Nguyên tố X có hai đồng vị, đồng vị thứ nhất có số khối 35 chiếm 75%. Nguyên tử khối trung bình của X là 35,5. Đồng vị thứ hai có số khối là A. 36. B. 37. C. 38. D. 39.

Describe the difference between a. a hypothesis and a theory and b. an observation and an experiment.

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?

Which are forms of frozen water? check all that apply. dew frost hail rain sleet