Understanding Thermal Equilibrium: The Basics of Liquid Interaction

Are the two liquids in thermal equilibrium if one is at 388 K and the other is at 288 K?

• A. Yes, they are at equilibrium
• B. No, they are not at equilibrium
• C. Only at equilibrium when mixed
• D. Depends on the mass of liquids

Answer: (B)

The two liquids are not in thermal equilibrium because thermal equilibrium occurs when two objects or systems reach the same temperature, and no net heat transfer takes place between them. In this case, one liquid is at 388 K, and the other is at 288 K. Since their temperatures are different, heat will flow from the hotter liquid (388 K) to the cooler liquid (288 K) until they reach the same temperature. Until that happens, they cannot be considered to be in thermal equilibrium. Temperature is the key factor determining thermal equilibrium. Therefore, regardless of other factors like the mass of the liquids or their specific heat capacities, if their temperatures are not equal, they are not in equilibrium. Even when mixed, as suggested by one of the choices, without reaching the same final temperature first, they cannot achieve thermal equilibrium.

When it comes to the world of physical science, understanding thermal equilibrium can feel a bit elusive. But let’s break it down—particularly as you gear up for your University of Central Florida (UCF) PSC1121 final exam. You might have come across the question about two liquids at different temperatures—388 K and 288 K, to be precise. So, are they in thermal equilibrium? Here’s the scoop: the answer is a resounding “no.”

You know why? Thermal equilibrium occurs only when two systems—or in this case, liquids—reach the same temperature. If they’re at different temperatures, like our example, heat flows from the hotter liquid (388 K) to the cooler one (288 K). Until those temperatures align, no equilibrium exists. This is like having two friends where one is excitedly telling you a story while you're still processing the last tale they shared—you both need to be at the same point of excitement, or in this case, temperature.

Let’s take a second to unpack why that’s so crucial. When two substances are at uneven temperatures, the laws of thermodynamics dictate that the heat moves toward equilibrium. Just imagine putting a hot stone in a cold stream; over time, the stone cools down while the stream gets a bit warmer until both balance out. It’s that straightforward, and yet, it can trip you up if you’re not careful when hitting the books for your exam.

Now, to clarify, the mass of the liquids or their specific heat capacities doesn’t change the fact that thermal equilibrium can only exist when temperatures are equal. Even if you mix those liquids, they’re still not at equilibrium if they don’t share a common temperature first. So, without that magical moment of temperature convergence, they’re in a continuous state of heat transfer—making it impossible for equilibrium to be established.

So here’s the thing: as you prep for your PSC1121 exam, keep these principles in your toolkit. They aren’t just abstract concepts; they’re crucial to the everyday processes happening around you. Whether you're heating soup or understanding how our climate systems interact, the core principles of thermal dynamics govern our physical world.

Just remember, if you find yourself pondering thermal equilibrium during your study sessions, think about heat transfer and temperature—but also try and relate it to real-life scenarios. That’s often the key to remembering those complex concepts and acing your test. After all, science isn’t just a study of dry theories; it’s about understanding the world around us, one exciting question at a time!