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Questions and Answers
What marks the melting point of pure ice on the Celsius scale?
What marks the melting point of pure ice on the Celsius scale?
- 0°C (correct)
- 100°C
- 273.16°C
- 32°C
What is the relationship between a temperature increase of 1 kelvin and Celsius?
What is the relationship between a temperature increase of 1 kelvin and Celsius?
- They are unrelated.
- 1 kelvin equals a temperature decrease of 1°C.
- 1 kelvin equals 1°C plus 100.
- 1 kelvin is equal to an increase of 1°C. (correct)
When do two objects reach thermal equilibrium?
When do two objects reach thermal equilibrium?
- When there is no net transfer of thermal energy between them. (correct)
- When one object is hotter than the other.
- When both objects are at different temperatures.
- When thermal energy flows from the cooler object to the hotter object.
In which phase do molecules have the least kinetic energy?
In which phase do molecules have the least kinetic energy?
What allows gas molecules to travel freely and collide elastically?
What allows gas molecules to travel freely and collide elastically?
What happens to the electrostatic potential energy in the gaseous phase?
What happens to the electrostatic potential energy in the gaseous phase?
What characterizes the movement of gas molecules in Brownian motion?
What characterizes the movement of gas molecules in Brownian motion?
Which statement about molecules in solids is true?
Which statement about molecules in solids is true?
What happens to the kinetic energy of molecules when a substance is heated without changing its state?
What happens to the kinetic energy of molecules when a substance is heated without changing its state?
What occurs to the potential energy of a substance during a phase change from solid to gas?
What occurs to the potential energy of a substance during a phase change from solid to gas?
What is the definition of specific heat capacity?
What is the definition of specific heat capacity?
At what temperature does absolute zero occur?
At what temperature does absolute zero occur?
What is the primary energy form contributing to internal energy at absolute zero?
What is the primary energy form contributing to internal energy at absolute zero?
How can specific heat capacity be determined using the method of mixtures?
How can specific heat capacity be determined using the method of mixtures?
Which of the following equations represents the relationship involving specific heat capacity?
Which of the following equations represents the relationship involving specific heat capacity?
What occurs as a substance changes phase regarding temperature?
What occurs as a substance changes phase regarding temperature?
What is the relationship between the pressure and the volume of a gas at constant temperature according to Boyle's law?
What is the relationship between the pressure and the volume of a gas at constant temperature according to Boyle's law?
During an elastic collision of gas atoms with the walls of a container, what is the change in momentum represented by?
During an elastic collision of gas atoms with the walls of a container, what is the change in momentum represented by?
Which ideal gas law states that volume is directly proportional to temperature at constant pressure?
Which ideal gas law states that volume is directly proportional to temperature at constant pressure?
In the kinetic theory of gases, which force is considered negligible except during collisions?
In the kinetic theory of gases, which force is considered negligible except during collisions?
What happens to the average force exerted by a gas atom on the walls of a container during a collision?
What happens to the average force exerted by a gas atom on the walls of a container during a collision?
Which equation reflects the relationship derived from combining Boyle's and Charles' laws?
Which equation reflects the relationship derived from combining Boyle's and Charles' laws?
How can Boyle's law be experimentally investigated?
How can Boyle's law be experimentally investigated?
What does the sum of the forces from all atom collisions against the container's wall represent?
What does the sum of the forces from all atom collisions against the container's wall represent?
What is the primary purpose of using an insulator during the measurement of energy transfer?
What is the primary purpose of using an insulator during the measurement of energy transfer?
What does the specific latent heat of fusion refer to?
What does the specific latent heat of fusion refer to?
How is the specific latent heat, L, calculated in the formula E = mL?
How is the specific latent heat, L, calculated in the formula E = mL?
What is Avogadro's constant and its significance in chemistry?
What is Avogadro's constant and its significance in chemistry?
Which formula is used to determine the number of moles, n, in a substance?
Which formula is used to determine the number of moles, n, in a substance?
In kinetic theory, which assumption is NOT true for an ideal gas?
In kinetic theory, which assumption is NOT true for an ideal gas?
What occurs to the temperature of a substance during a phase change?
What occurs to the temperature of a substance during a phase change?
What is the unit for specific latent heat, L?
What is the unit for specific latent heat, L?
What is the value of the Boltzmann constant?
What is the value of the Boltzmann constant?
How can the equation of state for an ideal gas be rewritten using the Boltzmann constant?
How can the equation of state for an ideal gas be rewritten using the Boltzmann constant?
What happens to the mean kinetic energy of gas molecules when the temperature increases?
What happens to the mean kinetic energy of gas molecules when the temperature increases?
Which equation represents the relationship between pressure, number of molecules, and their velocity squared?
Which equation represents the relationship between pressure, number of molecules, and their velocity squared?
What is the significance of the internal energy of an ideal gas?
What is the significance of the internal energy of an ideal gas?
In the context of ideal gases, what does the term 'mean kinetic energy' denote?
In the context of ideal gases, what does the term 'mean kinetic energy' denote?
What assumption is made about the potential energy in an ideal gas model?
What assumption is made about the potential energy in an ideal gas model?
How is the relationship between the kinetic energy and the Boltzmann constant expressed?
How is the relationship between the kinetic energy and the Boltzmann constant expressed?
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Study Notes
Temperature Scales
- Celsius (°C) : Sets the melting point of pure ice at 0°C and the boiling point of water at 100°C at atmospheric pressure.
- Thermodynamic Scale (Kelvin): Uses the triple point of pure water (273.16 K) and absolute zero as fixed points. A change in temperature of 1 Kelvin matches a 1°C change.
- T(K) = T(°C) + 273.16
Thermal Equilibrium
- Thermal energy flows from hotter to cooler objects until they reach the same temperature and there's no net energy transfer.
- Two objects are in thermal equilibrium when there is no net transfer of thermal energy between them.
Solids, Liquids, and Gases
- Solids are tightly packed, strong electrostatic forces, and molecules vibrate around fixed positions.
- Liquids have greater intermolecular spacing, weaker electrostatic forces, and molecules can move around.
- Gases have the most kinetic energy, molecules move rapidly and freely, negligible electrostatic forces.
Brownian Motion
- Random motion of particles (like smoke in air) caused by collisions with gas molecules.
- Demonstrates the kinetic nature of molecules.
Internal Energy
- The sum of kinetic and potential energies within a substance.
- Heating a substance increases kinetic energy while changing state increases potential energy.
Absolute Zero
- 0K: All molecular movement stops, minimal internal energy.
- Internal energy is solely from electrostatic potential energy at this point.
Specific Heat Capacity
- Energy needed per unit mass to raise the temperature by 1 Kelvin.
- Formula: E = mc∆θ (E = energy, m = mass, c = specific heat capacity, ∆θ = temperature change).
- Units: Jkg-1K-1.
Specific Latent Heat
- Energy required per unit mass to change the state of a substance.
- Latent heat of fusion (Lf): Solid to liquid.
- Latent heat of vaporization (Lv): Liquid to gas.
- Formula: E = mL (E = energy, m = mass, L = specific latent heat).
- Units: Jkg-1.
Amount of Substance
- Measured in moles: 1 mole contains 6.02 x 10^23 particles (Avogadro's constant).
- Number of moles (n) = mass (m) / molar mass (M).
Kinetic Theory of Gases Assumptions
- Large number of molecules moving randomly and rapidly.
- Gas molecule volume is negligible compared to container volume.
- All collisions are perfectly elastic.
- Collision time is negligible compared to time between collisions.
- Electrostatic forces are negligible except during collisions.
Pressure
- Gas molecules collide elastically with the container walls.
- These collisions create an average force, leading to pressure.
- Total pressure: Sum of forces from all collisions divided by container wall area.
Ideal Gas Laws
- Boyle's Law: For a fixed mass of gas at constant temperature, pressure is inversely proportional to volume.
- Charles' Law: For a fixed mass of gas at constant pressure, volume is directly proportional to temperature.
- These laws combined: pV/T = k (k = constant).
- Equation of state for ideal gases: pV = nRT (p = pressure, V = volume, n = moles, R = molar gas constant, T = temperature).
Boltzmann Constant
- k = R/N A (R = molar gas constant, NA = Avogadro's constant).
- Value: 1.38 x 10^-23 JK-1.
- Alternate equation for ideal gas state: pV = NkT (N = number of molecules).
Mean Kinetic Energy and Temperature
- Kinetic energy of gas molecules is proportional to temperature (Kelvin).
- At a given temperature, all gas molecules have the same mean kinetic energy.
- Heavier molecules have lower root-mean-square (rms) speed.
- Relationship between kinetic energy and temperature: 𝐸𝑘 = 3/2 kT (𝐸𝑘 = mean kinetic energy).
Internal Energy of an Ideal Gas
- Internal energy = sum of kinetic and potential energies.
- In an ideal gas, there is no potential energy due to negligible electrostatic forces.
- Internal energy is entirely kinetic energy, therefore proportional to temperature.
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