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Difficulty: EasyChemical Reactions and Compounds

A student performs several classroom experiments to study how substances interact. Which of the following processes represents a chemical change?

  1. A
    Melting an ice cube into liquid water
  2. B
    Crushing a solid piece of chalk into fine powder
  3. Baking bread dough into a loaf of breadAnswer
  4. D
    Dissolving granulated sugar in warm water

Answer

Baking bread dough into a loaf of bread represents a chemical change.
Baking bread is a chemical change because thermal energy causes chemical reactions among ingredients (such as gas production and protein structural changes), resulting in new substances that cannot be converted back by simple physical means.

Step-by-Step Solution

1
Recall the distinction between chemical and physical changes.
A chemical change results in the formation of one or more new substances through the breaking and forming of chemical bonds, whereas a physical change alters only the form, state, or appearance of matter without changing its chemical identity.
This criterion allows accurate categorization of each observed process.
2
Evaluate each choice against the definition of a chemical change.
Melting ice, crushing chalk, and dissolving sugar all preserve the original chemical composition of the materials. In contrast, baking bread involves heat-driven chemical reactions that form completely new compounds.
Only baking creates new substances with distinct chemical properties.

Key Concept

Differentiating chemical changes (which form new chemical substances) from physical changes (which alter physical state or appearance without changing molecular composition).
Estimated Time:45s
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Topics

Chemical Reactions and Compounds

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