19. Classify the chemical reaction photosynthesis as ender- gonic or exergonic. Explain.
20. Explain why the total amount of energy does not decrease in an
exergonic chemical reaction.
3 21. Explain How can an endergonic reaction not be endothermic?
22. Classify the reaction that makes a firefly glow in terms of energy
input and output.
23. Think Critically To develop a product that warms people's hand
would you use an exothermic or endothermic reaction? Why?

1. what is the relationship between wavelength and the penetrating power of an electromagnetic wave? a) the penetrating power has no relationship to the wavelength. b) the penetrating power increases as the wavelength increases. c) the penetrating power decreases as the wavelength increases. d) the penetrating power decreases as the wavelength decreases. 2. as ice melts and turns into water, the speed of sound through the material would most likely do what? justify your answer. a) the speed would not change because the material is always water. b) the speed of sound would increase because the density of water is less than that of ice. c) the speed of sound would increase because energy is added to ice in order to make it melt. d) the speed of sound would decrease because sound travels faster through solids than liquids. 3.which of these waves need a medium to travel through? a) sound b) x-rays c) infrared rays d) visible light