Question

In the graph, “ppm” stands for parts per million. A concentration of one ppm is a ratio of one part to one million parts. Concentrations can also be expressed as a percentage. Why do you believe scientists choose ppm over percentage in some cases?

Answer 1

Answer: very small amounts are easier to express as ppm.

Explanation: 1 ppm = 0.0001 %

Answer 2

Concentrations like the ones shown in the graph are relatively small. Writing them as percentages would require decimal points and many leading zeros. Therefore, scientists choose ppm over percentages to show CO2 concentrations.

Step-by-step explanation:

This is the exact answer from PLATO so maybe change the wording a little.