I have this problem from chapter five of the Ktoz, Treichel and Towmnd Chemistry and Chemical Reactivity book, and I doing this with their permission.
denmark是什么意思这是来自Ktoz,treichel and Towmnd合编的《化学与化学反应》第五章的题,经过转载同意。
So they tell us that ethanol C2H5OH, boils at—let me do this at orange—it boils at 78.29 degrees Celsius.
题目说乙醇C2H5OH，让我用橙色标记一下,在78.29℃沸腾。
How much energy, in joules, is required to rai the temperature of 1 kilogram of ethanol from 20 degrees Celsius to the boiling point and the change the liquid to vapor at that temperature?
问需要多少焦耳的能量，能让1千克的乙醇从20℃升温到沸腾,然后从液态蒸发到气态呢
So there’s really two parts of this problem.
所以这个问题分为两部分。
How much energy, in joules, to take the ethanol from 20 degrees to 78.29 degrees Celsius?
首先乙醇从20℃到78.29℃需要多少焦耳的能量？
That’s the first part. And then once we’re there, we are going to have 78.29 degrees Celsius liquid ethanol.
精英培训
这是第一部分.然后这时乙醇应该是78.29℃的液体.
But then we also need the energy to turn it into vapor.
然后我们再求蒸发需要的能量。
So there’s going to be the two parts. So let’s just think about just raising the liquid temperature.
这是第二部分。我们先来看看升温这一部分。
Let’s figure out how we’re going to do that. Just the liquid temperature.
我们来分析一下怎么升高液体的温度
So the first thing I looked at is how many degrees are we raising the temperature?
我首先想到的是温度一共升了多少度？
Well we are going from 20 degrees Celsius—let’s write Celsius there just so it’s clear--20 degrees Celsius to 78.29 degrees Celsius.
呐，是从20，还是把单位写完整比较清楚，是从20℃到78.29℃。
So how much did we rai it? Well 78.29 minus 20 is 58.29.
英语语法顺口溜
那么温度升了多少？呐，78.29-20就是58.29。
So our change in temperature is equal to 58.29 degrees.
所以温度的变化ΔT 是等于58.29度。
And it could actually be 58.29 degrees Celsius or this could even be 58.29 kelvin.
这既可以是58.29℃,也可以是58.29K。
And the reason why we can do that is becau differences on the Celsius scale and the kelvin scale are the same thing.
之所以会出现这种情况是因为1℃和1K是一样大的。
The kelvin scale is just a shifted version of the Celsius scale.
热力学温度不过是将摄氏度平移了而已。
If you added 273 to each of the numbers, you would have the kelvin temperature, but then if you take the difference, it’s going to be the exact same difference.
如果这两个数同时加上273就可以得到热力学温度,但如果两者求差,结果会是一模一样。考研复试自我介绍
Either way you do it, 78.29 minus 20. So that’s how much we have to rai the temperature.
就跟直接78.29-20一样。好啦，这就是需要升高的温度。
So let’s figure out how much energy is required to rai that temperature.
然后我们来求升高温度需要多少能量。
So we want a delta T. We want to rai the temperature 58.29.
我们要升高ΔT。我们要将温度身高58.29。
vsasI'll stay in Celsius. Actually let me just change it to kelvin, becau that looks like what our units are given in terms of specific heat.
makelove什么意思
就用摄氏度吧。还是改成开尔文好了，这样看起来单位才跟热量挂钩。
So let me write that down. 58.29 kelvin is our change in temperature.
我写下来吧。58.29K是升高的温度
I could have converted either of the to kelvin first, then found the difference, and gotten
the exact same number.
我也可以先将它们换算成热力学温度再求差，结果是一样的。
Becau the Celsius scale and the kelvin scale, the increments are the same amount.
因为无论是摄氏度还是开尔文增量都相等
Now, that's our change in temperature.
好啦，这是温度的增量
Now how much ethanol are we trying to boil?
接着 要沸腾的乙醇有多少？
Well, it tells us right over here. It tells us that we're dealing with 1 kilogram of ethanol.
你看，这里有。它说一共有1kg的乙醇
And everything el they give us is in grams.
attitudes然后别的质量单位都是克
So let me just write that 1 kilogram, that's the same thing as 1,000 grams.
所以先来换算1kg，它等于1000gbride of the wind
We could just write it here.
我们写在这儿
1.00 kilogram is equal to--or let me write it this way--times 1,000 grams per 1 kilogram.
1.00kg就等于…这样好了乘以1000g/1kg。
芒果的英文
The cancel out. This is the same thing as 1,000 grams.
这里消掉了这就等于1000g了。
Although the reality is we only have three significant digits, this makes it look like we have four.
虽然本来只有3位有效数字，这里变成了4位
So we have 1,000 grams times 1,000 grams.
所以一共是有1000g这里乘以1000g
And then we just multiply this times the specific heat of ethanol.
然后再把这个乘上乙醇的比热容
The specific heat capacity of ethanol right here,2.44 joules per gram kelvin. So times 2.44 joules.
乙醇的比热容在这儿是2.44J/(g·K) 所以再乘2.44J…
Let me write it this way, 2.44 joules per gram kelvin. You e that the units work out.
这样写好2.44J/(g·K) ，这样单位就对了。
This kelvin is going to cancel out with that kelvin in the denominator.
这个“K”就和这个“K”抵消了
This gram in the numerator will cancel out with that gram.
这个“g”和那个“g”也抵消了。
demi
And it makes n. Specific heat is the amount of energy per mass per degree that is required to push it that 1 degree.
