Which statement best describes what happens during a chemical change

General
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which statement best describes what happens during a chemical change

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Which statement best describes what happens during a chemical change?

Answer:
During a chemical change, the original substances undergo a transformation to form new substances with different properties. This process involves the breaking and forming of chemical bonds, leading to a rearrangement of atoms.

Detailed Explanation:

  1. New Substances Formed: In a chemical change, the reactants (starting substances) react to create one or more new products. These products have different chemical properties and compositions compared to the reactants.

  2. Bond Formation and Breaking: Chemical changes involve making and breaking chemical bonds. For instance, in the combustion of wood, the cellulose in wood reacts with oxygen to produce carbon dioxide, water, and ash.

  3. Energy Changes: Chemical changes often involve energy changes. This can be in the form of heat, light, or sound. For example, exothermic reactions release energy (like burning wood), while endothermic reactions absorb energy (like photosynthesis).

  4. Irreversibility: Many chemical changes are irreversible under normal conditions. For example, once you bake a cake, you cannot easily revert it to its original ingredients (like flour, eggs, and sugar).

  5. Observable Indicators: Some common indicators of a chemical change include a change in color, the production of gas (bubbles), the formation of a precipitate (solid), and a change in temperature.

Example:

Consider the reaction between vinegar (acetic acid) and baking soda (sodium bicarbonate). When these substances mix, they undergo a chemical reaction to form carbon dioxide gas, water, and sodium acetate:

\text{CH}_3\text{COOH} + \text{NaHCO}_3 \rightarrow \text{CO}_2 \uparrow + \text{H}_2\text{O} + \text{NaCH}_3\text{COO}

In this reaction:

  • New substances (carbon dioxide, water, and sodium acetate) are produced.
  • Bonds are broken (in the acetic acid and sodium bicarbonate) and new bonds are formed (in water, carbon dioxide, and sodium acetate).

Conclusion:

To best describe what happens during a chemical change, you can say: “During a chemical change, the substances involved react to form new substances with different properties.” This encapsulates the essence of chemical changes, emphasizing the formation of new products with distinct characteristics from the reactants.