What is the percentage by mass of fluorine in sulfur hexafluoride?

An observation that requires measurement is called quantitative observable or qualitative

How do you lengthen a pattern piece? (family and consumer science, sewing)

Which statement is true about a catalyst? a: a catalyst decreases the rate of the reaction. b. a catalyst is consumed during a chemical reaction. c. a catalyst lowers the activation energy of a reaction. d. a catalyst increases the reactant concentration during a reaction.