Chapter 11 - Thermal Properties of Matter Flashcards
Define Heat Capacity
The amount of thermal requires to raise the temperature of a substance by 1 kelvin/ 1 degree celsius
Heat capacity depends on Mass and ______ ?
Type of material
Formula for heat capacity
Heat energy = Heat Capacity x Temperature Change
S.I Unit for heat capacity
J/ Degree Celsius or Kelvin
S.I Unit for Heat ENERGY
Joules (J)
Why can changes in temperature can be given in either Kelvin or Degree Celsius?
When we talk about the change in temperature, the unit is not important, rather, the Value is the most important
Heat energy absorbed by a body
=
_____ in the ______ energy of the molecules
=
_____ _____ due to movement of the molecules
+
_____ _____ due to the intermolecular forces
Increase in the internal energy
Kinetic Energy
Potential Energy
A rise in temperature will take place if ?
ONLY the average kinetic energy of the molecule increase
A CHANGE of state will occur if ?
ONLY the potential energy of the molecules changes
Potential energy of the molecules is depend on which 2 condition?
Intermolecular forces
Space between intermolecular forces
Define SPECIFIC heat capacity
The amount of thermal energy requires to raise the temperature of a unit mass of a substance by 1 Kelvin / 1 Degree Celsius
S.I. Unit of Specific heat capacity
J/kg Kelvin or Degree Celsius
Formula for specific heat capacity
Heat capacity = MASS x Specific heat capacity
If Iron has a specific heat capacity of 460J/ kg Kelvin, what does it mean?
It means that 460 J of HEAT energy is required to raise the temperature of 1 kg of iron by 1 Kelvin
Formula linking Heat ENERGY and SPECIFIC heat capacity
Heat energy = Mass x Specific Heat Capacity x Temperature Change
What is the law of conservation of energy
Thermal energy lost = Thermal energy gained
Formula of ENERGY
Energy = Power x Time
Formula linking Power and Specific Heat capacity
Usually use in Qn that consist of a heater and a substance to find out the Specific Heat Capacity
Power x Time = Mass x Specific Heat Capacity x Temperature Change
Explain how a sea breeze occur?
Due the land have a much smaller heat capacity than the water in the sea, the land heat up faster, causing a difference in temperature between the land and the sea. Due to convection, which hot air will rise up and cold air will rush in to replace the hot air, the sea breeze then occur as the movement of cold air. (Wind = movement of air)
During the change of state, what happen to the temperature?
Remain constant
Melting and Freezing only occur at a DEFINITE temperature provided that ?
The substance is pure
Why during the change of state, the temperature of the substance is unchanged/
ALL thermal energy absorbed is used to BREAK the strong BONDS between particles.
The particles can MOVE OUT of their FIXED position
Hence they are further apart from one another
Thus the change of state occurs
Only the total INTERNAL POTENTIAL Energy is increased, not the kinetic energy
Define latent heat of fusion
The amount of thermal energy required to change a substance from solid state to liquid state, WITHOUT a change in temperature
S.I Unit for Latent heat of fusion/vaporisation
Joules (J)
Define specific latent heat of fusion
The amount of thermal energy required to change a unit mass of substance from solid state to liquid state, WITHOUT a change in temperature
S.I Unit for Specific Latent heat of fusion/vaporisation
J/Kg
Formula linking Latent heat of FUSION and Specific latent heat of FUSION
Lf = Mass x &f
Define latent heat of vaporisation
The amount of thermal energy required to change substance from LIQUID state to GASEOUS state, WITHOUT a change in temperature
Define SPECIFIC latent heat of vaporisation
The amount of thermal energy required to change a unit mass of a substance from LIQUID state to GASEOUS state, WITHOUT a change in temperature
Formula linking Latent heat of vaporisation and specific latent heat of vaporisation
Lv = Mass x &v
During boiling, why the temperature of water remains constant even when thermal energy is continuously absorbed by the water molecules?
ALL the LATENT HEAT absorbed is used to break the strong intermolecular bonds between the water molecules. Also to overcome the atmospheric pressure in order to escape into the air. The molecules are then able to move further apart from each other. During the process, latent heat is only used to increase the total internal potential energy. When these happens, a change of state takes place, water become steam.
How are pressure and impurities affects the boiling and melting points?
Impurities lowers the melting points
Impurities raise the boiling points
Pressure lowers the melting points
Pressure lowers the boiling points
For condensation and freezing, what is lost from the substance?
Latent heat is lost
What are the 6 differences between boiling and evaporation?
Boiling occurs at a fixed temperature
Evaporation occur at any temperature
Boiling take place throughout the liquid
Evaporation take place only on the surface of water
Boiling is a fast process
Evaporation is a slow process
Boiling requires an external thermal energy source
Evaporation does not require an external thermal energy source
Temperature remain constant during boiling
Temperature may change during evaporation
Bubbles are formed during boiling
No bubbles formed during evaporation
What are the 2 similarities of boiling and evaporation?
It involves a CHANGE OF STATES from liquid to gas
Both requires LATENT HEAT
4 factors affects rate of evaporation, Rate of evaporation increase if:
Temperature increases Surface area increases Humidity decreases Speed of the movement of surrounding air increases (wind)
How evaporation caused cooling in the ETHER Experiment? What are the observation and explanation for the experiment?
After the experiment conducted for some time, the break sticks to the wooden block.
The water between the wooden block and the breaker freeze and form a thin layer of ice
As the ether evaporates, cooling takes place and cause the temperature of the ether to decrease.
When the temperature of ether is decreased to a value that is lower than the water, the heat energy is then flow from the pool of water to the ether. Eventually, the temperature of the water will fall to 0 degree celsius and thus freezing occurs.
Using the kinetic theory, explain why evaporation cause cooling
According to the kinetic theory, the molecules in liquid moves in a continuous random motion. The molecules are moving at a DIFFERENT SPEED. The AVERAGE Kinetic energy of the molecule is proportional to the temperature of the liquid.
The fast moving molecules, especially the ones who are nearer to the surface of the liquid, will overcome the intermolecular force between itself and the neighboring molecule and escape into the air.
The liquid thus left with slower moving molecules and this causes the average kinetic energy of the molecule to decrease, results in a decrease in temperature of the liquid, and thus cooling takes place.
