You have performed a serial dilution of an unknown sample and counted 73 cfu on a countable plate that was marked as a 10^-4 dilution and you used a 0-.1 ml to inoculate the plate. what is the population density of the original sample?

Which of the following is an indication that a substance has undergone a chemical change? a. no new product has been formed. b. the color of the substance has not changed. c. the original constitute has not changed. d. the molecular structure has changed.