Achieve homework question #3

[Xinyue Zou 2K]

Hello!
I was wondering if someone could clarify and explain why the reactions on our Achieve homework #3 are classified the way they are as endothermic or exothermic.
Thank you!

Classify the processes as endothermic or exothermic:
The chemical reaction inside an instant cold pack
baking a cake
ic melting
water condensing on a surface
a car using gasoline

[lily_oneal_2B]

Endothermic reactions take energy from surroundings and absorb it. Exothermic reactions release energy to the surroundings. That being said

chem rxn in a cold pack- endothermic because it absorbs heat to the inside of the pack to make the outside cold
baking a cake-endothermic as the batter absorbs heat from the oven
ice melting- ice absorbs heat from surroundings to change to liquid
water condensing on surface- exothermic, water goes from gas to liquid, so it releases heat
car using gasoline- exothermic, gas releases heat, which is used as work to power the car

[Caroline 2A]

Hi!

Endothermic or exothermic reactions are dependent on the flow of energy between the system and its surroundings. Endothermic processes are reactions that absorb the energy from its surroundings, sometimes causing its surroundings to get cooler. Exothermic processes are reactions that expel the energy to its surroundings, sometimes causing the surroundings to get warmer.

Hope this helps :)

[Irene Kim 3E]

For this question, we just need to consider is whether the reaction requires heat (endothermic) or releases heat (exothermic). For example, ice melting requires heat and thus is an endothermic reaction. Another way to think about it is that it implies a phase change from solid to liquid; reactions that change solid -> liquid, liquid -> gas, or solid -> gas are all endothermic processes.

[Lily Rivas 1H]

Knowing the molecules move more freely as they move to a "higher state" a.k.a solid --> liquid --> gas and knowing that entropy increases as microstates increase, Moving up this ladder will give us a positive entropy. If we move our way down this state ladder we have a negative entropy as we decrease the number of microstates possible. Less microstates = less free movement of molecules.

[605499821]

We just determine whether or not the reaction requires heat or is giving off heat. When ice cream melts this is considered endothermic because it requires heat to melt vs. freezing water which is considered exothermic because it is releasing heat.

[Daniela G 2C]

Endothermic processes are ones that absorb energy while Exothermic are ones that release energy. For example, baking a cake is endothermic because heat is required and the process absorbs the heat ( to bake) while water condensing on a surface is an exothermic process because it releases energy to phase change (going from a gas to liquid).