During osmosis, the semi-permeable membrane is one that: a. allows only very small particles or water through. b. allows only very large particles through. c. does not allow any particles to pass through. d. decides what particles to let through based on cell signals.

Osmosis always moves a solvent in one direction only, from a less concentrated solution to a more concentrated solution. As osmosis proceeds, pressure builds up on the side of the membrane where volume has increased. Ultimately, this pressure prevents more water from entering.

http://www.indiana.edu/~nimsmsf/P215/p215notes/LabManual/Lab5.pdf

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.

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