What is the central equation of mass-energy equivalence?

Heat from the sun reaches earth to a. radiation b. convection c. conduction

The speed of sound in ice, water, and steam is shown. what best explains the speed of sound in different states of matter? sound travels fastest in ice because energy is easier to transfer when the molecules are close together. sound travels slowest in steam because the sound has to move around the gas molecules that are far apart. sound travels fastest in ice because the temperature of solids is always greater, so the heat transfers the sound energy. sound travels slowest in steam because the pressure is so great the sound cannot travel though the steam particles.

Glass has a hardness that is in the middle of the hardness scale. what is the hardness of glass?