Question

These multiconcept problems (and additional ones) are found interactively online with the same type of assistance a student would get from an instructor. Which of the following describes a physical change? a. Paper is torn into several smaller pieces. b. Two clear solutions are mixed together to produce a yellow solid. c. A match burns in the air. d. Sugar is dissolved in water.

Short answer

Option A: Paper is torn into several smaller pieces represents a physical change, as the composition of the paper remains unchanged. Option D: Sugar is dissolved in water also represents a physical change, as it does not create a new substance, but its composition remains the same.

Step-by-step solution

Option A: Paper is torn into several smaller pieces.

In this option, we are simply changing the size and shape of the paper, but its composition remains unchanged (it's still made of paper). This represents a physical change.

Option B: Two clear solutions are mixed together to produce a yellow solid.

This option involves two substances reacting to form a new substance with different properties (a yellow solid). This indicates a change in chemical composition and is considered a chemical change.

Option C: A match burns in the air.

When a match burns, it undergoes a combustion reaction where the chemicals in the match head react with oxygen in the air and produce new substances like gases, ash, and heat. This is also a chemical change.

Option D: Sugar is dissolved in water.

When sugar dissolves in water, it simply changes from a solid to a dispersed state in a liquid medium, but its composition remains the same. It does not create a new substance. Therefore, this is a physical change. So, based on the analysis of each option,

Answer:

Option (a) and (d) describe physical changes.

Key concepts

Chemistry Education

Chemistry education is a field centered on disseminating knowledge about the study of matter, its properties, and the changes it undergoes. In chemistry education, students learn to differentiate between physical and chemical changes—a fundamental concept for understanding how matter interacts.

Effective chemistry education aims to provide clear explanations and appropriate examples to illustrate these changes. For example, when a student encounters a multistep problem about identifying physical and chemical changes, they would benefit from a step-by-step analysis of each answer option, linking back to the core definitions and characteristics of physical and chemical changes. This approach encourages critical thinking and a deeper comprehension of why certain changes in matter are classified differently.

Physical Change

A physical change refers to a process where the form of matter is altered, but its identity remains unchanged. These changes are generally reversible and do not involve a new substance being formed. Common examples include the changes in the state of matter, such as melting, freezing, or evaporation.

In the textbook exercise, tearing a piece of paper and dissolving sugar in water are considered physical changes because they do not result in the production of new substances. Tearing changes only the shape and size, while dissolving modifies the distribution of sugar molecules in water. Understanding these nuances helps students to classify and predict the outcomes of various processes in the physical world.

Chemical Change

A chemical change occurs when a substance transforms into one or more new substances with different properties. These changes are generally irreversible and involve a rearrangement of atoms. Indicators of chemical changes include color changes, temperature changes, gas production, and the formation of a precipitate.

In our exercise, mixing two solutions to form a yellow solid and the burning of a match both represent chemical changes. They produce new substances altogether, indicated by the visible color change and the formation of ash and gases, respectively. Clarifying this distinction is crucial for students who need to recognize how chemical reactions underpin practically every process in nature and technology.

Matter and Its Properties

Matter is anything that has mass and occupies space. It is composed of atoms and molecules, which determine its physical and chemical properties. Physical properties are observable and measurable without changing the substance’s composition—such as density, melting point, and solubility. Chemical properties describe a substance's ability to undergo specific chemical changes, like flammability and acidity.

The properties of matter are intrinsically linked to physical and chemical changes, as understanding them allows prediction of how substances will react under different conditions. This foundational knowledge supports all other studies within chemistry and is applied when solving problems related to the behavior of matter, much like the textbook exercise in question.