zarkam21:

Help

3 months ago
zarkam21:

1 attachment
3 months ago
zarkam21:

CH4 & 2o2 = reactants CO2 & 2H2O = products

3 months ago
Vocaloid:

perfect

3 months ago
zarkam21:

How do an endothermic reaction and an exothermic reaction differ? An endothermic reaction means that it's happening inside and an exothermic reaction means it is happening outside.

3 months ago
Vocaloid:

that's actually not quite true, exothermic vs endothermic is defined by the energy difference between reactants/products

3 months ago
Vocaloid:

|dw:1521640953085:dw|

3 months ago
zarkam21:

An exothermic reaction is a chemical reaction that releases more energy than it absorbs. An endothermic reaction is a chemical reaction that absorbs more energy than it releases.

3 months ago
Vocaloid:

exo = releases energy, products have lower energy than reactants endo = absorbs energy, products have higher energy than reactants

3 months ago
Vocaloid:

yeah, that's about right

3 months ago
zarkam21:

1 attachment
3 months ago
zarkam21:

egg would be endo?

3 months ago
Vocaloid:

yes

3 months ago
zarkam21:

photosynthesis = ex burning a candle= endo

3 months ago
Vocaloid:

photosynthesis is actually endothermic (ngl had to look this one up myself) burning something is almost always exothermic

3 months ago
zarkam21:

using an instant cold pack- exo using a chemical hand-warmer-exo car engine-endo

3 months ago
Vocaloid:

combustion (which is involved in the car engine) would be exothermic cold pack - it absorbs heat from the environment so endothermic hand-warmer would be the opposite of a cold pack, it gives off heat so exothermic

3 months ago
zarkam21:

In the space below, draw a potential energy diagram for an endothermic reaction and a second potential energy diagram for an exothermic reaction. Give each graph a title, and label the reactants and products on each graph.

3 months ago
zarkam21:

This woukld basically just be something like what you posted right?

3 months ago
zarkam21:

1 attachment
3 months ago
zarkam21:

This?

3 months ago
Vocaloid:

yes

3 months ago
zarkam21:

1 attachment
3 months ago
zarkam21:

yes no yes for the first one

3 months ago
Vocaloid:

|dw:1521641894356:dw|

3 months ago
Vocaloid:

keep in mind we're just talking about matter for the first row

3 months ago
Vocaloid:

isolated system does not allow either matter or energy so isolated would be no for first row

3 months ago
zarkam21:

so yes yes no

3 months ago
zarkam21:

or yes no no

3 months ago
Vocaloid:

YNN

3 months ago
Vocaloid:

what about row 2?

3 months ago
zarkam21:

For energy it needs to be Yes Yes yes

3 months ago
Vocaloid:

keep in mind an isolated system allows neither energy nor matter

3 months ago
zarkam21:

Yes yes no :p

3 months ago
Vocaloid:

that's correct

3 months ago
zarkam21:

Fill in the blanks in the following paragraph to correctly identify the signs associated with heat and work. When a system is heated, heat is _______________ by the system. The amount of heat added is given a _______________ sign. When a system is cooled, heat is _______________ by the system. The amount of heat is given a _______________ sign. If a gas expands, it must push the surrounding atmosphere away. Thus, work is done _______________ the system and is given a _______________ sign. If a gas is compressed, then work is done _______________ the system. This work is given a _______________ sign.

3 months ago
Vocaloid:

thoughts so far?

3 months ago
zarkam21:

um does it have to do with exothermic and endothermic

3 months ago
zarkam21:

or expanded or extracted

3 months ago
Vocaloid:

for the first blank they're probably looking for something like "absorbed"

3 months ago
Vocaloid:

what about the second blank? positive or negative?

3 months ago
zarkam21:

positive

3 months ago
zarkam21:

actually neg.

3 months ago
Vocaloid:

you had it right the first time, heat absorbed gets a + sign

3 months ago
Vocaloid:

third blank is opposite of absorbed, so released, fourth is the opposite of positive, so negative

3 months ago
Vocaloid:

for "work done by system" do you remember if the sign is + or -?

3 months ago
zarkam21:

positive but work done on the the system is neg

3 months ago
Vocaloid:

the gas is expanding so we say the work is done (by) the system (since we are looking from the perspective of the system, not the person doing work on it) so 5th blank is "by" and 6th is positive

3 months ago
Vocaloid:

last two blanks are just the opposite of those two blanks, so "on" the system and negative sign

3 months ago
zarkam21:

an then work done "on:

3 months ago
zarkam21:

Yup that's what I was going to say

3 months ago
zarkam21:

What is the change in internal energy if 50 J of heat are released from a system, and the system does 80 J of work on its surroundings?

3 months ago
Vocaloid:

the sign convention can be tricky, but if heat is being released what's the sign on heat, and if the system is doing work what's the sign on work?

3 months ago
zarkam21:

the sign convention can be tricky, but if heat is being released what's the sign on heat= pos if the system is doing work what's the sign on work= neg

3 months ago
Vocaloid:

heat is being released from the system, so from the system's perspective it's losing heat work done (by) system is positive so Q = neg, Work = positive so if U = Q - W, U = ?

3 months ago
zarkam21:

-50-80?

3 months ago
Vocaloid:

awesome, so -130J

3 months ago
zarkam21:

a. Fill in the blanks in the following paragraph to correctly identify four principles of the second law of thermodynamics. Heat naturally flows from an object that has a _______________ temperature to an object that has a _______________ temperature. Heat can be made to flow in the reverse direction if _______________ is done. A machine can never have an efficiency of _______________. This means that heat energy can never be fully converted into _______________ energy.

3 months ago
zarkam21:

high temp to low temp?

3 months ago
Vocaloid:

yes for the third blank, any ideas? what has to be done to make heat flow from low to high temp?

3 months ago
zarkam21:

work

3 months ago
Vocaloid:

awesome any ideas for the efficiency question?

3 months ago
zarkam21:

um energy?

3 months ago
Vocaloid:

efficiency is usually given as a percentage, what percentage efficiency would be impossible according to the laws of thermodynamics?

3 months ago
zarkam21:

100

3 months ago
Vocaloid:

good, so 100 percent goes into the blank the last blank I'm actually not 100% sure but a good hunch would be "mechanical" :S

3 months ago
zarkam21:

oh okay, i was leaning towards work but I am just guessing so I will do with mechanical

3 months ago
Vocaloid:

yeah I just double checked and it seems like it would be mechanical since work isn't classified as a type of energy

3 months ago
zarkam21:

perfect

3 months ago
zarkam21:

Describe entropy. What is the natural tendency of the entropy of a system? Entropy is an important concept in physics that uses microscopic aspects to describe the thermodynamics of the systems of molecules. The natural tendency of the entropy of a system is to increase over time.

3 months ago
Vocaloid:

good start, probably should mention that entropy is the number of states/configurations a system can have

3 months ago
zarkam21:

Entropy is an important concept in physics that uses microscopic aspects to describe the thermodynamics of the systems of molecules. It is also the number of the variations of states and/or configurations a system can have. The natural tendency of the entropy of a system is to increase over time.

3 months ago
Vocaloid:

good

3 months ago
zarkam21:

How does a heat engine differ from a heat pump?

3 months ago
zarkam21:

Heat Engine is the system that converts the Heat energy into mechanical work. while Heat pump converts the work into heat. Heat Engine is the system that converts the Heat energy into mechanical work.

3 months ago
Vocaloid:

good (make sure you delete that last sentence since you repeated yourself)

3 months ago
zarkam21:

Im gonna open a new thread this is getting long

3 months ago
Vocaloid:

sure

3 months ago
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