Question

Interpreting Concepts a. Is breaking an egg an example of a physical or chemical change? Explain your answer. b. Is cooking an egg an example of a physical or chemical change? Explain your answer.

Short answer

a. Physical change. b. Chemical change.

Step-by-step solution

- Identify the type of change for breaking an egg

Breaking an egg involves cracking and separating its contents but does not alter its chemical composition. Since the egg's internal proteins and nutrients remain the same, only their physical form changes. Hence, breaking an egg is an example of a physical change.

- Explanation for breaking an egg

A physical change affects the shape, size, or state of matter without changing its chemical nature. Since breaking an egg does not change its internal structure, it is deemed a physical change.

- Identify the type of change for cooking an egg

Cooking an egg involves applying heat, which causes the egg proteins to denature and coagulate, fundamentally altering its chemical structure. This transformation is irreversible and results in new chemical substances, classified as a chemical change.

- Explanation for cooking an egg

Chemical changes result in the formation of one or more new substances with different properties from the original. When an egg cooks, its proteins change composition, making it a chemical change.

Key concepts

Physical Change

A physical change occurs when the form of matter is altered but one substance is not transformed into another. Examples of physical changes include changes in size, shape, state (such as ice melting into water), and changes in texture.
A classic example is breaking an egg. When you break an egg, you are simply cracking its shell and separating the yolk and white. The chemical composition of the egg remains unchanged. It is still made up primarily of proteins, fats, water, and other compounds.

• The key aspect to remember: the internal substances of the egg are not altered.

So, breaking an egg is categorized as a physical change because its composition stays consistent. The structure may appear different, but at the molecular level, nothing new is created or destroyed.

Chemical Change

A chemical change involves a process where one or more substances are transformed into completely new substances with new chemical properties. Indicators of chemical changes can include color change, gas formation, temperature change, or the formation of a precipitate.
For instance, when cooking an egg, you apply heat that induces the proteins in the egg to denature and form new bonds, leading to coagulation. The clear egg white turns white and firm, and the yolk becomes solid. These are clear signs of a chemical change.

• New substances are formed with different properties.
• The process is usually irreversible under normal conditions.

In this process, the egg's chemical structure is fundamentally altered, making cooking an egg a chemical change.

Chemical Composition

Chemical composition refers to the identity and relative number of the elements that make up any given compound. In simpler terms, it is what things are made up of at a molecular level.
When we talk about breaking an egg, its chemical composition (main elements, proteins, fats, etc.) remains the same. Hence, it remains classified as a physical change. However, during cooking, the application of heat changes the chemical composition of the egg proteins, making it a chemical change.

• Physical changes do not affect the chemical composition of a substance.
• Chemical changes result in a new chemical composition.

Understanding chemical composition helps differentiate between physical and chemical changes, as it highlights whether the substance has remained the same or transformed into something new.