Question
At what temperature does molecular motion cease, known as absolute zero?
Answer
$0\text{ K}$ or $-273^\circ\text{C}$.
Question
How does a temperature difference of $1^\circ\text{C}$ compare to a difference of $1\text{ K}$?
Answer
They are exactly the same ($1^\circ\text{C} = 1\text{ K}$).
Question
List the three factors that determine the quantity of heat energy absorbed by a body.
Answer
Mass of the body, increase in temperature, and the material of the body.
Question
What is the mathematical expression for heat energy ($Q$) absorbed by a body?
Answer
$Q = m c \Delta t$.
Question
What does the constant '$c$' represent in the equation $Q = m c \Delta t$?
Answer
The specific heat capacity of the substance.
Question
How is 'heat capacity' ($C'$) defined?
Answer
It is the amount of heat energy required to raise the temperature of a body by $1^\circ\text{C}$ (or $1\text{ K}$).
Question
What is the S.I. unit of heat capacity ($C'$)?
Answer
The S.I. unit is joule per kelvin ($\text{J K}^{-1}$).
Question
Define 'specific heat capacity'.
Answer
It is the amount of heat energy required to raise the temperature of unit mass of a substance through $1^\circ\text{C}$ (or $1\text{ K}$).
Question
What is the S.I. unit of specific heat capacity?
Answer
The S.I. unit is joule per kilogram per kelvin ($\text{J kg}^{-1}\text{ K}^{-1}$).
Question
How are heat capacity ($C'$) and specific heat capacity ($c$) related mathematically?
Answer
$C' = m \times c$.
Question
Which physical quantity depends on the mass of the body: heat capacity or specific heat capacity?
Answer
Heat capacity ($C'$).
Question
What is the approximate specific heat capacity of water in S.I. units?
Answer
$4200\text{ J kg}^{-1}\text{ K}^{-1}$ (or $4180\text{ J kg}^{-1}\text{ K}^{-1}$).
Question
Substance A is a good conductor of heat; will it typically have a high or low specific heat capacity?
Answer
It will have a low specific heat capacity.
Question
Why is the vessel of a calorimeter typically made of thin copper?
Answer
Copper is a good conductor with low specific heat capacity, ensuring it quickly reaches the contents' temperature with minimal heat absorption.
Question
State the Principle of Method of Mixtures (Principle of Calorimetry).
Answer
In an insulated system, heat energy lost by the hot body is equal to heat energy gained by the cold body.
Question
Upon what fundamental law is the principle of calorimetry based?
Answer
The law of conservation of energy.
Question
Why does the climate near the sea shore remain moderate compared to inland areas?
Answer
Water's high specific heat capacity means it heats up and cools down much more slowly than land.
Question
Explain why water is used as an effective coolant in car radiators.
Answer
It can extract a large amount of heat energy from surroundings without a significant rise in its own temperature due to its high specific heat capacity.
Question
Why do farmers fill their fields with water to protect crops on cold winter nights?
Answer
Water has a high specific heat capacity and does not allow the temperature of the surrounding area to fall below $0^\circ\text{C}$ easily.
Question
Why is the base of a cooking pan made thick and heavy?
Answer
A thick base has a large heat capacity, allowing it to heat slowly and keep food warm for longer.
Question
Define 'change of phase' (state).
Answer
The process of change from one state to another at a constant temperature by the exchange of heat.
Question
What is the term for the change from solid phase to liquid phase at a constant temperature?
Answer
Melting.
Question
Define the 'melting point' of a substance.
Answer
It is the constant temperature at which a solid changes into a liquid.
Question
How is 'vaporisation' defined?
Answer
The change from liquid phase to gas (or vapour) phase upon absorption of heat at a constant temperature.
Question
What is 'latent heat'?
Answer
Heat energy absorbed or liberated during a change of phase that does not result in a change in temperature.
Question
What is 'specific latent heat' ($L$)?
Answer
The quantity of heat energy absorbed or liberated by unit mass of a substance for a change in its phase at a constant temperature.
Question
What is the S.I. unit of specific latent heat?
Answer
Joule per kilogram ($\text{J kg}^{-1}$).
Question
Define 'specific latent heat of fusion of ice'.
Answer
The heat energy required to melt unit mass of ice at $0^\circ\text{C}$ to water at $0^\circ\text{C}$ without a change in temperature.
Question
What is the value of the specific latent heat of fusion of ice in S.I. units?
Answer
$336000\text{ J kg}^{-1}$ (or $336 \times 10^3\text{ J kg}^{-1}$).
Question
According to the kinetic model, what happens to the average kinetic energy of molecules during melting?
Answer
It does not change.
Question
In the kinetic model, for what is the heat energy supplied during melting used?
Answer
It is used to increase the potential energy of the molecules by increasing their separation against attractive forces.
Question
Why does snow on mountains not melt all at once?
Answer
Ice has a high specific latent heat of fusion ($336000\text{ J kg}^{-1}$), requiring a massive amount of heat from the sun to melt.
Question
Why do drinks cool more effectively with $1\text{ g}$ of ice at $0^\circ\text{C}$ than with $1\text{ g}$ of water at $0^\circ\text{C}$?
Answer
The ice absorbs an additional $336\text{ J}$ of heat energy per gram just to melt.
Question
Why is it generally more cold after a hail-storm than during the storm itself?
Answer
Ice starts absorbing a large amount of heat energy from the surroundings to melt, causing the atmospheric temperature to fall.
Question
How does the melting point of ice change with an increase in pressure?
Answer
The melting point decreases with an increase in pressure.
Question
What effect does the addition of impurities have on the melting point of ice?
Answer
It decreases the melting point.
Question
How is the boiling point of a liquid affected by an increase in pressure?
Answer
The boiling point increases with an increase in pressure.
Question
Why does water boil at a higher temperature in a pressure cooker?
Answer
The steam is not allowed to escape, increasing the pressure and thus increasing the boiling point of the water.
Question
What is the effect of adding salt to water on its boiling point?
Answer
It increases the boiling point.
Question
On a heating curve graph for ice, what does a horizontal section represent?
Answer
A change of phase occurring at a constant temperature (e.g., melting or boiling).
Question
Why is cooking difficult at high altitudes?
Answer
Atmospheric pressure is low, so water boils at a temperature lower than $100^\circ\text{C}$, providing insufficient heat to the food.
Question
What happens to the volume of $1\text{ g}$ of ice at $0^\circ\text{C}$ when it melts into water?
Answer
Its volume decreases (from $1.091\text{ cm}^3$ to $1\text{ cm}^3$).
Question
Define 'sublimation'.
Answer
The direct change from the solid phase to the vapour phase.
Question
What is the specific heat capacity of ice compared to water?
Answer
Ice has a specific heat capacity of $2100\text{ J kg}^{-1}\text{ K}^{-1}$, which is half that of water.
Question
In the context of heat transfer, what is 'convection'?
Answer
A process of heat loss in liquids and gases where warmer parts rise and cooler parts sink (avoided in calorimeters by using a lid).
Question
How does polishing the outer surface of a calorimeter help in its function?
Answer
It reduces the loss of heat due to radiation.
Question
What happens to the internal energy of a hot body when it is placed in contact with a cold body?
Answer
It decreases as heat energy flows to the cold body.
Question
Does temperature alone tell us the quantity of thermal energy contained in a body?
Answer
No, thermal energy also depends on the mass and material of the body.
Question
Why is water at $0^\circ\text{C}$ used as a heat reservoir for wine bottles in cold countries?
Answer
Water can impart a large amount of heat before reaching its freezing point, preventing the bottles from freezing.