Which procedure did early chemists use to determine which substances were elements? a. they observed the substances that made up individual atoms. b. they physically broke down the elements they discovered. c. they broke down materials by chemical means. d. they observed the way the materials looked.

The twister and runaway train are two coasters at the same amusement park. both coasters start at the same height. the coaster for the twister is twice the mass of the coaster for the runaway train. which roller coaster has greater gravitational potential energy at the start of the ride?

Which of these is an example of pseudoscience? a) predicting the time of sunrise based on data on position of earth b) predicting the date of the moon phases based on data on position of earth c) predicting eclipses based on the position of the sun and the moon d) predicting future events in a person's life based on the position of the moon

How many more valence electrons does sodium need to have a full outer valence shell