{ "cells": [ { "cell_type": "markdown", "id": "034faa4b-e846-46fb-bc39-58dee90b0c76", "metadata": {}, "source": [ "# Assignment 6\n", "\n", "Due Wednesday November 15 2023 (at start of class, or submitted electronically **via Brightspace** before class)\n", "\n", "Point values are indicated for each question.\n", "\n", "Total points: 35\n", "\n", "_Typos corrected 11/9/2023_" ] }, { "cell_type": "markdown", "id": "0a2311c9-dfb1-48d9-8b8d-f89ab289a00c", "metadata": {}, "source": [ "## Question 1\n", "\n", "_4 points_\n", "\n", "_(Problem 7.1 of the text)_\n", "\n", "By consulting Fig. 7.2 and Fig. 1.7, estimate the altitude at which the boiling point of water drops to room temperature (20ºC)." ] }, { "cell_type": "markdown", "id": "7d59096a-771c-4d2c-9c4c-265135fb3c78", "metadata": {}, "source": [ "## Question 2\n", "\n", "_6 points_\n", "\n", "_(Problem 7.3 of the text)_\n", "\n", "A pot contains one kg of ice at 0ºC and is placed on a stove with a burner that provides 900 W of power to the pot. Ignoring the heat capacity of the pot itself as well as other heat losses, compute the following, using a specific heat capacity $c_{water} = 4186$ J kg$^{-1}$ K$^{-1}$ for water.\n", "\n", "a) _(2)_ The time required to melt the ice\n", "\n", "b) _(2)_ The time required to raise the water temperature to boiling\n", "\n", "c) _(2)_ The time required to boil the water away. _Hint: use a value of latent heat of vaporization valid at the boiling point._" ] }, { "cell_type": "markdown", "id": "59228d9c-ee9b-46ba-ae5a-1d53236eb3ba", "metadata": {}, "source": [ "## Question 3\n", "\n", "_8 points_\n", "\n", "_(Based on Problem 7.4 of the text)_\n", "\n", "A container of pure water is set outside on a cold night and supercools to a temperature $T_{celsius}$ (expressed in ºC) without freezing. Once it is disturbed, however, ice crystals form and rapidly spread throughout the container until all that remains is a fairly uniform ice-water slush with temperature of 0ºC.\n", "\n", "a) _(6)_ Show that the fraction of ice $f$ in the resulting mixture depends on the initial temperature $T_{celsius}$ through this formula:\n", "\n", "$$ f = \\frac{-T_{celsius} ~c_{water}}{L_f} $$\n", "\n", "where $T_{celsius}$ is in ºC and is therefore a **negative number**.\n", "\n", "_Hint: First work out the energy required to warm the water up to 0ºC. Then work out the energy released by freezing the unknown fraction $f$ of ice at 0ºC. Set these two energies equal (which they must be in an isolated system) to determine the fraction of ice $f$._\n", "\n", "b) _(2)_ It is impossible to supercool pure water to less than about -40ºC without it spontaneously freezing. Therefore, what is the maximum fraction of ice that can be achieved from supercooled water without additional cooling?" ] }, { "cell_type": "markdown", "id": "9ee413ec-3cdf-4eca-8656-073ce1e0a363", "metadata": {}, "source": [ "## Question 4\n", "\n", "_5 points_\n", "\n", "_(Problem 7.5 of the text)_\n", "\n", "A chemist working in a laboratory requires a version of equation (7.18) that is valid in the vicinity of the boiling point of water. Rederive the coefficients $A$ and $B$ using $T_0 = 373$ K, noting that $e_{s0}$ at this temperature is equal to one standard atmosphere, and $L=2.26 \\times 10^6$ J kg$^{-1}$." ] }, { "cell_type": "markdown", "id": "0b315c76-e9e6-4ab3-8f54-021b671051ad", "metadata": {}, "source": [ "## Question 5\n", "\n", "_6 points_\n", "\n", "_(Problem 7.6 of the text)_\n", "\n", "Use equation (7.18) to find the dewpoint temperature $T_d$ corresponding to a mixing ratio $w$ of 20 g kg$^{-1}$ at a pressure $p$ of 1000 hPa and a temperature of 35CºC.\n", "\n", "_Hint: recall that the dewpoint satisfies the equation $ e = e_s(T_d)$, and vapor pressure can be calculated from mixing ratio and air pressure._" ] }, { "cell_type": "markdown", "id": "1cd12cae-b5da-45af-89ed-45686419a1fd", "metadata": {}, "source": [ "## Question 6\n", "\n", "_6 points_\n", "\n", "_(Problem 7.7 of the text)_\n", "\n", "On a humid day in the central of southeastern United States, one sometimes hears the casual comment that \"it is 90 degrees (Fahrenheit) and 90% humidity.\" What dewpoint (in ºF) would this combination represent? " ] }, { "cell_type": "code", "execution_count": null, "id": "c688eaa0-9070-4ac2-b0e9-6a4a3b4de62b", "metadata": {}, "outputs": [], "source": [] } ], "metadata": { "kernelspec": { "display_name": "Python 3 (ipykernel)", "language": "python", "name": "python3" }, "language_info": { "codemirror_mode": { "name": "ipython", "version": 3 }, "file_extension": ".py", "mimetype": "text/x-python", "name": "python", "nbconvert_exporter": "python", "pygments_lexer": "ipython3", "version": "3.11.4" } }, "nbformat": 4, "nbformat_minor": 5 }