1. What is the enthalpy change when 0.025 kg of ice at 14°F is heated to become water at 120°F? Include a complete heating curve for this specific process. The specific heat of water is 4.184 J/g°C and for ice is 2.09 J/g°C. The heat fusion is 6.01 kJ/mol. Show all of your work, including units throughout the work. Report the final answer in the unit of kilojoule (kJ) and use the constants provided within this problem.
Your response must be at least 75 words in length.
2. Pick a substance (compound or mixture) and describe the intermolecular attractive interactions that exist between molecules or ions based on their composition and molecular structures. Also, explain why the substance does not have the other intermolecular forces. Your complete explanation should discuss all four intermolecular forces. Include a drawing of the Lewis structure with a detailed explanation of how that structure is obtained and relates to the four IMFs. Upload a picture of the drawing.
Your response must be at least 75 words in length.
3. On average, there are 62 different types of metal that go into the production of modern smartphones. Most of these metals are mined from third world countries, and some with very limited supplies. Identify one of these metals and discuss where that metal is sourced and the impacts to the planet regarding the mining of the metal.
How to Write Enthalpy Changes, Intermolecular Forces, and Critical Metals in Smartphones
Section 1: Enthalpy Change for Heating Ice to Water
Given
Mass of ice = 0.025 kg
Mass = 25 g
Initial temperature = 14°F
Final temperature = 120°F
Specific heat of ice = 2.09 J/g°C
Specific heat of water = 4.184 J/g°C
Heat of fusion = 6.01 kJ/mol
Molar mass of water = 18.015 g/mol
Step 1: Convert Temperatures to Celsius
Initial temperature Ti=(14−32)×59T_i=(14-32)timesfrac{5}{9}Ti=(14−32)×95 Ti=−10∘CT_i=-10^circ CTi=−10∘C
Final temperature Tf=(120−32)×59T_f=(120-32)timesfrac{5}{9}Tf=(120−32)×95 Tf=48.89∘CT_f=48.89^circ CTf=48.89∘C
Step 2: Heat the Ice from −10°C to 0°C
Formula q1=mcΔTq_1=mcDelta Tq1=mcΔT q1=(25 g)(2.09 J/g∘C)(10∘C)q_1=(25,g)(2.09,J/g^circ C)(10^circ C)q1=(25g)(2.09J/g∘C)(10∘C) q1=522.5 Jq_1=522.5,Jq1=522.5J q1=0.523 kJq_1=0.523,kJq1=0.523kJ
Step 3: Melt the Ice
Find moles. n=25g18.015g/moln=frac{25g}{18.015g/mol}n=18.015g/mol25g n=1.388 moln=1.388,moln=1.388mol
Heat required for melting. q2=nΔHfusq_2=nDelta H_{fus}q2=nΔHfus q2=(1.388)(6.01)q_2=(1.388)(6.01)q2=(1.388)(6.01) q2=8.34 kJq_2=8.34,kJq2=8.34kJ
Step 4: Heat Water from 0°C to 48.89°C
q3=mcΔTq_3=mcDelta Tq3=mcΔT q3=(25)(4.184)(48.89)q_3=(25)(4.184)(48.89)q3=(25)(4.184)(48.89) q3=5112 Jq_3=5112,Jq3=5112J q3=5.11 kJq_3=5.11,kJq3=5.11kJ
Step 5: Total Enthalpy Change
qtotal=q1+q2+q3q_{total}=q_1+q_2+q_3qtotal=q1+q2+q3 qtotal=0.523+8.34+5.11q_{total}=0.523+8.34+5.11qtotal=0.523+8.34+5.11 qtotal=13.97 kJboxed{q_{total}=13.97;kJ}qtotal=13.97kJ
Final Answer
The enthalpy change is approximately 13.97 kJ.
Heating Curve
Temperature
50°C /
/
/
/
0°C ---------------------- Water Heating
|
| Melting
|
-10°C _________/
Ice Heating
Heat Added →Section 2: Intermolecular Forces
Selected Substance
Water (H₂O)
Lewis Structure
..
H — O — H
..Oxygen has six valence electrons.
Each hydrogen contributes one electron.
Oxygen forms two single bonds with hydrogen.
Two lone pairs remain on oxygen.
The octet rule is satisfied because oxygen has eight electrons surrounding it.
Hydrogen atoms each have two electrons.
Intermolecular Forces Present
London Dispersion Forces
London dispersion forces occur in every substance because electrons constantly move and create temporary dipoles. Water contains these forces because all molecules possess electron clouds capable of instantaneous polarization.
Dipole–Dipole Forces
Water is a polar molecule because oxygen is significantly more electronegative than hydrogen. The bent molecular geometry causes an unequal distribution of charge, producing permanent dipoles that attract neighboring molecules.
Hydrogen Bonding
Water exhibits hydrogen bonding because hydrogen atoms are directly bonded to oxygen, which is highly electronegative. Hydrogen bonding is responsible for water’s unusually high boiling point, high specific heat, and strong surface tension.
Ion–Dipole Forces
Pure water does not exhibit ion–dipole interactions because there are no dissolved ions present. Ion–dipole attractions occur only when ionic compounds dissolve in water, such as sodium chloride.
Summary of the Four IMFs
| Intermolecular Force | Present? | Reason |
|---|---|---|
| London Dispersion | Yes | Present in every molecule |
| Dipole–Dipole | Yes | Water is polar |
| Hydrogen Bonding | Yes | Hydrogen bonded directly to oxygen |
| Ion–Dipole | No (pure water) | No ions are present |
Section 3: Metal Used in Smartphones
One important metal used in modern smartphones is cobalt. Cobalt is a critical component of rechargeable lithium-ion batteries because it improves battery stability, energy density, and lifespan. A significant portion of the world’s cobalt supply is mined in the Democratic Republic of the Congo, which produces more than two-thirds of global cobalt.
Although cobalt is essential for modern electronics, its extraction has created numerous environmental and social challenges. Mining operations often result in deforestation, soil degradation, water contamination, and habitat destruction. Heavy metals released during mining can pollute nearby rivers and groundwater, affecting ecosystems and human health. Additionally, artisanal mining operations have been associated with unsafe working conditions, child labor, and inadequate worker protections.
The growing global demand for smartphones, electric vehicles, and renewable energy storage has increased pressure on cobalt supplies. Manufacturers are investing in battery recycling technologies, developing batteries that require less cobalt, and exploring alternative battery chemistries to reduce dependence on newly mined cobalt. Sustainable mining practices, stronger environmental regulations, and responsible sourcing initiatives are also important strategies for reducing the environmental and social impacts associated with cobalt production.
References
Brown, T. L., LeMay, H. E., Bursten, B. E., Murphy, C., Woodward, P., & Stoltzfus, M. (2023). Chemistry: The central science (16th ed.). Pearson.
Petrucci, R. H., Herring, F. G., Madura, J. D., & Bissonnette, C. (2021). General chemistry: Principles and modern applications (12th ed.). Pearson.
U.S. Geological Survey. (2024). Mineral commodity summaries 2024. U.S. Department of the Interior.
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