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chemistry
biology
100
What is a substance that has a pH of less than 7?
What is an acid
100
the green substance in the cells of plants that helps the plant undergo photosynthesis
What is chlorophyll?
200
The amount of mass in a given volume
What is density
200
a muscular-walled vessel that distributes blood to the body tissues
What is an artery?
300
a process in which the molecular composition of one or more substances is altered
What is a chemical reaction
300
a substance secreted into the blood by an endocrine gland
What is a hormone?
400
an atom that has acquired a positive or negative charge by losing or gaining electrons
What is an ion
500
the spontaneous breakdown of an unstable atomic nucleus, releasing energetic rays and particles
What is radioactivity?