How many hydrogen atoms are in 4 molecules of H2O?

Which metal exist in liquid state and can be cut with knife ?

Which process does not require the presence of a physical substance in order to transfer heat? air in the atmosphere is heated by the ground. this warm air then rises, and cooler air falls. this is an example of what type of process? how is conduction different from radiation?

Melissa is interested in her family tree and how her family has changed over its many generations. melissa probably more closely resembles