Radioactive isotope has a half-life of 1.2 billion years. as measured by the presence of the isotope and its stable decay product, a rock originally contained 10 grams of the radioactive isotope, and now contains 1.25 grams. approximately how many years old is the rock?

Which statement describes how phase changes can be diagrammed as a substance is heated? the phase is on the y-axis and the temperature is on the x-axis. the temperature is on the y-axis and the phase is on the x-axis. the time is on the y-axis and the temperature is on the x-axis. the temperature is on the y-axis and the time is on the x-axis.

Compare and contrast physical changes with chemical changes.

Chemistry worksheet - i am not sure what they are asking for exactly?