Problem 82 - Chemistry: Principles and Reactions

Question

Determine whether the statements given below are true or false. Consider specific heat. (a) Specific heat represents the amount of heat required to raise the temperature of one gram of a substance by \(1^{\circ} \mathrm{C}\). (b) Specific heat is the amount of heat flowing into the system. (c) When 20 J of heat is added to equal masses of different materials at \(25^{\circ} \mathrm{C}\), the final temperature for all these materials will be the same. (d) Heat is measured in \({ }^{\circ} \mathrm{C}\).

Step-by-Step Solution

Answer

Question: Determine whether the following statements about specific heat are true or false. a) Specific heat represents the amount of heat required to raise the temperature of one gram of a substance by \(1^{\circ} \mathrm{C}\). b) Specific heat is the amount of heat flowing into a system. c) When 20 J of heat is added to equal masses of different materials at \(25^{\circ} \mathrm{C}\), the final temperature for all these materials will be the same. d) Heat is measured in \({ }^{\circ} \mathrm{C}\). Answer: a) True b) False c) False d) False

Step 1: (Statement a - Evaluation)

Specific heat does indeed represent the amount of heat required to raise the temperature of one gram of a substance by \(1^{\circ} \mathrm{C}\). Therefore, statement (a) is True.

Step 2: (Statement b - Evaluation)

Specific heat is not the amount of heat flowing into the system. Specific heat is a property of a substance that describes its ability to absorb heat relative to its mass and change in temperature. The amount of heat flowing into a system depends on the specific heat, mass, and change in temperature of the substance. Therefore, statement (b) is False.

Step 3: (Statement c - Evaluation)

When 20 J of heat is added to equal masses of different materials at \(25^{\circ} \mathrm{C}\), the final temperature for all these materials will not necessarily be the same. Different materials have different specific heat capacities, meaning that every substance will heat up differently as it absorbs heat. So, statement (c) is False.

Step 4: (Statement d - Evaluation)

Heat is not measured in \({ }^{\circ} \mathrm{C}\). Instead, heat is measured in units of energy, such as Joules (J) or calories (cal). The \({ }^{\circ} \mathrm{C}\) unit is used to measure temperature, not heat. Therefore, statement (d) is False.

Key Concepts

Thermodynamics

Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, radiation, and physical properties of matter. The behavior of these quantities is governed by the four laws of thermodynamics, which can be precisely defined using specific heat concepts.

Specific heat, as correctly outlined in the exercise, is a fundamental concept within thermodynamics that relates to the amount of heat required to change a substance's temperature. This thermodynamic property is critical for understanding how energy is transferred as heat and how it affects different substances. It plays a significant role in various applications, such as designing heating and cooling systems, studying climate change, and even in culinary endeavors where the cooking temperature must be carefully managed.

Heat Capacity

Understanding heat capacity is essential for grasping thermodynamic processes. Heat capacity is an extensive property of matter, representing the amount of heat required to change the temperature of an object by a given amount. While the specific heat is a particular value per unit mass, heat capacity takes into account the entire mass of the object.

For instance, when two different substances have the same mass, it may take different amounts of energy to change their temperatures. This is because of the different specific heat values. An object with high heat capacity can absorb a lot of heat without significantly changing its temperature, making materials like water especially good for thermal storage.

Energy Units

In the context of thermodynamics and specific heat, Energy units are essential for quantifying heat and work. The most common energy unit in the International System of Units (SI) is the joule (J), named after James Prescott Joule. Other units such as the calorie (cal), British thermal unit (BTU), and kilowatt-hour (kWh) are also used in various contexts.

One calorie is defined as the amount of heat required to raise the temperature of one gram of water by one degree Celsius. In the exercise, the use of joules illustrates an example of measuring the transfer of heat energy. Misunderstanding temperature as a measure of heat, such as in degrees Celsius, can lead to incorrect assumptions, as temperature is merely a measure of thermal energy's intensity, not its total quantity within a substance.