Question

when frozen carbon dioxide (co2) is heated, it changes directly into a gas. which statement best indicates that a physical change has taken place? heat caused a change in state. heat caused a decrease in energy. heat caused a new substance to form. heat caused an increase in gas production.

Explanation:

A physical change involves a change in the state of matter without altering the chemical composition of the substance. When frozen carbon - dioxide (dry ice) changes directly into a gas (sublimation), it is a change in state. Heat causing a change in state is characteristic of a physical change. A decrease in energy is not relevant here as heat is being added. The formation of a new substance indicates a chemical change, not a physical one. An increase in gas production could be due to a chemical reaction as well. But a change in state is a clear sign of a physical change.

Answer:

Heat caused a change in state