Chapter 2

Question 1

all matter is composed of … naturally occurring elements

Answer 1

92

Question 2

six elements make up … of the body weight of organisms. These are: …, …, …, …, …, and … (CHNOPS)

Answer 2

95%; carbon; hydrogen; nitrogen; oxygen; phosphorus; sulfur

Question 3

because the chemical behavior of a radioactive isotope is the same as a … of a particular element, low levels of the radioactive isotope allow researchers to … the … and … of the element in …, these isotopes are called …

Answer 3

stable isotope; trace; location; activity; living tissues; tracers

Question 4

high levels of radiation can .. and cause …, careful use of radiation can … and kill …

Answer 4

destroy cells; cancer; sterilize products; cancer cells

Question 5

when atoms absorb energy during photosynthesis, electrons are boosted to … when they return, the released energy is converted into … which supports all life

Answer 5

higher energy levels; chemical energy

Question 6

electrons possess …, and bonds that exist between atoms in molecules therefore contain …

Answer 6

energy; energy

Question 7

below …, hydrogen bonding becomes more … but more …, causing ..

Answer 7

4 degrees C; rigid; open; expansion

Question 8

positron-emission tomography (PET) can be used to determine … of …

Answer 8

comparative activity; tissues