Question

A graduate student adds 100J of energy to a sample of ethanol at a temperature below the boiling point. The addition of energy causes no change in temperature. What explains this observation.

A more energy necessary to change temp
B the sample is at the melting point
C the bond energies are all greater than 100 J so the bonds could be broken.
D the energy dissipates as friction.

Answer 1

I feel like it's between A/D

Answer 2

I'm thinking this one could be A

Answer 3

C doesn't make sense as it says bonds are broken normally when the bond breaks energy is released in the form of heat so it should change the temperature

Answer 4

Sample is at it's melting point? that doesn't even apply because ethanol is a liquid at RT.

Answer 5

Why are you thinking D?

Answer 6

no... wait... it's below the boiling point. maybe that energy was not enough to cause a change in temperature...

yeah.. friction? maybe don't know considering collisions aren't elastic some of that energy would be lost to friction. wasn't sure.. I think A makes more sense.

Answer 7

but if D.. were the case that would always be the case..

Answer 8

Friction normally causes some sort of heat to form thus changing the temperature doesn't it

Answer 9

explain that? energy is lost to friction so wouldn't that not raise the temperature by that much?

Answer 10

Is it A?

Answer 11

The question itself says the answer right?

Answer 12

tara

Answer 13

Normally when it hits the boiling point it's changing phases so then it would require a change in temperature but in order for it to change phases you need the energy to overcome the forces involved so if it didn't have enough energy the temperature wouldn't have changed

Answer 14

... it's B..

Answer 15

let me write the explanation

Answer 16

"the only time you add energy to a sample and have the temperature remain constant is when there is a phase change. the problem states that ethanol is at a temperature below its boiling point, the only other phase transition would be melting"

Answer 17

to me this was a bad way of testing this concept.. because first of all ethanol is a liquid at room temperature.. and it's at a temperature below the boiling point. okay yeah like I knew that phase transitions were an (equlibirum process) where the temperature remains relatively constant.

Answer 18

but the way they asked it was just dumb to me...

Answer 19

It doesn't say specifically at room temperature so that's why it wouldn't nessicarilly be a liquid and this question definitely could have been asked better

Answer 20

yeah.. true.. I guess i shouldn't have assumed that.. but to me this is stupid because melting implies that it's a solid.. I guess we were supposed to assume that..

Answer 21

I will post more.

Answer 22

I like how we are told in classes to make assumptions so we automatically get trained to assume parts of questions and that ruins it in some questions