Thermodynamics Chapter 18: Temperature and Heat

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Questions and Answers

What formula represents the relationship between heat capacity and temperature change?

Q = C ΔT (correct)

Q = ncm ΔT

Q = mc ΔT

Q = C/m

How is specific heat capacity defined?

As heat capacity per mole of substance

As heat capacity per unit mass (correct)

As heat capacity divided by volume

As the total heat exchanged divided by temperature change

In the specific heat formula c = Q/mΔT, what does 'm' represent?

The initial temperature

The number of moles

The heat capacity

The mass of the substance (correct)

What is the unit for molar specific heat?

cal/mol-C° Signup and view all the answers

When calculating heat transfer for a substance with a known specific heat, what factors must be considered?

Temperature change and mass Signup and view all the answers

If an object with a heat capacity of 5 cal/°C changes its temperature by 10°C, how much heat is absorbed?

50 cal Signup and view all the answers

For a given substance, which equation best describes molar heat capacity?

Q = ncm ΔT Signup and view all the answers

Which statement accurately describes heat as it relates to temperature difference?

Heat is energy transferred due to a temperature difference. Signup and view all the answers

What is the heat of fusion for water in joules per kilogram?

333,000 J/kg Signup and view all the answers

How much energy is required to vaporize one kilogram of water at its boiling point?

2256 kJ Signup and view all the answers

What is the formula used to calculate the energy transferred for a phase change?

Q = mL Signup and view all the answers

If 260 g of liquid water at its freezing point loses 50.2 kJ of heat, which equation could be used to find the mass of ice formed?

m = Q/Lf Signup and view all the answers

What is the specific heat capacity of silver given in the content?

236 J/kg-K Signup and view all the answers

What is the total energy required to completely melt 130 g of silver from 15.0° C at its melting point?

4.27 x 10^4 J Signup and view all the answers

When liquid water is freezing, which process is being described?

Heat is released. Signup and view all the answers

Which of the following statements regarding latent heat of vaporization is true?

It is the energy needed to vaporize a liquid. Signup and view all the answers

What is the specific heat of the substance when 314 J is added as heat to a 30.0 g sample resulting in a temperature rise from 25.0°C to 45.0°C?

523 J/kg-K Signup and view all the answers

What is the molar specific heat of the substance calculated from the given data?

26.2 J/mol-K Signup and view all the answers

How many moles are present in a 30 g sample of a substance with a molar mass of 50.0 g/mol?

0.600 mol Signup and view all the answers

Which of the following correctly defines the latent heat of a substance?

Heat required to change the state of a material. Signup and view all the answers

When a solid absorbs heat and changes to a liquid, this process is called:

Latent Heat of Fusion Signup and view all the answers

In the context of heat transfer, which equation represents the relationship between power, heat, and time?

P = Q/t Signup and view all the answers

What happens to the temperature of a substance during a phase change, despite energy being added?

The temperature remains constant. Signup and view all the answers

If a sample requires 200 J to increase its temperature by 77 K, what is its specific heat capacity if the mass is 0.100 kg?

26.0 J/kg-K Signup and view all the answers

Study Notes

Chapter 18: Temperature, Heat, and the First Law of Thermodynamics

This chapter covers 2 lectures, spanning one week and 4 hours.
Lecture 1: Focuses on heat, temperature, the zeroth law of thermodynamics, heat absorption, heat capacity, specific heat capacity, molar specific heat, latent heat associated with fusion and vaporization, and related problems.
Lecture 2: Covers work done in thermodynamics, the first law of thermodynamics, and relevant applications along with related problems.

Thermodynamics

Thermodynamics is a branch of physics and engineering concerned with thermal energy (internal energy) in systems.
A central concept is temperature.

Temperature

Temperature is an SI base unit related to the sensation of hot and cold.
Measured using a thermometer containing a working substance whose measurable property (like length or pressure) changes according to temperature increase or decrease.

Temperature Scales

Kelvin (T): Temperature scale with absolute zero as its zero point
Celsius (T_c): Temperature scale using "°C" and relative to the freezing point of water
Fahrenheit (T_F): Another temperature scale using "°F"
Conversions: Tc = T-273.15; T_F = T_c +32

Zeroth Law of Thermodynamics

If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.
Implication: Two systems in thermal equilibrium have the same temperature.

Absorption of Heat

A change in temperature is due to a change in the system's thermal energy resulting from energy transfer between the system and its environment. This transferred energy is heat (Q)
Heat (Q): Positive when energy flows into the system (absorbed), negative when energy flows out of the system (released).
1 cal = 3.968 x 10^-3 Btu = 4.1868 J

Heat Capacity

The heat capacity (C) of an object is the proportionality constant between the heat absorbed (Q) and the resulting temperature change (ΔT).
Q = C ΔT or C = Q/ΔT
Unit: cal/°C or J/K

Specific Heat Capacity

Specific heat (c) is the heat capacity per unit mass.
c = C/m or C = mc
Unit: cal/g°C or J/kgK

Molar Specific Heat

Molar specific heat (c_m) is the heat capacity per mole of the substance.
Q = n c_m ΔT or c_m = Q /n ΔT
Unit: cal/mol°C or J/molK

Heats of Transformation

Specific Heat: Heat needed to change the temperature of the substance without changing state. Q = mc∆T
Latent Heat: Heat required to change the state of a substance (e.g. solid to liquid) without changing temperature. Q = mL
Latent Heat of Fusion: Heat needed to change a substance from a solid to a liquid.
Latent Heat of Vaporization: Heat needed to change a substance from a liquid to a gas.

Phase Changes

Temperature remains constant during phase changes.
The amount of heat added (Q) during a phase change is Q = mΔT
Heat absorption during phase changes is Q = mL

Additional Problems and Practice

The text provides additional problems for practice on specific topics in Chapter 18.

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Description

This quiz explores Chapter 18 of Thermodynamics, focusing on key concepts such as temperature, heat, and the first law of thermodynamics. It covers important topics like heat capacity, specific heat, and work done in thermodynamic systems. Test your understanding of these critical principles and their applications.