Explain ray diagram and derive first law of reflection from that.

What happens to energy in an open system?

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.

How many molecules are in 6.0 moles of methane