Which of the following is an example of a chemical change?
A.
Releasing compressed gas to make a bottle-rocket launch
B.
Adding water to clay to make slip
C.
Crystalizing honey to make candy
D.
Including baking soda in a recipe to make it less sour
The Correct answer and Explanation is:
The correct answer is D. Including baking soda in a recipe to make it less sour.
Explanation:
A chemical change occurs when a substance undergoes a transformation that results in the formation of one or more new substances with different chemical properties. This process involves breaking and forming chemical bonds, often accompanied by energy changes such as heat, light, or gas production.
Option D: Including baking soda in a recipe to make it less sour is a classic example of a chemical change. Baking soda (sodium bicarbonate, NaHCO₃) is a base that reacts with acidic components in the recipe (like vinegar, lemon juice, or yogurt). The reaction between the base (baking soda) and the acid produces carbon dioxide gas (CO₂), water (H₂O), and a salt (sodium acetate, in the case of vinegar). This reaction neutralizes the acid, reducing the sour taste and causing the batter or dough to rise. The formation of carbon dioxide gas, which creates bubbles, is a clear indicator that a chemical change has occurred, as new substances (CO₂, water, and a salt) are formed.
Option A: Releasing compressed gas to make a bottle-rocket launch is a physical change. The gas was under pressure, and when it is released, it expands and propels the rocket. However, the gas does not undergo a chemical transformation; it remains the same substance, only changing in state (from compressed to expanded).
Option B: Adding water to clay to make slip is also a physical change. The water simply disperses the clay particles, turning the solid into a liquid suspension, but no new substances are formed. The clay and water can be separated, and both would retain their original properties.
Option C: Crystallizing honey to make candy is another physical change. Honey is a supersaturated solution, and crystallization is the process of solidifying the sugar within the honey. The chemical composition of honey remains unchanged, as the crystallization involves only a change in the physical state.
In summary, a chemical change involves the creation of new substances, while physical changes do not. The inclusion of baking soda in a recipe, as described in option D, leads to a chemical reaction that produces new compounds, making it the correct example of a chemical change.