When hcl(aq) and naoh(aq) are mixed in a beaker, the beaker feels warm to the touch. what is known about the enthalpy of this reaction?

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.