To freeze/melt a substance, does the substance have to absorb it release heat?

If a planet rotates 360 degrees during a 24 hour time period, what does that tell us about the planet? a. the middle of the planet is in darkness b. the seasons on the planet vary every day. c. the planet runs on a 12-hour time clock. d. the temperature on the planet varies daily.

Two things that biomedical has invented or innovated

What are the primary responsibilities of a chemical engineer involved in "r& d"? develop large scale manufacturing operations discover new products and processes training of new chemists determine products needed by consumers