| Saat Shade Purmando
What happens when you heat a solid? Heating a substance Increases its thermal energy.
When the partides in a solid have more thermal energy, they vibrate more quickly, and the
temperature of the substance goes up. Once the substance reaches a certain temperature,
called its melting point, the substance can begin to change state.
As more thermal energy is added to the substance, its partides gain enough thermal energy
to move around more freely. The partides remain close together, but they are able to slide
past one another. When all of the particles have broken out of their fixed positions, the
substance has changed state.
solid
liquid
Which of the following happen during this change of state? Select all that apply.
The number of particles in the substance increases.
The parties in the substance move far apart.
The substance melts and becomes a liquid
Sat

A3-mm-thick panel of aluminum alloy (k 177 w/m-k, c 875 j/kg-k and ? = 2770 kg/m) is finished on both sides with an epoxy coating that must be cured at or above t,-150°c for at least 5 min. the production line for the curing operation involves two steps: (1) heating in a large oven with air at ts,0-175°c and a convection coefficient of h, 40 w/m2. k, and (2) cooling in a large chamber with air at 25°c and a con- vection coefficient of he 10 w/m2.k. the heating portion of the process is conducted over a time interval te which exceeds the ime required to reach 150°c by 5 min (h = r + 300 s). the coating has an emissivity of ? = 0.8, and the temperatures of the oven and chamber walls are 175 and 25°c, respectively. if the panel is placed in the oven at an initial temperature of 25°c and removed from the chamber at a safe-to-touch tempera ture of 37°c, what is the total elapsed time for the two-step curing operation?