Water Lesson 6: Heat-related properties of water - Practicing Science Together: A One-room Schoolhouse Model for Authentic Inclusive Secular Science Experiences

Scientist You Should Know

Lewis Howard Latimer (1848-1928) invented many, many important technologies. One of them was an air conditioner based on evaporative cooling. More on his biography below, in the “Verbal” portion of “Response/Analysis.”

There are two major heat-related (thermal) properties of water that make life possible: evaporative cooling and high heat capacity.

Introduction to evaporative cooling

There are a handful of reasons the Lewis Latimer air conditioner works. Here are a few of them. And here’s a great article:

https://www.mentalfloss.com/article/30993/why-does-60-degree-water-feel-colder-60-degree-air

If you watch this video on youtube, the caption has a TON of sources listed in case you want to know more.

The nice thing about Khan Academy is that, if you’re up for going down a rabbit trail, it will provide you the “next video” as they see it.

Introduction to heat capacity

5-ESS1-2. Represent data in graphical displays to reveal patterns of daily changes in length and direction of shadows, day and night, and the seasonal appearance of some stars in the night sky. [Clarification Statement: Examples of patterns could include the position and motion of Earth with respect to the sun and selected stars that are visible only in particular months.] [Assessment Boundary: Assessment does not include causes of seasons.]

For more analytical learners, there is a definition for “specific heat capacity,” and an equation that can be used to analyze data.

Check out the relationship between water’s heat capacity and climate.

The fact that water essentially carries heat around explains many of the weather patterns on Earth. This website gives the best explanation I’ve seen, but you know how I like primary sources. I can’t find any for this guy’s work. It does seem to be supported by everything else I read. Apparently a 2011-ish study disproved the idea of the Gulf Stream, but I’m having trouble finding that publication also. None of this is considered primary literature, but you can give it a look: https://www.scientificamerican.com/article/new-simulations-question-gulf-stream-role-tempering-europes-winters/ and https://www.livescience.com/13573-east-coast-colder-europe-west-coast.html

Side note on Thermal Pollution

This is an interesting perspective on human impacts. Organisms adapt to our activities, so in what ways do we need to take them into account when we change our patterns?

Experiencing the Science

Evaporative Cooling

Walk on hot concrete. Now pour some water on there and try it again. Walk on a wet spot that’s already there.

Three words: Spray fan mister

Heat Capacity

Let’s think about some ways to experience Specific Heat Capacity. The units of Specific Heat Capacity are J/(kg*K), which means energy per mass and heat. So, how much energy is required for every kg for every degree of temperature. It’s usually determined by the temperature change over the “amount of energy per mass,” like so:

I got this graph from wikipedia.

This whole “Heat added” thing is sort of hard to picture, but people often use time. One reason time is reasonable is because the kJ (kiloJoule) actually has time in it.

So, let’s do the amount of time heat has been added compared to the temperature.

A few warnings:

1. It’s dangerous to get oil up to the same temperature as boiling water, but it’s part of deep frying, so it’s a thing people do. Just be careful. OBSERVE FROM A DISTANCE OF AT LEAST 3 FEET FROM THE STOVE!

2. What about melted sugar? Heavens! Be careful! OBSERVE FROM A DISTANCE OF AT LEAST 3 FEET FROM THE STOVE!

3. What about other liquids like those we used in the Capillary Action experiment? Alcohols and acetone evaporate pretty fast. You need pressure to get them up to water’s boiling point, so it’s not safe. I suggest an immersion heater set low. Like the temperatures you would use for a fish tank.

What’s an immersion heater? There’s one in Sous vide cookers, but also in fish tanks. It’s a heater that goes into the liquid.

Alternatively, put some bowls of stuff outside in the sun and go out there and take some temperature measurements. (There are concerns in terms of control. Consider insulating the sides of your container and see if it matters. Probably it won’t matter much, because air itself is an insulator, but definitely try it!)

Response/Analysis

Mulitsensory

Use that spray fan mister, y’all.

Also, what is the deal with sous vide cooking? That’s some water magic. If you have one of those guys, you can set it to a nice warm bath water temperature. Be careful not to scald anyone!

Also, up above where I’m talking about deep frying and heating up sugar: that’s cooking. Eat some stuff! The thing about the sugar is that you can also heat it to different temperatures and get different candies. Obviously it’s gotta be grown-ups doing this sort of cooking because splashing that stuff on a person results in a nasty burn! OBSERVE FROM A DISTANCE OF AT LEAST 3 FEET FROM THE STOVE! But, once it’s cool, all of us can eat.

At the 33 minute mark of this documentary, an interesting sound experiment happens:

Minute 33:13 is roughly where you find the water temperature portion. More on why in the next lesson.

Creative

Choreograph a dance that demonstrates how water holds on to heat! Remember that hotter molecules move around more. Look at this table of specific heat capacities:

Can you do costumes to show what material you are, turn up the heat, and then turn the heat back down? What does each material do when it experiences heat?

Verbal

Check out this tour of Lewis Latimer’s house in Flushing, NY:

Analytical

Use the lab report format that is most appropriate for you.

I have some ideas, but you might have some too:

Try thawing something from the freezer under different conditions. How does your family thaw chicken? How do other people thaw chicken? My husband puts it on an upside-down metal pie tin and it thaws faster. What? Why?
Think about how you will measure how thawed the freezer item is. It’s a good idea to have a number. Maybe it’s how far you can poke a skewer into the item? What else can you think of?
How often do you need to make measurements? How many measurements would you like to have? What happens if everything is all thawed out by the time you measure it?

REMEMBER THAT RAW MEAT HAS GERMS. YOU CAN WEAR GLOVES, KEEP IT WRAPPED IN PLASTIC, OR MAKE SURE YOU WASH YOUR HANDS WHEN TOUCHING IT. CLEAN UP THE COUNTER WITH DISINFECTANT WHEN YOU’RE FINISHED.

Here’s something else you might find interesting (if not confusing): Why isn’t the Gulf Stream idea (that scientists held onto for years) so straightforward? It has to do with the fact that ocean currents AND air currents determine climate. Tricky. This article is blowing my mind. Some of the computer models are similar to the ones used to show that the Gulf Stream isn’t the only thing making the European Atlantic coast warmer than the North American Atlantic coast.