Which of the following represents a phase change? a. melting b. crushing c. expanding d. burning

Which class of molecules functions as chemical signals? hormones water carbohydrates proteins

Lab reagent, hypothesis test. a reference solution used as a lab reagent is purported to have a concentration of 5 mg/dl. six samples are taken from this solution and the following concentrations are recorded: (5.32, 4.88, 5.10, 4.73, 5.15, 4.75) mg/dl. these six measurements are assumed to be an srs of all possible measurements from solution. they are also assumed to have a standard deviation of 0.2, a normal distributin, and a mean concentration equal to the true concentration of the solution. carry out a significance test to determine whether these six measurements provide reliable evidence that the true concentration of the solution is actually not 5 mg/dl.

Citric acid has a ph between 1 and 3.  it is considered to be aa. weak acidb. weak basec. strong based. strong acid