A substance must be... A. a heterogeneous mixture

B. an element or compound

C. a homogeneous mixture

D. an element

Which of the following is a testable hypothesis? a. if i brush my teeth, i will get fewer cavities than if i don't brush my teeth. b. green toothpaste tastes better than blue toothpaste or red toothpaste. c. smart, careful, healthy people always brush their teeth. d. it's wrong to not brush your teeth before you have an important conversation with someone.

What are the 4 phases of matter in order of increasing engery content?

Apiece of metal with a length of 1.42 cm was measured using four different instruments. which of the following measurements is the most accurate?