Which action describes a chemical change? A.) Crushing Rock

B.) Lighting a Match

C.) Freezing Water

D.) Melting Ice

B

Explanation:

a chemical change is something that can not be reversed, so you may think crushing a rock but it isn't because crushing a rock is a phisical change not chemical and if you freeze water you can melt it and of you melt ice you can freeze it, so those can be reversed. So the answer is B because that can not be reversed

in scientific notation, the value of the  speed of light in a vacuum

  will be written as 2.995 * 10^8. when this value is represented in the form of

  a * 10^b, then, a = 2.995 and b = 8.

the value of the speed of light in a vacuum given above can also be rounded up to approximately 300000000. in this case, the scientific notation will be written as 3 *10^8.