Nucleosynthesis began when and ended when

A. the Big Bang occurred; the Big Crunch occurred

B. nuclear reactions could first occur; matter had condensed into galaxies and stars C. the cosmic microwave background radiation formed; dark energy replaced it as the dominant energy form

D. the universe had cooled enough for atoms to combine; protons and neutrons were too far apart to form nuclei

Agroup of students is studying convection currents. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other in an area with warm air. after 10 minutes, the balloons are released from a height of 1 meter. which of the following do the students most likely observe? a. the balloons both rise. the cold balloon is larger than the warm balloon. b. the balloons rise at the same rate. both balloons are the same size. c. the warm balloon expands and rises. the cold balloon shrinks and sinks. d. the cold balloon expands and rises. the warm balloon shrinks and sinks.

Which type of substance ionizes partially and gives off hydrogen ions when dissolved in water? a. strong acid b. strong base c. weak acid d. weak base

Draw the skeletal structures of two different molecules that are each made of 5 carbon atoms and 12 hydrogen atoms.