Pure sodium metal explodes when it makes contact with water, and chlorine, in its natural state, is a deadly, poisonous gas. When these two chemicals combine, they form a harmless, white powder known as sodium chloride or table salt. Which of the following statements does this information support? A. The properties of substances change during chemical reactions but then later go back to their original condition.

B. Heat must be added in order to change the chemical properties of substances.

C. When substances are chemically combined, the properties of the new substances that are formed are often different from the properties of the original substances.

D. When substances are chemically combined, the properties of the new substances that are formed are the same as the properties of the original substances.

An internally reversible refrigerator has a modified coefficient of performance accounting for realistic heat transfer processes of where qin is the refrigerator cooling rate, qout is the heat rejection rate, and is the power input. show that copm can be expressed in terms of the reservoir temperatures tc and th, the cold and hot thermal resistances rt,c and rt,h, and qin, as where rtot rt,c rt,h. also, show that the power input may be expressed as 1.39 a household refrigerator operates with cold- and hot-temperature reservoirs of tc 5 c and th 25 c, respectively. when new, the cold and hot side resistances are rc,n 0.05 k/w and rh,n 0.04 k/w, respectively. over time, dust accumulates on the refrigerator’s condenser coil, which is located behind the refrigerator, increasing the hot side resistance to rh,d 0.1 k/w. it is desired to have a refrigerator cooling rate of qin 750 w. using the results of problem 1.38, determine the modified coefficient of performance and the required power input w under (a) clean and (b) dusty coil conditions. internally reversible refrigerator qout qin w high-temperature reservoir low-temperature reservoir th th,i tc,i tc high-temperature side resistance low-temperature side resistance w qin th tc qinrtot tc qinrtot copm tc qinrtot th tc

Aphysical change is a change in the size, shape,, or stafe of matter true or false

If steel is more dense that lake water, why can a boat float