How much heat (in Joules) is needed to raise the temperature from -79oC to 57oC for 31.5g of water?
I remember my teacher using different temperatures for each equation, can someone show me what that is? thanks.
Most likely the teacher was using Kelvin which is 273+C.
No she was doing like for the first equation for temp = (0-(-79)) and for the second equation for temp = (100-57) or something.
If she was trying to find the change in temperature it would be 79+57 =136 is the temperature change.
This is a bit more complicated that it appears. First you must realize that at -79 C, the H2O is in the form of ice. So heat must be added to raise T to zero C, heat added to melt the ice, and finally heat added to raise T from zero C to 57 C.
heat to raise T from -79 C to zero C is
q1 = mass ice x specific heat ice x (Tfinal-Tinitial) where Tfinal is zero C and Tinitial is -79 C.
q2 = heat to melt ice.
q2 = mass ice x heat fusion
q3 = heat to raise T from zero C t 57 C.
q3 = mass H2O x specific heat H2O x Tfinal-Tinitial) where Tfinal is 57 and Tinitial is zero C.
Then total Q = q1 + q2 + q3.
To calculate the amount of heat needed to raise the temperature of a substance, you can use the specific heat capacity formula:
Q = m * c * ΔT
Where:
Q is the amount of heat required (in Joules)
m is the mass of the substance (in grams)
c is the specific heat capacity of the substance
ΔT is the change in temperature (in Celsius)
For water, the specific heat capacity (c) is approximately 4.18 J/g°C.
In this case, you are given:
m = 31.5g (mass of water)
ΔT = (57°C - (-79°C)) = 136°C (change in temperature)
Now you can plug in the values into the formula:
Q = 31.5g * 4.18 J/g°C * 136°C
To calculate this, you need to multiply the mass of water (31.5g) by the specific heat capacity of water (4.18 J/g°C), and then multiply by the change in temperature (136°C).
Q = 17775.12 J
So, the amount of heat needed to raise the temperature of 31.5g of water from -79°C to 57°C is approximately 17775.12 Joules.
Regarding your teacher using different temperatures for each equation, it might be referring to different temperature ranges or scenarios for specific heat. There are different values of specific heat capacity depending on the temperature range or phase changes (such as solid, liquid, or gas). However, for this specific question, we are using the specific heat capacity of water throughout the temperature change.