Which sample of matter is a mixture?

What is the independent variable in this investigation? mass volume sample number substance density

1) which of the following is the best example of a physical change? a) sugar dissolving in tea b) firefly glowing 2) in the combustion of ethane, what is/are the reactants? c2h6 + o2 ==> co2 + h2o a) c2h6 and o2 b) co2 and c2h6

Which of the following would not diffuse through the plasma membrane by means of simple diffusion? 1 oxygen 2 glucose 3 a steroid hormone 4 a lipid soluble vitamin