Question

Analyze Is gas escaping from an opened soft drink an example of a chemical or a physical change? Explain.

Short answer

Gas escaping from an opened soft drink is an example of a physical change. This is because the process involves carbon dioxide (CO2) transitioning from a dissolved state in the liquid to a gaseous state without any alteration in its chemical composition. No new substances are formed, and the change is only related to the appearance and physical state of the substances involved.

Step-by-step solution

Understand the difference between chemical and physical changes

A physical change is a change in the form or appearance of a substance without altering its chemical composition. Examples of physical changes include boiling water, melting ice, and breaking a glass. A chemical change, on the other hand, involves a change in the chemical composition of a substance, meaning new substances with different properties are formed. Examples of chemical changes include burning wood, rusting iron, and digesting food.

Analyze the process of gas escaping from an opened soft drink

When a soft drink is opened, carbon dioxide gas (CO2) escapes from the liquid. This occurs because the CO2 was previously dissolved in the liquid under pressure, but once the container is opened, the pressure is reduced, and the CO2 is released and becomes a gas. This process does not involve any alteration of the chemical composition of the liquid or the carbon dioxide. No new substances are formed, and the only change is related to the appearance and physical state of the substances involved.

Determine if the process is a chemical or physical change

As we have analyzed the process of gas escaping from an opened soft drink and observed that there is no change in the chemical composition of the substances involved, we can conclude that this process is a physical change, not a chemical change. The CO2 remains chemically unchanged and simply transitions from a dissolved state in the liquid to a gaseous state.

Key concepts

Physical Change

When considering physical changes in matter, the focus is on changes in the state or form that do not affect the substance's core identity. An excellent example is opening a fizzy drink, where the gas, once trapped under pressure, effervesces once the pressure is released after opening. This change is akin to the transition of water to steam or ice. These alterations are reversible; for example, releasing carbon dioxide (CO2) from a soda doesn't alter the gas's fundamental properties. It's simply CO2 shifting from one state of matter (dissolved in the liquid) to another (a gas in the air).

In daily life, physical changes are ubiquitous; for instance, cutting a sheet of paper, crushing a can, or dissolving sugar in water. It's crucial to recognize that the substances still retain their initial chemical composition despite these physical transformations. For more clarity, the gas escaping from an opened soft drink is indicative of a physical change, prominently visible and yet not altering the CO2 chemically.

Chemical Composition

Chemical composition refers to the identity and proportions of the atoms that constitute a particular chemical compound. Understanding this concept is essential as it distinguishes between physical and chemical changes in substances. A chemical change involves reconfiguration at the molecular level, producing entirely new substances with new properties. Combustion, rusting, or souring milk all exemplify chemical changes where original substances cease to retain their identity and new substances emerge with distinct chemical compositions.

For students to grasp the concept of chemical composition, remember that any change implying a difference in the arrangement, types, or quantities of atoms within a substance signals a chemical change. In contrast, if the atoms and their respective compositions remain intact during a change, such as with the CO2 escaping from that opened soft drink, we're looking at a physical change without any alteration to the chemical composition.

States of Matter

Understanding the states of matter is pivotal in identifying the nature of changes that occur in substances. There are traditionally three states of matter: solid, liquid, and gas. Each state is characterized by specific properties related to the arrangement and motion of molecules. Solids have a fixed shape and volume, liquids have a defined volume but adapt to the shape of their container, and gases occupy any volume available to them, spreading out to fill a container of any size.

Transitions between these states are typically physical changes. The carbon dioxide gas in a soft drink, for example, is forced into the liquid under pressure, becoming part of the liquid in a dissolved form—a liquid state. When the pressure is released, the CO2 exits the liquid and becomes a gas—a gaseous state. This is a simple demonstration of how matter transitions between different states due to physical changes, with practical applications even in how beverages are carbonated and served.