NO FILES PLZ HELP!! Which observation does not indicate that a chemical has occurred

A. formation of a precipitate
B. production of gas
C. evolution of heat and light
D. change in total mass of reactants and products

The pressure inside a hydrogen-filled container was 2.10 atm at 21 ? c. what would the pressure be if the container was heated to 92 ? c ?

Both josef loschmidt and amedeo avogadro contributed to our understanding of basic molecular numbers, sizes, and reaction ratios. neither scientist discovered “avogadro’s number” in the form we use it today (6.02 x 10 23). still, there’s a controversy over the name. research the contributions from these two scientists and read about how avogadro’s number got its name. briefly state what you think this number should be called, providing key details of each scientist’s contributions to this concept and a solid rationale for your case in naming the number.

Which best explains why an iceberg floats?