If a chemical reaction occurs in a flask, and the flask becomes colder, the reaction was exothermic. true or false

false

Explanation:

hope this helps you

False, if the flask becomes colder it's endothermic. I hope this helps! :)

indicate valleys, hills, steepness and gentleness of slopes.

explanation:

contour lines on a map indicate elevation, or depth. numeric notations on contour lines refer to the level of elevation, or height about sea level.