Energy bar charts
For each of the situations described below, use an energy bar chart to represent the ways that energy is stored in the system and flows into or out of the system.
11. A cup of hot chocolate cools as it sits on the table. (10 points)
12 A tray of water $\left(20^{\circ} \mathrm{C}\right)$ is placed in the freezer and turns into ice cubes $\left(-8^{\circ} \mathrm{C}\right)$. (10 points)
Energy Fion
Fina

Quantitative problems
Be sure to show work and label quantities. Stiow the time-lemp kraph. Useful constants
$334 \mathrm{~J} / \mathrm{g} \quad$ Heat of fusion (Hi) (melting of freezing
$2260 \mathrm{~J} / \mathrm{h}$ Heat of vaporization (Hy) (evaporating or condensing)
$2.10 \mathrm{~N} / \mathrm{g}^{\circ} \mathrm{C} \quad$ Heat eapacity (c) of solid water
4. $18 \mathrm{Jg}^{\circ} \mathrm{C}$
Heat capacity (c) of liquid water
13. How much enersy must be absorled by a $150 \mathrm{~g}$ sample of wce at that melts?'10 points)
14. A 50.0 g samiple of hiquiat water freeres. How much oncory is involvod in this change? $(10$ points)
15. An ice cube tray full of rice (235g) at $-79^{\circ} \mathrm{C}$ is allowed to warm un to $0^{\prime} \mathrm{C}$. but daes not melt. How much energy must be absorbed by the contents of the tray in order tor this to huppen? (10 points)

Question

Energy bar charts
For each of the situations described below, use an energy bar chart to represent the ways that energy is stored in the system and flows into or out of the system.
11. A cup of hot chocolate cools as it sits on the table. (10 points)
12 A tray of water $\left(20^{\circ} \mathrm{C}\right)$ is placed in the freezer and turns into ice cubes $\left(-8^{\circ} \mathrm{C}\right)$. (10 points)
Energy Fion
Fina

Quantitative problems
Be sure to show work and label quantities. Stiow the time-lemp kraph. Useful constants
$334 \mathrm{~J} / \mathrm{g} \quad$ Heat of fusion (Hi) (melting of freezing
$2260 \mathrm{~J} / \mathrm{h}$ Heat of vaporization (Hy) (evaporating or condensing)
$2.10 \mathrm{~N} / \mathrm{g}^{\circ} \mathrm{C} \quad$ Heat eapacity (c) of solid water
4. $18 \mathrm{Jg}^{\circ} \mathrm{C}$
Heat capacity (c) of liquid water
13. How much enersy must be absorled by a $150 \mathrm{~g}$ sample of wce at that melts?'10 points)
14. A 50.0 g samiple of hiquiat water freeres. How much oncory is involvod in this change? $(10$ points)
15. An ice cube tray full of rice (235g) at $-79^{\circ} \mathrm{C}$ is allowed to warm un to $0^{\prime} \mathrm{C}$. but daes not melt. How much energy must be absorbed by the contents of the tray in order tor this to huppen? (10 points)

Accepted Answer

∻Solution∻ ‖ 1 ⋮ **Identify the process**: The problem involves the phase change of water from liquid to solid (freezing) and the associated energy changes. ‖‖ 2 ⋮ **Determine the mass of the sample**: The mass of the liquid water sample is given as $50.0 \, \text{g}$. ‖‖ 3 ⋮ **Use the heat of fusion**: The heat of fusion for water is $334 \, \text{J/g}$. This is the amount of energy required to change 1 gram of water from liquid to solid at $0^\circ \text{C}$. ‖‖ 4 ⋮ **Calculate the energy involved**: Multiply the mass of the water by the heat of fusion to find the total energy involved in the phase change. The formula is: $$ Q = m \cdot \Delta H_f $$ where $ Q $ is the energy, $ m $ is the mass, and $ \Delta H_f $ is the heat of fusion. $$ Q = 50.0 \, \text{g} \times 334 \, \text{J/g} = 16700 \, \text{J} $$ ‖ ∻Answer∻ ⚹ $16700 \, \text{J}$ ⚹ ∻Key Concept∻ ⚹ Heat of fusion ⚹ ∻Explanation∻ ⚹ The heat of fusion is the amount of energy required to change a substance from the solid phase to the liquid phase at its melting point. In this problem, it is used to calculate the energy involved in freezing liquid water. ⚹◊What is the heat energy required to melt a 150g sample of ice at a specific temperature?⍭ Generate me a similar question◊

Sia