Which of there is an indication that a chemical reaction has occurred?
a. freezing of substance
b. a change in color of a substance
c. melting of a substance
d. boiling of a substance

Using the periodic table, complete the table to describe each atom. type in your answers.a ? b? c? d? e? f?

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

Great amounts of electromagnetic energy from our sun and other bodies in space travel through space. which is a logical conclusion about these electromagnetic waves? their energy must be very their frequency must be very low these waves can travel without a medium they only travel through a vacuum of space