Question

A calorimeter is used in an experiment. The initial temperature was found to be 32 degrees Celsius. The final temperature was found to be 15 degrees Celsius. What is the direction of thermal energy flow and the resulting change in enthalpy, if any.

Answer 1

the reaction absorbed energy

Answer 2

how is that so? I would think that since the temperature decreased, energy was released and the change in enthalpy would be negative (it went down 17 degrees Celsius)

Answer 3

the temperature decreased meaning energy was absorbed. it went from 32 to 17 degrees

Answer 4

energy released would mean that the temperature went up, no? if you burn something, does it absorb or release energy?

Answer 5

absorbing energy would make the object hotter...

Answer 6

yes, but the chemical reaction is absorbing the energy which is used for bond making etc

Answer 7

i know it seems odd, but the temperature of the surroundings is going down, meaning the energy is being absorbed by the system.

Answer 8

ohh okay, so the water would be the surroundings? For some reason I was thinking that the water is the object and the air is the surrounding or something. (can you tell I' really bad at chemistry?) lol

Answer 9

the water would be the surrounding and the chemicals in the reaction are the system

Answer 10

ohhh okay i understand

Answer 11

so the change in enthalpy is negative because the temperature decreased right?

Answer 12

no negative change in enthalpy means exothermic, the reaction in this case was endothermic because it decreased the temperature of the surroundings (water).

Answer 13

Okay, so the reaction absorbed heat, meaning it's endothermic, and has a positive change in enthalpy.

Answer 14

yep! because the energy (enthalpy) or the products are higher in energy.

dH=products-reactants

if H(reactants)=5, and H(products)=8

dH=8-5= positive

Answer 15

Awesome, thank you for helping me understand this!

Answer 16

no problem !