Which of these is an indication that a chemical reaction has occurred?

a. melting of a substance
b. a change of color in a substance
c. boiling of a substance
d. freezing of a substance

Calculate the molar mass of aluminum oxide (al2o3). express your answer to four significant figures.

Which change in temperature is the smallest? a change of 1 thomson degree a change of 1 kelvin degree a change of 1 fahrenheit degree a change of 1 celsius degree

Oil rich countries in the middle east cover about 4% of earths total land area but prossess about 48% of the worlds known oil reserves what is the main reason for high concentration of reserves in this part of the world