Tijuan mixed a solid and a liquid together in a beaker. He determined that a chemical change occurred.

Question

If his conclusion is correct, which substances could he have been observing and why?

ice mixed into warm oil, because the change of state that occurred when the ice melted cannot be reversed
baking soda mixed into vinegar, because the production of bubbles indicates that a new substance formed
sugar mixed into hot water, because the disappearance of solid indicates that the chemical identity of the sugar changed
sand mixed into water, because when sand was added the mass of the beaker increased

Answer 1

Tijuan's conclusion that a chemical change occurred can be best supported by the second option: baking soda mixed into vinegar, because the production of bubbles indicates that a new substance formed.

Here's the reasoning for each option:

1. Ice mixed into warm oil: This results in a physical change (the ice melting), and the change can be reversed (the water can refreeze). No new substances are formed.

2. Baking soda mixed into vinegar: This is a classic example of a chemical change. When baking soda (sodium bicarbonate) reacts with vinegar (acetic acid), it produces carbon dioxide gas (which appears as bubbles), water, and sodium acetate. This reaction creates new substances, thus indicating a chemical change.

3. Sugar mixed into hot water: This is a physical change, as the sugar dissolves in the water. The sugar retains its chemical identity, and the process is reversible (the sugar can be recovered by evaporating the water).

4. Sand mixed into water: This is also a physical change. The sand does not dissolve in water, and it can be separated back out. The mixture is still composed of the original substances, with no new substances formed.

Therefore, baking soda mixed into vinegar is a clear example of a chemical change due to the production of new substances (the bubbles from carbon dioxide).