Problem 45 - Introductory Chemistry Atoms First

Question

What is the name of the process by which matter changes directly from the solid state to the gas state?

Step-by-Step Solution

Answer

The process by which matter changes directly from the solid state to the gas state is called sublimation. Examples of substances that undergo sublimation include dry ice (solid carbon dioxide) and solid iodine that turns into purple iodine vapor when heated.

Step 1: Define the Process

The process we are looking for is called sublimation. Sublimation is the transition of a substance directly from the solid phase to the gas phase, without passing through the intermediate liquid phase.

Step 2: Examples of Sublimation

Some common examples of substances that experience sublimation include dry ice (solid carbon dioxide) and solid iodine that turns into purple iodine vapor when heated.

Key Concepts

Phase Transition

Phase transition, an essential concept in physical science, refers to the transformation of matter from one state to another. Matter typically exists in three fundamental states: solid, liquid, and gas. The transitions between these states, such as melting (solid to liquid), freezing (liquid to solid), vaporization (liquid to gas), condensation (gas to liquid), and sublimation (solid to gas), involve energy changes.

Sublimation is a unique phase transition where a substance moves directly from a solid to a gaseous state, skipping the liquid phase entirely. This occurs under specific temperature and pressure conditions which are generally lower than those required for the substance to melt. For students learning about phase transitions, visualizing or experimenting with substances like dry ice can make the seemingly abstract concept feel more tangible.

Solid to Gas

Understanding the 'solid to gas' transition, it's crucial to know that not all substances pass through the liquid phase when they are heated. Sublimation is an excellent example of this direct transition and it is a fascinating phenomenon to observe. Each substance has a specific temperature, known as the sublimation point, at which it can undergo this process.

Factors affecting this transition include atmospheric pressure and the chemical properties of the substance. For instance, under normal atmospheric pressure, dry ice, which is solid carbon dioxide, sublimates at -78.5 degrees Celsius. This insightful observation can serve as a real-world application to help students grasp the phenomenon and its conditions.

Chemical Properties

Chemical properties are characteristics of a substance that become evident during a chemical reaction or, as in the case of sublimation, a phase transition. These properties are intrinsic to the substance and determine the behavior of the substance during these processes.

For example, the propensity of a substance to undergo sublimation is a unique chemical property. It depends on the strength of the intermolecular forces holding the substance in the solid state. Weak intermolecular forces may lead to easier sublimation under certain conditions. The understanding of the chemical properties and how they influence phase transitions is vital in chemistry and can predict the behavior of substances under various conditions. This contributes to the development of innovative materials and processes in science and industry.