Which of the following describes a mixture? a. formed from two or more substances chemically combined

b. can be separated only by chemical means

c. made up of two or more substances that keep their identities

d. made up of two or more substances joined in a specific ratio

Which process does not require the presence of a physical substance in order to transfer heat? air in the atmosphere is heated by the ground. this warm air then rises, and cooler air falls. this is an example of what type of process? how is conduction different from radiation?

Which of the following is an example of physical change not a chemical change? a) a log gives off heat and light as it burns. b) a tree stores energy from the sun in its fruit. c) a penny lost in the grass slowly changes color. d) a water pipe freezes and cracks on a cold night.

Which three statements represent the benefits of performing experiments using computer simulations?