1. To convert Celsius reading to Kelvin: K = C + 273.15
QUESTION:
During a chemical reaction, the temperature of a mixture dropped by 10.0oC. By how much did the temperature drop in Kelvin.?
A. 10.0K B K, C K
To convert Celsius reading to Kelvin:
K = C
But question deals with change or difference in reading.
K1 = C
K2 = C
(K2-K1) = C2-C1
K = C = 10.0
During a chemical reaction, the temperature of a mixture dropped by 10.0oC. By how much did the temperature drop in Kelvin.?
A. 10.0K B K, C K
PAUSE
CLICK
To convert temperature readings from Celsius to Kelvin,
CLICK we simply add to the celsius reading
CLICK However, this question deals with a temperature change. The question changes, that the temperature dropped
HIGHLIGHT “dropped” in question
by 10.0 degrees Celsius. The conversion formula is different in this case. Let’s see why.
Suppose we start with a Celsius reading of C1. The corresponding Kelvin temperature, K1, ...
is C1 plus Similarly, the Kelvin temperature corresponding to a celsius reading of C2 CLICK is K2, which is equal to C2 plus
Now, let’s take the difference:
K2 minus K1 equals C2 minus C1.
Note that cancels out when you take a difference between two temperature readings.
It is customary to represent changes in quantities using the Greek letter delta.
CLICK So, we can say that the change in the Kelvin reading,... delta K
HIGHLIGHT K
is simply equal to the change in the celsius reading...
HIGHILIGHT C
IN other words, a degree change on the celsius scale corresponds to a change of one kelvin.
CLICK Therefore, the correct answer is A. A ten degree change on the celsius scale corresponds to a 10 Kelvin change.
Note that we do not say degrees when expressing temperatures in Kelvin. We don’t say 10 degrees Kelvin,... we just say 10 Kelvin.
CONTINUED ON NEXT SLIDE

2. C K
40-30 = 10
= 10
Confused?....
Consider the figure shown here which puts the Celsius and Kelvin scales side-by-side.
Note that 0 degrees celsius corresponds to kelvin.
CLICK
And that 10 degrees celsius corresponds to kelvin.
A change of 10 degrees celsius corresponds to a change of 10 Kelvin. From to , the change is 10.
Let’s see what happens when the temperature drops from, say, 40 degrees celsius,
CLICK ...to 30 degrees celsius
CLICK In this case, we’re looking a drop of 10 degrees celsius, minus 30 is 10.
CLICK and a corresponding drop of 10 kelvin minus equals 10.
CLICK PAUSE END RECORDING

3. Video ID: 1A-7-2 © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08