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Simple Science Experiments: Heat Exchange

Simple Science Experiments: Heat Exchange

W9ynNDOJBexDVpqyCMbaj0GUr4iPY05GZPhmCnxr4gw,XfAAQpNsoJ0NBHXNBghGMCmenw1j6FzfPG5o29FPmY8Ice cubes. Solid water. You know they form at really low temperatures, but how long does it take for it to melt?

This month we’ll be exploring the different ways objects heat up and cool down. We’ll be checking out how quickly ice melts in/on different materials, and we’ll even learn a little about what it means to be cold.

Materials:

Ice, a timer (a clock will do), hand sanitizer, pans, books, cups, and other materials for experimenting

Experiment 1: The Ice Melter

Will an ice cube melt faster in a glass of room temperature water or an empty glass? Take a guess and try to think why! (Explanations will follow all experiments.)cDimHNrHquY0NEGVjgkdPSvA4VVhU7Q2UuE-kKl9SBI,2ZFlxh4JktCNn0yqSX27DC-bzzsV-mmUhNJXhzATOTk

  1. Fill a glass with water and let it sit for about 20 minutes so it will be the same temperature as the air
  2. Put one ice cube in each container
  3. Start your timer to see which one melts first

Now that you have completed this portion of the experimenting, think about other substances that might make ice melt at different rates. Some ideas include a metal pan, a ceramic plate, a plastic cup, or a wooden surface. Can you think of more? To try this out: place pieces of ice on all the different surfaces and see which melts the ice fastest.

Experiment 2: Heat versus temperature

Did you know that when an object is “cold” you don’t actually feel it being cold? The object is just trying to warm up and transfers (or steals!) your heat to do this. An ice cube needs heat to melt, so when you touch it, it takes your heat! Weird! The questions for this experiment: If you put a metal pan and a book in the fridge for an hour, which one will be colder?

  1. Put a metal pan and a book in your refrigerator. They should be about the same size
  2. Take them out and feel which one is colder

After this is done, based on what you have learned put different things in the fridge to see how the materials affect how you feel them.

Experiment 3: What is the purpose of sweating?

Ever run around a lot and feel the sweat build up on your body? What is that all about? Here is a quick demonstration to show why.

  1. Take a bottle of room temperature hand sanitizer and squirt a blop right in the palm of your hand
  2. Don’t rub it in, instead, blow on it and let it sit there
  3. Wait until it evaporates

Cool, huh? (Pun intended.)

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Explanations:

There are a lot of explanations today, so get your brain ready.

Experiment 1: Ice melts a lot faster in the water than in the air. Different substances have the ability to transfer heat better than other, as well as have the ability to hold heat. The air can’t hold heat as well as water can, obviously. Different materials have different properties. Did you see the ice melt really fast on the metal plate? Metal is what is known as a conductor, while plastic is an insulator. That means in the metal heat can move really quickly through it, so the ice melts faster!

Experiment 2: The metal pan feels a lot colder than the book. They are the same temperature, though! Temperature is the measure of how fast the pieces the object is made of it moving. A solid moving? Yup. It is made of atoms that vibrate back and forth. The faster it vibrates, the more energy it has. But when you take them out, the properties of the metal are such that heat transfers much quicker than in the book. A conductor, again!

Experiment 3: Sweating is your body’s way of cooling down. The hand sanitizer acted like the sweat in this case. Even though it is room temperature and isn’t “cold” it sure feels it when it rests on your hand. That is because it is evaporating, and that process takes energy to do. All that sanitizer evaporates and takes the heat from your hand to do it, thus you get colder!

Experiment further:

This branch of science is thermochemistry, which deals with the heat changes of different substances/phases. You’ve only touched the tip of this science. Can you think of other things to test with heat exchange?

I hope you enjoyed this simple experiment. If you have more questions about this, specifically around the science fair aspect of this experiment, contact the author.

 

Steve Davala is a high school chemistry and physics teacher who likes to write and work with Photoshop. He’s got two kids of his own and subjects them to these science activities as guinea pigs. Follow him on Twitter or email him at steve.davala@gmail.com.

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