SC8 Q2W4D2: Elements in Earth’s Subsystems

🎯 Learning Goals

At the end of the lesson, the learners will be able to:

1. Identify at least 5 naturally occurring elements in different Earth subsystems - atmosphere, hydrosphere, lithosphere, biosphere - with 80% accuracy.
2. Differentiate metals from nonmetals using at least 3 observable properties - conductivity, luster, malleability - in a classification activity.
3. Explain through a short written response how the occurrence of elements in Earth’s subsystems supports life and human activities.

🧩 Key Ideas & Terms

• Element - pure substance made of one type of atom.
• Metal - element that is usually solid, shiny, malleable, ductile, and a good conductor of heat and electricity.
• Nonmetal - element that is brittle, dull, and a poor conductor of heat and electricity.
• Earth’s Subsystems - four major systems where elements occur naturally: Atmosphere, Hydrosphere, Lithosphere, Biosphere.

🔄 Prior Knowledge

Activity: Earth’s Subsystems Match-Up

Show a diagram of the four Earth subsystems - atmosphere, hydrosphere, lithosphere, biosphere. Ask learners to name one element that belongs to each subsystem.

Guide Questions:

1. Which elements are present in the air we breathe.
2. Which elements are abundant in the ocean.
3. Which elements make up the rocks and soil.
4. Which elements are most common in the human body.

Show Answer

1. Atmosphere - Oxygen O₂, Nitrogen N₂, Argon Ar
2. Hydrosphere - Hydrogen H, Oxygen O, Sodium Na, Chlorine Cl, Magnesium Mg, Calcium Ca
3. Lithosphere - Iron Fe, Silicon Si, Aluminum Al, Calcium Ca, Potassium K, Sodium Na, Magnesium Mg
4. Biosphere - Carbon C, Hydrogen H, Oxygen O, Nitrogen N, Phosphorus P, Sulfur S

📖 Explore the Lesson - Discovery and Occurrence of Elements in Earth’s Subsystems

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1. Setting the scene - why study where elements occur.

Elements do not distribute randomly. Their occurrence is guided by physical states, chemical reactivity, and Earth processes like volcanism, weathering, ocean circulation, and biological cycling. Studying where elements occur helps learners explain everyday phenomena - why oceans are salty, why irons rust on land but not in the sky, why plants need nitrogen and phosphorus, and why silicon is linked to computer chips. This knowledge also supports human decisions - where to mine, how to manage water, and which fertilizers to use for crops.

Guiding question: How does the natural distribution of elements influence human settlements and industries.

Show Answer

Civilizations often develop near rivers and coastlines because water supplies dissolved nutrients and supports transport. Lithosphere deposits of iron, copper, and aluminum attract mining and manufacturing. Atmosphere and biosphere provide breathable air and fertile soils. These patterns drive agriculture, trade, and technology hubs.

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2. Atmosphere - elements in the air

The atmosphere is a mixture of gases dominated by nitrogen and oxygen with minor components like argon and carbon dioxide. Elements occur as molecules or noble gases. Nitrogen occurs as N₂ - a stable, non reactive diatomic molecule. Oxygen occurs as O₂ - critical for respiration and combustion. Argon is a noble gas - chemically inert. Carbon occurs in carbon dioxide CO₂ - small in percentage but essential for photosynthesis.

• Nitrogen N₂ ~ 78 percent - stable gas, not directly usable by most plants. Microorganisms and lightning convert N₂ into usable forms like nitrate and ammonium.
• Oxygen O₂ ~ 21 percent - supports aerobic respiration and combustion processes.
• Argon Ar ~ 1 percent - inert, used in lighting and welding shields.
• Carbon dioxide CO₂ - variable trace gas, essential for photosynthesis and climate regulation.

Checkpoint: Predict what happens to fire behavior on a mountain compared with sea level.

Show Answer

At higher altitude the partial pressure of oxygen is lower, so combustion is less efficient. Flames may be weaker and fuels can be harder to ignite.

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3. Hydrosphere - elements in water

The hydrosphere contains water as H₂O and many dissolved ions. Sodium and chlorine ions account for most of seawater salinity as Na⁺ and Cl⁻. Magnesium, calcium, and potassium are significant too. Rivers carry dissolved elements from weathered rocks to the ocean. Marine organisms depend on these elements to build shells and skeletons, regulate osmosis, and conduct nerve impulses.

• Hydrogen and oxygen - compose water molecules that dominate the hydrosphere.
• Sodium and chlorine - present as ions, forming common salt that controls ocean chemistry.
• Magnesium and calcium - critical for marine life, shell formation, and water hardness.
• Potassium - an important electrolyte for biological function.

Investigation idea: Compare labels on bottled mineral waters and list the top three ions by concentration.

Show Answer

Typical results show calcium Ca²⁺, magnesium Mg²⁺, bicarbonate HCO₃⁻ and sometimes sodium Na⁺ and sulfate SO₄²⁻. Exact values vary by source.

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4. Lithosphere - elements in rocks and minerals

The lithosphere stores most of Earth’s solid elements in minerals. Oxygen and silicon dominate as silicate minerals such as quartz and feldspar. Aluminum and iron are abundant metals. Calcium, sodium, potassium, and magnesium round out the common elements in the crust. Weathering breaks rocks apart, releasing ions to soils and waters. Human societies extract ores like bauxite for aluminum, hematite and magnetite for iron, and chalcopyrite for copper.

Element	Common host mineral or ore	Typical use
Silicon Si	Quartz SiO₂, sand	Glass, electronics
Aluminum Al	Bauxite Al ores	Aircraft, cans
Iron Fe	Hematite Fe₂O₃, Magnetite Fe₃O₄	Steel production
Calcium Ca	Calcite CaCO₃	Cement, bones
Sodium Na	Feldspars	Glass, chemicals

Checkpoint: Why are silicates the most common minerals in the crust.

Show Answer

Because oxygen and silicon are the two most abundant elements in the crust and they form stable frameworks under crustal conditions.

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5. Biosphere - elements in living things

Life uses a narrow set of elements in large amounts known as CHNOPS - carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. Carbon forms chains and rings that become proteins, carbohydrates, fats, and nucleic acids. Hydrogen and oxygen dominate water and organic compounds. Nitrogen is central in amino acids and nucleic acids. Phosphorus appears in DNA and energy carriers like ATP. Sulfur stabilizes protein shapes. Trace elements like iron, iodine, and magnesium are vital for hemoglobin function, thyroid hormones, and enzyme activity.

Guided prompt: Explain how oxygen participates in both the biosphere and the atmosphere.

Show Answer

Oxygen gas O₂ in the atmosphere is inhaled by organisms for cellular respiration in the biosphere, producing energy and releasing carbon dioxide that returns to the atmosphere.

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6. Metals and nonmetals - property patterns

Metals and nonmetals show contrasting physical properties that influence where they are found and how humans use them. Metals usually appear in the lithosphere as ores and native metals. Nonmetals often occur as gases in the atmosphere or as molecular solids. Recognizing these properties helps learners infer likely subsystem occurrence and applications.

Property	Metals	Nonmetals
Conductivity	Good conductors	Poor conductors
Appearance	Shiny, lustrous	Dull
Shape	Malleable, ductile	Brittle
State at room temperature	Mostly solids except mercury	Solid, liquid, or gas
Density and melting point	Often high	Often lower

Quick check: Classify iron, oxygen, gold, sulfur as metal or nonmetal.

Show Answer

Iron - metal, Oxygen - nonmetal, Gold - metal, Sulfur - nonmetal.

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7. Worked classification by subsystem

Classify elements by where they most commonly occur in nature. Some span multiple subsystems, but one may dominate.

• Hydrogen - hydrosphere as part of H₂O.
• Carbon - biosphere in biomolecules.
• Oxygen - atmosphere and biosphere for respiration.
• Iron - lithosphere in ores and soil minerals.
• Helium - atmosphere in trace amounts.

Now you try: Place nitrogen, sodium, calcium, and phosphorus into subsystems based on occurrence and function.

Show Answer

Nitrogen - atmosphere, Sodium - hydrosphere as seawater ion, Calcium - lithosphere in minerals and also biosphere in bones, Phosphorus - biosphere in DNA and ATP and lithosphere in phosphate rocks.

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8. Human applications and sustainability links

Understanding element occurrence links science to daily life and the Sustainable Development Goals. Agriculture relies on nitrogen, phosphorus, and potassium fertilizers to sustain yields. Health depends on trace elements like iron and iodine. Technology uses silicon and rare earth elements for electronics and magnets. Environmental stewardship requires balancing cycles of carbon and nitrogen to avoid climate and water quality problems.

• Agriculture - nitrogen, phosphorus, and potassium support plant growth and yield.
• Health - iron deficiency causes anemia, iodine deficiency affects thyroid function.
• Technology - silicon chips, lithium batteries, and copper wiring depend on lithosphere resources.
• Environment - carbon and oxygen cycles regulate climate and respiration.

Critical thinking: Explain why communities invest in soil testing and water quality monitoring.

Show Answer

Soil testing reveals nutrient elements available for crops and guides fertilizer use. Water monitoring tracks dissolved elements and contaminants to protect health and ecosystems.

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9. Synthesis - build a 4 circle concept map

Draw four labeled circles - atmosphere, hydrosphere, lithosphere, biosphere. Place at least three elements in each circle. Add one sentence explaining how each subsystem supports human life. This map will serve as a study guide and a bridge to the assessment on Day 4.

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10. References

• Helmenstine, A. M. 2020. What are the elements in the human body. ThoughtCo.
• Zumdahl, S. S., Zumdahl, S. A., and DeCoste, D. 2018. Chemistry, 10th Ed. Cengage Learning.
• Silberberg, M. 2013. Chemistry - The Molecular Nature of Matter and Change. McGraw Hill Education.
• Madriaga, E. 2015. Science Links - Worktext for Scientific and Technological Literacy. Rex Book Store Inc.

💡 Example in Action - 5 worked examples with 5 mini tasks

Example 1 - Oxygen in the atmosphere

Description - Oxygen O₂ makes up about 21 percent of air and is essential for respiration. Occurrence - atmosphere and biosphere.

Now you try 1: Where is nitrogen N₂ most abundant and why is it important.

Show Answer

Nitrogen is most abundant in the atmosphere about 78 percent. It is important because nitrogen fixation supplies forms usable by plants for proteins and DNA.

Example 2 - Sodium in the hydrosphere

Description - Sodium Na ions combine with chlorine Cl to form NaCl that dominates ocean salinity. Occurrence - hydrosphere.

Now you try 2: Which element together with sodium gives seawater its salty taste.

Show Answer

Chlorine Cl as chloride ions.

Example 3 - Iron in the lithosphere

Description - Iron Fe is common in crustal rocks and is mined to make steel. Occurrence - lithosphere.

Now you try 3: Which element in quartz is the second most abundant in the crust after oxygen.

Show Answer

Silicon Si.

Example 4 - Carbon in the biosphere

Description - Carbon C forms the backbone of organic molecules like proteins and nucleic acids. Occurrence - biosphere.

Now you try 4: Which element along with carbon is essential for proteins and growth.

Show Answer

Nitrogen N.

Example 5 - Helium in the atmosphere

Description - Helium He is a noble gas present in trace amounts in the atmosphere and used in balloons and cooling systems.

Now you try 5: Which noble gas in the atmosphere is used for lighting signs.

Show Answer

Neon Ne.

📝 Try It Out - 10 items

Directions: Answer the following questions and classify or identify occurrence by subsystem.

1. Which subsystem is oxygen O₂ most abundant in.
2. In which subsystem is iron Fe mostly found.
3. The saltiness of seawater is due to which two elements.
4. Which subsystem contains the CHNOPS elements essential for life.
5. Which element makes up about 78 percent of Earth’s atmosphere.
6. Where is silicon Si commonly found.
7. Which subsystem does hydrogen H belong to if we consider its role in water.
8. Which element is widely used in electronics and is abundant in the lithosphere.
9. Which element is essential for respiration and forms about 21 percent of the atmosphere.
10. Which noble gas in the atmosphere is used for lighting signs.

Show Answer

1. Atmosphere
2. Lithosphere
3. Sodium Na and Chlorine Cl
4. Biosphere
5. Nitrogen N₂
6. Lithosphere sand and quartz
7. Hydrosphere
8. Silicon Si
9. Oxygen O₂
10. Neon Ne

✅ Check Yourself - 10 item mixed quiz

Directions: Answer the following questions.

Part A - Multiple choice 1 to 4

1. Which element is most abundant in Earth’s atmosphere. a. Oxygen O₂ b. Nitrogen N₂ c. Carbon dioxide CO₂ d. Argon Ar
2. Which subsystem contains most of Earth’s silicon Si. a. Atmosphere b. Hydrosphere c. Lithosphere d. Biosphere
3. Which group of elements CHNOPS are considered the building blocks of life. a. Copper Helium Neon Oxygen Phosphorus Sulfur b. Carbon Hydrogen Nitrogen Oxygen Phosphorus Sulfur c. Calcium Hydrogen Nickel Oxygen Potassium Sodium d. Cobalt Helium Nitrogen Oxygen Palladium Silver
4. Which subsystem contains dissolved sodium Na and chlorine Cl. a. Atmosphere b. Hydrosphere c. Lithosphere d. Biosphere

Part B - True or false 5 to 7

5. Helium is a noble gas found in the lithosphere.
6. Iron Fe is mostly mined from the lithosphere.
7. Nitrogen is important for living organisms because it is used in proteins and DNA.

Part C - Short answer 8 to 10

8. Name two elements found in the biosphere and explain their importance.
9. Why is oxygen O₂ important in both the atmosphere and biosphere.
10. Which subsystem would you study to learn about minerals like quartz and bauxite.

Show Answer Key

Part A
1. b - Nitrogen N₂
2. c - Lithosphere
3. b - Carbon Hydrogen Nitrogen Oxygen Phosphorus Sulfur
4. b - Hydrosphere

Part B
5. False - helium is in the atmosphere
6. True
7. True

Part C - sample answers
8. Carbon - backbone of organic compounds. Nitrogen - part of proteins and DNA.
9. Oxygen supports cellular respiration and combustion processes that sustain life and technology.
10. Lithosphere.

🚀 Go Further - Enrichment and remediation

Directions: Choose at least one activity to complete.

1. Element collage - subsystems map
   Create a poster with the four Earth subsystems and add three elements to each.
   Example

   Atmosphere - oxygen nitrogen carbon dioxide. Hydrosphere - hydrogen sodium chlorine. Lithosphere - silicon aluminum iron. Biosphere - carbon phosphorus sulfur.
2. Fertilizer research project
   Research nitrogen phosphorus and potassium for plant growth.
   Example

   Nitrogen - leaf growth proteins. Phosphorus - roots flowers DNA. Potassium - disease resistance strong stems.
3. Metal or nonmetal sort
   Make two columns labeled metals and nonmetals and list five elements with uses.
   Example

   Metals - Fe construction, Al airplanes, Cu wires, Au jewelry, Na lamps. Nonmetals - O respiration, N fertilizers, S proteins, P DNA, C fuels.
4. Life without it - oxygen
   Write a paragraph on what would happen if Earth had no oxygen.
   Sample idea

   Most life forms that rely on aerobic respiration would perish, combustion would be limited, and ecosystems would collapse.
5. Periodic table explorer
   Pick one element from each subsystem and record symbol, atomic number, and one use.
   Example

   Atmosphere - N 7 fertilizers. Hydrosphere - Na 11 salt. Lithosphere - Si 14 electronics. Biosphere - C 6 organic molecules.

🔗 My Reflection

Guiding questions

Answer in your notebook.

1. Which Earth subsystem did I find most interesting today and why.
2. Which element do I think is most important for human survival.
3. How do elements in the lithosphere and hydrosphere affect my daily life.
4. What new insight did I gain about the natural distribution of elements.

Reflection checklist

Put a check mark for items you agree with.

• I can name at least two elements in each Earth subsystem.
• I understand the difference between metals and nonmetals.
• I can explain why CHNOPS elements are essential for life.
• I can connect elements in the environment to human needs.
• I can explain why studying element occurrence is important in science.