Question

What are the names of the thermal properties whose values can have the following units? (a) \(J \mathrm{~g}^{-1}{ }^{\circ} \mathrm{C}^{-1}\) (b) \(J \mathrm{~mol}^{-1}{ }^{\circ} \mathrm{C}^{-1}\) (c) \(J^{\circ} \mathrm{C}^{-1}\) (d) J

Short answer

(a) Specific heat capacity, (b) Molar heat capacity, (c) Heat capacity, (d) Heat energy or work related to heat transfer.

Step-by-step solution

Identify the Thermal Property for (a)

The units given in part (a) are a measure of thermal energy per gram per degree Celsius (\(J \text{ g}^{-1} \text{ }^\text{o}C^{-1}\)). This is the definition of specific heat capacity, which is the amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius.

Identify the Thermal Property for (b)

The units given in part (b) are a measure of thermal energy per mole per degree Celsius (\(J \text{ mol}^{-1} \text{ }^\text{o}C^{-1}\)). This refers to the molar heat capacity, which is the amount of heat required to raise the temperature of 1 mole of a substance by 1 degree Celsius.

Identify the Thermal Property for (c)

The units given in part (c) are a measure of thermal energy per degree Celsius (\(J^\text{o}C^{-1}\)). This unit is associated with the heat capacity of an object, which is the total amount of heat energy required to raise the temperature of the entire object by 1 degree Celsius.

Identify the Thermal Property for (d)

The unit given in part (d) is the joule (J), which is a measure of energy. In thermal context, it could refer to the quantity of heat energy transferred or the amount of work done related to heat transfer.

Key concepts

Specific Heat Capacity

Understanding the concept of specific heat capacity is fundamental in the study of thermal properties. It defines how much heat energy is needed to raise the temperature of a particular mass of a substance by a certain amount, typically one degree Celsius. For example, water has a high specific heat capacity (\(4.18 J \text{g}^{-1} \text{ }^\text{o}C^{-1}\)), which means it requires a lot of energy to change its temperature.

When working on problems involving specific heat capacity, the formula used is: \[ q = m \times c \times \triangle T \] where \(q\) is the heat energy in joules (J), \(m\) is the mass of the substance in grams (g), \(c\) is the specific heat capacity, and \(\triangle T\) is the change in temperature in degrees Celsius (°C). This property is intrinsic to the substance; for example, metals typically have a lower specific heat capacity compared to water, reflecting their tendency to heat up and cool down more quickly.

Molar Heat Capacity

The molar heat capacity is closely related to the specific heat capacity but is concerned with the amount of heat required to raise the temperature of one mole of a substance by one degree Celsius. It helps to compare the thermal properties of substances on a per-mole basis, which is particularly useful in chemistry when dealing with substances in moles.

The molar heat capacity (\(J \text{mol}^{-1} \text{ }^\text{o}C^{-1}\)) can be thought of as the collective specific heat of the atoms or molecules that constitute one mole of the substance. This is an important consideration when understanding energy changes in chemical reactions or physical processes. Different substances have different molar heat capacities, reflecting how they absorb and hold heat energy on a molecular level.

Heat Capacity

Heat capacity is a broader term that defines the amount of heat required to raise the temperature of an entire object or sample by one degree Celsius. It can be seen as an extensive property of matter, meaning it depends on the amount of the substance in question. Unlike specific or molar heat capacities, it doesn't refer to a per-unit mass or mole, but the whole sample.

The heat capacity (\(J^\text{o}C^{-1}\)) is vital when considering heating or cooling systems, where the total amount of heat energy involved in temperature changes of objects or environments needs to be calculated. Factors like the mass and specific heat capacity of the material will determine its heat capacity.

Heat Energy

Heat energy, measured in joules (J), is the form of energy transferred from one body to another as a result of a temperature difference. It is a key concept in thermodynamics and plays an essential role in everyday phenomena, from cooking food to powering engines.

When substances absorb or lose heat energy, their temperature changes, and this energy can be quantified using specific heat or heat capacity calculations. Understanding how different materials transfer heat energy is crucial for a wide range of applications, from designing thermal insulation to developing efficient cooling systems. It's the driving force behind the temperature changes and phase transitions that matter undergoes.