Question

Heat required to raise the temperature of \(1 \mathrm{~mol}\) of a substance by \(1^{\circ}\) is called: (a) Specific heat (b) Molar heat capacity (c) Water equivalent (d) Specific gravity

Short answer

The correct answer is (b) Molar heat capacity.

Step-by-step solution

Understand the Definition

The question asks for the term that describes the amount of heat needed to raise the temperature of 1 mole of a substance by 1 degree Celsius. This is a key definition-based question in thermodynamics.

Option Analysis

Examine the given options: (a) Specific heat: Related to the amount of heat per unit mass to raise the temperature by 1 degree Celsius. (b) Molar heat capacity: Refers to the heat needed to raise 1 mole of a substance by 1 degree Celsius. (c) Water equivalent: Is not related to heat capacity directly. (d) Specific gravity: Relates to density comparison, not heat-related properties.

Select the Correct Option

Based on the definitions, the heat needed to raise the temperature of 1 mole of a substance by 1 degree Celsius is called "Molar heat capacity". Therefore, option (b) is the correct answer.

Key concepts

Thermodynamics

Thermodynamics is the branch of physics that deals with the relationship between heat, work, and energy in a system. It studies how energy is transferred from one place to another and how it affects matter. The fundamental principle of thermodynamics that ties into our discussion is the conservation of energy, or the first law of thermodynamics. This law states that energy cannot be created or destroyed, only transferred or converted from one form to another.
In the context of molar heat capacity, thermodynamics explains how heat energy is absorbed or released by a substance when its temperature changes. This includes exploring how molecules inside a substance store this heat energy and translate it to motion or internal energy. Understanding the thermodynamic principles is crucial for predicting how different substances react under changes in temperature.

Heat capacity

Heat capacity is an important concept in thermodynamics, as it describes how much heat a substance can absorb. It's a measure of the thermal energy required to change the temperature of an object by a certain amount. Molar heat capacity specifically refers to one mole of a substance.
This concept is crucial when considering how different materials respond to heat. Some key points related to heat capacity include:

• It depends on the material or substance—metals, for example, often have lower heat capacities than water.
• It is measured in joules per Kelvin (J/K) or joules per degree Celsius (J/°C).
• Molar heat capacity offers a standardized way to discuss thermal changes across different substances by focusing on moles, which helps remove variables like mass from the conversation.

Understanding heat capacity allows us to predict how a substance will behave when heated or cooled and is fundamental in designing systems that involve heating or cooling.

Mole concept

The mole concept is a basic idea in chemistry that allows chemists to count particles like atoms and molecules by weighing them. A mole is a unit that represents a very large number of atoms or molecules, specifically Avogadro's number, which is approximately \(6.022 \times 10^{23}\) entities.
When applied to topics like molar heat capacity, the mole concept becomes particularly useful. Molar heat capacity is measured per mole, meaning the amount of heat needed to raise one mole of a substance by one degree Celsius. This is valuable because:

• It provides a consistent way to compare how different substances handle heat on a per-molecule basis.
• It simplifies calculations in chemical reactions involving heat exchange.
• It connects the macroscopic properties that we measure in labs (like temperature and heat) with the microscopic world of molecules.

Overall, the mole concept bridges the gap between the atomic scale and the laboratory scale, making complex topics like molar heat capacity easier to understand and apply.