Question

A student is investigating some of the properties of eggs through a series of experiments. She records her results in a table, but she is not sure which changes are physical and which are chemical.



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Based on the information in the table, which experiment(s) caused chemical changes and how do you know?



A.
All of the experiments caused chemical changes because they were all irreversible and changed the appearance of the eggs.

B.
Experiments 2, 3, and 4 caused chemical changes, because they changed the basic properties of the eggs; Experiment 1 did not, because it only created a mixture.

C.
Experiments 3 and 4 caused chemical changes, because they involved heat and resulted in new substances; Experiments 1 and 2 did not, because they only created mixtures.

D.
Experiment 4 caused a chemical change, because it created a new, crusty brown substance; the others did not, because they only caused changes in phase and color without changing the chemical makeup of the eggs.

Answer 1

B.

Reason: chemical changes produce new substances or involve chemical reactions and are usually irreversible. In the table the results of Experiments 2–4 show signs of chemical reactions (e.g. reaction with acid or irreversible changes on heating such as protein denaturation/browning), whereas Experiment 1 only formed a mixture/physical change (no new substance formed and it was reversible).