Why is ice melting considered to be a PHYSICAL change? A. the water molecules do not change chemically and are still H2O
B. the water molecules change into new chemicals and are no longer H2O
C. They are chemically mixed and won’t for H2O
D. They will just be the same liquid (already did this and it wasn’t it)

How has the scientific community addressed the safety of chemicals? a. chemicals are repeatedly tested, even those that have existed for a long time. b. existing chemicals are tested if they have never been tested before. c. chemicals are tested if they are suspected to have caused a problem. d. only new chemicals are tested.

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 of the dna typing techniques do you think you would choose if you had to analyze a dna sample? why?