What is a solution? a. one substance dissolved in another substance b. a pure substance by itself c. one liquid layered on another liquid d. two substances chemically bonded together

30 points - when can a theory be modified if a new type of technology allows for new observations that raise new questions? a. immediately, while the questions about the theory are being asked b. after new hypotheses related to the theory are tested in experiments c. only after the new observations disprove all parts of the theory d. while scientists begin to think about how the theory could improve

If an athlete runs once around a track, back to the starting line, her average velocity is zero. true or false?

Which of the following is not a physical property of mattera. melting pointb. heat of combustionc. viscosityd. boiling point