True or False? A change in color is evidence of a chemical reaction

Describe the forces both attractive and repulsive that occur as two atoms move closer together.

Consider a culture medium on which only gram-positive organisms such as staphylococcus aureus colonies can grow due to an elevated nacl level. a yellow halo surrounds the growth, indicating the bacterium fermented a sugar in the medium, decreasing the ph as a result and changing the color of a ph indicator chemical. this type of medium would be referred to as a differential and enrichment culture.

Which diagram represents the phase tha occurs after a solid melts?