What phase change requires a substance to absorb energy? select all that apply. melting freezing evaporation sublimation condensation

When a solid is converted to a liquid, energy must be absorbed. This process is termed as melting.

The reverse process of melting is freezing, where liquid fuses to form a solid. Energy is released in this process.

Evaporation is the conversion of liquid to vapor by absorbing energy.

Sublimation is the direct conversion of solid to vapor state by absorbing energy.

Condensation is the reverse of evaporation. In condensation vapors condense to form liquid releasing energy in the process.

Therefore, the processes that absorb energy are melting, evaporation and sublimation.

1. the question asks the most appropriate, which seems to rule out "all of the above." your choice appears to be the correct one.

2. the protocol described is good for identifying correlation, but not cause and effect. for cause/effect, you need to devise a protocol that will assign the treatment (or not) to groups that have essentially the same "demographics" with respect to all the other variables. your choice regarding control group seems appropriate. random assignment of treatment (choice d) may be appropriate also. (i think you can argue that b and d are just different descriptions of the same method.)

3. d will randomize the birds, but may not guarantee there are 10 in each group. e will do both, so seems the better choice.

comment on question 2

based on the problem statement, it seems clear that confident, attentive drivers are more likely to use daytime running lights. so, the protocol might need to be devised in such a way that the lights would be turned on or off without the driver's knowledge. (an attentive driver will figure it out.) assigning a confident, attentive driver to a group required to drive without running lights might mess with his/her confidence and attentiveness. you don't want your experiment to do that. (nor do you want the experiment to subject a driver to greater risk of accident as a consequence of driving without running lights.) experiments involving human safety are always problematic.

0.88m hope i am correct : )