My teacher provided info about a worksheet of problems.
Special Heat of water: 4.184
Special Heat of Steam: 2.09
Special Heat of Ice: 1.8
Based on this info, and the notes we have taken on phase changes, we are supposed to find out how much energy is needed to change certain substances.
I thought, however, that in order to create a phase change, one must use the q=m,delta,Hfusion or m,delta,Hvap. How can I perform these equations without the Hvap/fusion info provided?!
Question 4, for example asks...
...60g of water at 43 degrees celcius to steam at 140 degrees celcius.
Help please?!?!?
q1 = heat to move T of water from 43 C to 100 = mass x speicif heat liquid water x (
Tf - Ti). Tf is final T (in this case 100 and Ti is initial T (in this case 43 C.)
Then you DO, definitely, need the delta H vap for water.
q2 = heat to evaporate water = mass x delta Hvap
q3 = heat to move T of steam from 100 C to 140 C = mass x specific heat steam x (Tf - Ti) =
The total is q1 + q2 + q3.
Judging from your post, I think you knew all of this. You will need to either look up delta Hvap or ask your teacher tomorrow. By the way, note the correct spelling of Celsius.
To solve the problem of finding out how much energy is needed to change substances without provided values for the heat of fusion (Hfusion) or the heat of vaporization (Hvap), you can use the specific heat capacities and the equation q = m × C × ΔT.
In this case, you have the specific heat of water, which is 4.184 J/g°C. The specific heat capacity (C) represents the amount of heat energy required to raise the temperature of 1 gram of a substance by 1 degree Celsius.
However, because you are dealing with a phase change from water to steam, it is important to consider both the change in temperature and the energy required for the phase change.
Let's break down the problem by different stages:
1. Heating the water from 43°C to 100°C:
The specific heat capacity of water (C) is given as 4.184 J/g°C.
The mass of water (m) is 60 grams.
The change in temperature (ΔT) is the final temperature minus the initial temperature: 100°C - 43°C = 57°C.
Use the equation q = m × C × ΔT to find the energy required to heat the water:
q1 = 60 g × 4.184 J/g°C × 57°C
2. Changing the water at 100°C to steam at 100°C:
This represents the heat of vaporization (Hvap) since it involves a phase change. We don't have the specific value for Hvap, but we can assume it to be the same as the heat of vaporization for water, which is 2.09 J/g.
The mass of water (m) is still 60 grams.
Use the equation q = m × Hvap to find the energy required for vaporization:
q2 = 60 g × 2.09 J/g
3. Heating the steam from 100°C to 140°C:
The specific heat capacity of steam is not provided, but you can assume it to be the same as the specific heat of water, which is 4.184 J/g°C.
The mass (m) is still 60 grams.
The change in temperature (ΔT) is 140°C - 100°C = 40°C.
Use the equation q = m × C × ΔT to find the energy required to heat the steam:
q3 = 60 g × 4.184 J/g°C × 40°C
To find the total energy required for the entire process, you need to sum up the energies from each stage:
Total energy = q1 + q2 + q3
By substituting the values into these equations, you can calculate the amount of energy needed to change the water from 43°C to steam at 140°C.