Viviana's Chemistry Notebook

Step One: solid ice rises in temperature
As we apply heat, the ice will rise in temperature until it
arrives at its normal melting point of zero Celsius.
Once it arrives at zero, the Δt equals 10.0 °C.
Here is an important point: THE ICE HAS NOT MELTED
YET.
At the end of this step we have SOLID ice at zero
degrees. It has not melted yet. That's an important point.
Each gram of water requires a constant amount of energy
to go up each degree Celsius. This amount of energy is
called specific heat and has the symbol c.
72.0 grams of ice (no liquid water yet!) has changed 10.0 °C. We need to calculate the energy
needed to do this.
This summarizes the information needed:
Δt = 10 °C
The mass = 72.0 g
c = 2.06 Joules per gram-degree Celsius
The calculation needed, using words & symbols is:
q = (mass) (Δt) (c)
Why is this equation the way it is?
Think about one gram going one degree. The ice needs 2.06 J for that. Now go the second degree.
Another 2.06 J. Go the third degree and use another 2.06 J. So one gram going 10 degrees needs
2.06 x 10 = 20.6 J. Now we have 72 grams, so gram #2 also needs 20.6, gram #3 needs 20.6 and so
on until 72 grams.
With the numbers in place, we have:
q = (72.0 g) (10 °C) (2.06 J/g °C)
So we calculate and get 1483.2 J. We won't bother to round off right now since there are four more
calculations to go. Maybe you can see that we will have to do five calculations and then sum them all
up.
One warning before going on: three of the calculations will yield J as the unit on the answer and two
will give kJ. When you add the five values together, you MUST have them all be the same unit.
In the context of this problem, kJ is the preferred unit. You might want to think about what 1483.2 J is
in kJ.
Notes:
- Ice has no melted at 10.0 C
- Solid ice at zero degrees
- Each gram of water requires a constant amount of enrgy to go up each degree Celsuis; also known
as specific heat and has the symbol c
- q = (mass) (delta t) (c); used to calculate the energy
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