How Do I Calculate Energy Changes in Thermodynamics Problems?

  • Thread starter Thread starter Roro312
  • Start date Start date
  • Tags Tags
    Test
AI Thread Summary
To calculate energy changes in thermodynamics problems, start by determining the energy required for phase changes and temperature increases. For the ice cube, first convert it from solid to liquid using the formula E = mLf, then raise the temperature to the boiling point, and finally convert the liquid to vapor using E = mLv. In the case of the mandarin orange, calculate the energy needed to raise the temperature of the water using Q = mc(Tf - Ti), where m is the mass of the water and c is the specific heat capacity. Combine all calculated energies to find the total energy for each problem. Understanding these formulas is crucial for solving thermodynamics questions effectively.
Roro312
Messages
12
Reaction score
0
Tomorrow is my test and i understand partially everything... and than i stumbled upon these two questions and if i just know what's used for each formula .. i can do it

1) Calculate the amount of energy required to evaporate an ice cube having a mass of 45g.

I know that first it must go for solid to liquid which is E=mf and than from liquid to gas which is E=mLv .. can someone please show me how to do them... my test is tomorrow:(

Lf water= 3.3x10^5 J/Kg
water=4.2x10^3 J/Kg'C
ice= 2.1x 10^3 J/Kg'C

the other question i didnt get was:

2)An 80g mandarin orange is burned in bomb calorimeter. The 1.55 kg of water change in temperature from 21.0'C to 39.4'C. Calculate the energy per gram in the mandarin orange.


I would show you my attempt except its just ridiculous becuase i reallyyyy don't get it.


Your help is muchhhh appreciated.. i need help ASAP ...thank you
 
Physics news on Phys.org
Well for the first one, you will need energy to

1)convert the ice to liquid which is (solid to liquid)
2) Raise the temperature to the boiling point of water
3) convert all the liquid to vapor

So find the individual energy requirements and add them up.


For the second one, how much energy would it take to raise the temperature of water of mass 1.55kg from 21C ro 39.4C?.
 
Thats the problem... i don't know how to convert solid to liquid.. what formula do i use?
 
Q=mC C is a constant you can look up for water its different depending on which phase transition you are calculating.
Q=mc(Tf-Ti) for when your raising the temperature c i think its 1cal/gC for water.

Add all the Qs and viola
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

I try to solve a thermodynamics problem on heat transfer
Replies
3
Views
2K
Calculate the Mass of Ice cubes needed to cool a soft drink
Replies
10
Views
3K
How much water is converted to ice?
Replies
1
Views
3K
Entropy change as water is frozen
Replies
2
Views
5K
How Does Energy Transfer Affect Entropy in a Water-Ice System?
Replies
3
Views
2K
How Do You Calculate Heat Transfer in a Thermodynamics Piston Problem?
Replies
5
Views
3K
Calculating Heat Energy Changes in a Water and Ice System
Replies
6
Views
2K
Thermodynamics internal energy Problem
Replies
1
Views
2K
Calculating Energy Required to Heat and Change State of Ice in an Oven
Replies
12
Views
3K
How Do You Calculate Entropy Change When Melting Ice at Varying Temperatures?
Replies
1
Views
16K

Hot Threads

Recent Insights

Back
Top