07/15/2019: Science Notebook Ch. 14

Today’s soundtrack is Steel Panther: All You Can Eat, another over-the-top, ridiculously raunchy album from the incredibly talented hair metal parody group.

A quick update before I get started today:
At the beginning of the summer, I had put together a reading plan that would have let me finish reading Calculus Made Easy, Systematic Theology, and Everything You Need to Ace Science in One Big Fat Notebook before the summer’s end. Unfortunately, circumstances arose that have prevented me from maintaining the pace that I would have needed to keep if I was to successfully finish all three books. Rather than burning myself out in a futile effort to make happen what can’t happen, I’ve reevaluated my priorities and decided to focus on the Science Notebook so that I can finish it by the end of the summer in preparation for my upcoming course in the fall; I will still read the other two when I can, but I will not be able to finish them by summer’s end as planned.

So let’s get cracking! Today, I’m reading the fourteenth chapter of Everything You Need to Ace Science in One Big Fat Notebook, “Thermal Energy.”

The more we heat any substance, the faster its molecules move. Even when a substance is frozen solid, its molecules are still moving around, bumping into each other, resulting in constant kinetic energy. Scientifically, temperature is defined as “the average kinetic energy of molecules in a substance” (p. 137).

Most substances expand when heated, and contract when cooled. We use this principle to measure temperature: when the mercury in the glass tube heats, it expands, filling more of the glass tube. We commonly record temperatures in Celsius, Fahrenheit, or Kelvin.

We’ve already learned about potential and kinetic energies. Those same principles apply to a substance’s molecules: when we account for the sum of both “kinetic and potential energies in the molecules of a substance” (p. 139), we will be able to determine its thermal energy.

What we perceive as heat is actually thermal energy being passed to a cool substance from a warm substance. Interestingly, cool does not transfer; heat (thermal energy) transfers – in the same way that if I pour out a glass of water onto the ground, we don’t say that I’m filling the glass with air; we say that I’m emptying the glass of water. Let’s take the analogy a step further. Suppose I have a casserole dish half-full of water sitting on the counter, and a glass of water in my hand. If I place the glass of water on its side in the casserole dish, the water from the glass will merge with the water in the casserole dish. When the water comes to rest, the water in the reclining glass will be at the same height as the water in all the rest of the casserole dish. In the same way, thermal energy will transfer between two objects only until they are both the same temperature.

There are three ways that thermal transfer occurs:

  1. Conduction (transfer through direct contact)
  2. Radiation (transfer through electromagnetic rays)
  3. Convection (transfer through movement of a fluid or gas)

Summary:

  1. The difference between temperature and thermal energy is that the former is a measure of a substance’s average kinetic energy, and the latter is the sum of a substance’s potential and kinetic energies.
  2. If I have a large glass of juice and a small glass of juice that are the same temperatures, the larger one has more thermal energy, because it has more potential energy.
  3. Convection is the transfer of heat through the movement of a fluid such as water or air.
  4. Radiation is the kind of heat transfer that happens in a microwave.
  5. If I lick a Popsicle, the thermal energy travels from my tongue to the Popsicle through conduction.
  6. The formula to convert from Celsius to Kelvin is T(c) = T(k) – 273.5
  7. Thermal energy always moves from hot to cold substances high to low energy
    1. I was technically correct, but it wasn’t the answer they were looking for.
  8. When an object heats up, it expands. When an object cools down, it contracts.

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