The amount of space is ___ and a common unit is ___. A. mass, gram
B. volume, gram
C. mass, mL
D. volume, mL

Two friends at different locations want to communicate with each other by sending low energy signals. which of the following methods can they use to communicate? a) produce x-rays using colliding electrons and send them to radios, which capture sound b) send messages using infrared radiation, which travel in the form of waves c) send radio waves through intervening media like radio and television d) produce sound waves using microwaves from heated objects

Describe the difference between a. a hypothesis and a theory and b. an observation and an experiment.

The volume of an unknown substance in a sealed glass jar is 50 milliliters. the volume of the jar is 200 milliliters. which state of matter could the substance be?