Let's take a look at the following example question here. It says one of the hottest recorded days in the country was 128°F in Lake Havasu City, AZ. If the melting point of phosphorus is 44.15°C, would it exist as a solid or liquid on this extremely hot day?

All right, so we see that in the question we're dealing with units of Fahrenheit and Celsius. From the equations up above, we know what's the second one we're going to have to use in some way. So we have degrees Fahrenheit equals 1.8 times degrees Celsius plus 32. They're giving me the temperature in Lake Havasu in Fahrenheit, but I mean I need to compare it to this melting point of phosphorus which is in Celsius.

If the temperature I find is equal to or greater than 44.15°C, that means that phosphorus will melt and it will be in its liquid form. If the temperature on this extremely hot day is not at least 44.15°C, then it won't be hot enough and phosphorus will not melt and remain a solid. So I'm going to plug in what I have for Fahrenheit, which is 128 and this is 1.8°C + 32.

Subtract 32 from both sides. So when we do that we get 96 = 1.8 times degrees Celsius. Divide both sides now by 1.8 and now we'll have the temperature in Lake Havasu in degrees Celsius. So our degree Celsius here equals 53.3. Now we needed the temperature to be at least 44.15°C per phosphorus to melt. This answer is much greater than it, so yes, it's hot enough for phosphorus to melt, therefore it'll exist in its liquid form.

Now that we've seen this example on how to relate Fahrenheit to degree Celsius, move on to the next video and let's take a look at the practice question.