Classify each of the following as a physical change or chemical change. give reasons for the answers:
a) metallic lustre
b) boiling point
c) explodes when ignited
d)changes colour when mixed with water

Agas diffuses 1/7 times faster than hydrogen gas (h2). what is the molar mass of the gas? 100.10 g/mol 98.78 g/mol 86.68 g/mol 79.98 g/mol

Astudent is trying to create a table that compares hypotheses, theories, and laws. hypothesis theory law do scientific researchers formulate it? yes yes yes does it explain why things happen? yes yes no yes yes yes is it used to make predictions? no yes yes which of the following questions would most likely fill the blank in the table? is it an intelligent guess? is it newly formulated? is it based on observations? has it been proved?

Which of these features are formed when hot groundwater is forced out through cracks in the earth's surface?