---
title: "Two metal blocks, \\(\\text{Block X}\\) and \\(\\text{Block Y}\\), are brought into contact inside an insulated container. The initial particulate state of the two blocks is shown in the diagram, where the length of each arrow represents the relative speed of a particle. Which of the following best describes the system after thermal equilibrium is reached?"
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url: "https://nerd-notes.com/ubq/119277/"
date_modified: "2026-08-19T12:39:37+00:00"
---

# Two metal blocks, \(\text{Block X}\) and \(\text{Block Y}\), are brought into contact inside an insulated container. The initial particulate state of the two blocks is shown in the diagram, where the length of each arrow represents the relative speed of a particle. Which of the following best describes the system after thermal equilibrium is reached?

Two metal blocks, \(\text{Block X}\) and \(\text{Block Y}\), are brought into contact inside an insulated container. The initial particulate state of the two blocks is shown in the diagram, where the length of each arrow represents the relative speed of a particle. Which of the following best describes the system after thermal equilibrium is reached?

![A legend maps: open circle = particle in Block X, filled circle = particle in Block Y, arrow = velocity vector of particle. The diagram shows two rectangular solid blocks touching at a central vertical boundary inside an insulated container. The left block (Block X) contains 6 open circles arranged in a 2 by 3 grid; each open circle has a long arrow attached representing high molecular speed. The right block (Block Y) contains 6 filled circles arranged in a 2 by 3 grid; each filled circle has a short arrow attached representing low molecular speed. No other particles, labels, text, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787143176-7Jiyjp.jpg)

- **A.** Energy has transferred as heat from \(\text{Block X}\) to \(\text{Block Y}\), and the average kinetic energy of the particles in \(\text{Block X}\) is equal to the average kinetic energy of the particles in \(\text{Block Y}\).
- **B.** Energy has transferred as heat from \(\text{Block Y}\) to \(\text{Block X}\), and the average kinetic energy of the particles in \(\text{Block X}\) remains greater than that of \(\text{Block Y}\).
- **C.** Energy has transferred as heat from \(\text{Block X}\) to \(\text{Block Y}\), and all molecular motion in both blocks has ceased.
- **D.** Energy has transferred as heat from \(\text{Block X}\) to \(\text{Block Y}\) until all particles in \(\text{Block X}\) have lower kinetic energy than all particles in \(\text{Block Y}\).

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119277/*