F. Gases and Atmospheric Chemistry · Gases and Atmospheric ChemistryHuman Activities, Technology and Air Quality: Your Carbon Footprint
F1.1 F2.4About 70 minutes
Learning goals- I can analyse how smelting, vehicles and home heating affect air quality.
- I can explain cumulative and trans-boundary effects of air pollution.
- I can explain what a catalytic converter does and does not do.
- I can calculate direct CO₂ emissions from fuel use.
- I can propose and evaluate specific ways to reduce my carbon footprint.
Words to know
cumulative effect
An effect that builds up because many emissions add together or accumulate over time.
carbon footprint
The total greenhouse gas emissions, as mass of CO₂ or CO₂-equivalent, caused by an individual's or group's activities.
smelting
Extracting a metal from its ore by heating and chemical reactions; sulfide ores release SO₂.
catalytic converter
A device in a vehicle's exhaust that uses catalysts to convert CO, NOx and hydrocarbons into CO₂, N₂ and H₂O.
catalyst
A substance that speeds up a reaction without being used up.
trans-boundary pollution
Pollution that crosses provincial or national borders, carried by wind or water.
Small sources, big effects
One car's exhaust seems trivial. One furnace, one barbecue, one wood stove: each is small. But Canada has tens of millions of vehicles and homes. Air pollution is cumulative: emissions from many sources add up, some pollutants (like CO₂) stay in the atmosphere for centuries, and winds carry pollutants hundreds of kilometres across provincial and national borders. This lesson uses the chemistry from the whole unit to analyse how technologies and everyday activities affect air quality, and what you can do about your own carbon footprint.
Case study 1: Smelting in Sudbury
The Sudbury area has some of the world's richest nickel and copper deposits. The metals occur as sulfide ores. Roasting and smelting them releases sulfur as SO₂, for example: 2 NiS + 3 O₂ → 2 NiO + 2 SO₂.
For much of the 1900s, smelters in the area released very large amounts of SO₂. Combined with logging and open-air roasting, this left large areas of blackened, nearly bare rock and acidified lakes. In 1972, Inco (now Vale) completed the Superstack, a 381 m chimney. It improved local air quality by dispersing the SO₂ high into the air, but it didn't reduce the total emitted: it spread the acid over a wider area, adding to acid deposition downwind. That is a classic example of a cumulative and trans-boundary effect.
Real improvement came from chemistry: smelters began capturing SO₂ and converting it into sulfuric acid to sell (2 SO₂ + O₂ → 2 SO₃; SO₃ + H₂O → H₂SO₄), and changing their processes. Emissions are now a small fraction of their peak, and the company has since replaced the Superstack with smaller, more modern stacks. Since 1978, the community's regreening program has spread crushed limestone on acidic soils (CaCO₃ neutralizes acid) and planted millions of trees. Many lakes and hillsides have recovered.
Case study 2: Gasoline vehicles
A gasoline engine burns hydrocarbons: 2 C₈H₁₈ + 25 O₂ → 16 CO₂ + 18 H₂O. Real engines aren't perfect, so the exhaust also contains CO (incomplete combustion), NOx (from N₂ and O₂ in the air at high temperature), unburned hydrocarbons (VOCs) and particles.
A catalytic converter in the exhaust system speeds up reactions that turn these into less harmful gases. A ceramic honeycomb coated with platinum, palladium and rhodium gives the gases a huge surface on which to react. But notice: the converter turns CO into CO₂. It reduces smog-forming pollutants, not greenhouse gases. The only ways to reduce CO₂ from a vehicle are to burn less fuel or use a different energy source.
Your carbon footprint
A carbon footprint is the total amount of greenhouse gases (expressed as mass of CO₂ or CO₂-equivalent) released because of a person's, family's or organization's activities. Stoichiometry lets you calculate the direct part:
- Gasoline: about 2.3 kg of CO₂ per litre burned (you calculated about 2.2 kg for pure octane in the Gas Stoichiometry lesson).
- Natural gas (mostly methane) for heating: CH₄ + 2 O₂ → CO₂ + 2 H₂O. One cubic metre of natural gas makes roughly 1.9 kg of CO₂ (see Example 1).
- Electricity: depends on how it's generated. In Ontario, most electricity comes from nuclear and hydro power, which release very little CO₂ while operating, so electricity here usually has a smaller footprint than in places that burn a lot of coal.
Indirect emissions (manufacturing the things we buy, growing food, flights) also count, but are harder to calculate.
Worked exampleExample 1: CO₂ from a cubic metre of natural gas
Treat natural gas as pure methane. Gas meters measure volume at about 15 °C and 101.3 kPa. What mass of CO₂ forms when 1.00 m³ of methane burns?
- Moles of CH₄: V = 1000 L, T = 288 K. n = PV ÷ RT = (101.3)(1000) ÷ [(8.314)(288)] = 42.3 mol
- CH₄ + 2 O₂ → CO₂ + 2 H₂O: mole ratio 1 : 1, so n(CO₂) = 42.3 mol
- Mass: 42.3 mol × 44.01 g/mol = 1.86 × 10³ g = 1.86 kg
About 1.9 kg of CO₂ per cubic metre of natural gas.
Worked exampleExample 2: A family's direct footprint
A family drives 1500 L of gasoline a year and heats with 2000 m³ of natural gas. (a) Estimate their direct CO₂ emissions. (b) They start carpooling and walking for short trips (20 % less driving) and lower the thermostat and add weather stripping (15 % less gas). How much CO₂ do they save?
- (a) Car: 1500 L × 2.3 kg/L = 3450 kg. Heating: 2000 m³ × 1.9 kg/m³ = 3800 kg. Total = 7250 kg ≈ 7.3 t.
- (b) Car: 1200 L × 2.3 = 2760 kg. Heating: 1700 m³ × 1.9 = 3230 kg. New total = 5990 kg.
- Saving = 7250 − 5990 = 1260 kg
(a) About 7.3 t of CO₂ per year. (b) A saving of about 1.3 t a year, roughly 17 %, from small changes.
The family's yearly CO₂ from driving and home heating, before and after the changes in Example 2.Proposing reductions: think like a chemist
A good proposal is specific, measurable and realistic, and it weighs trade-offs. For example:
- Replace short car trips with walking, cycling or transit: every litre of gasoline not burned avoids about 2.3 kg of CO₂, plus CO, NOx and VOCs.
- Avoid idling in drive-throughs and while waiting: an idling engine burns fuel and makes exhaust while going nowhere.
- Heat and cool efficiently: lower the thermostat in winter, seal drafts, consider a heat pump.
- Electric vehicles: no tailpipe emissions, and on Ontario's mostly low-carbon grid, much lower CO₂ per kilometre. Trade-off: making the battery uses energy and mined metals (some of them smelted, like the nickel from Sudbury).
Always ask: does the change reduce a pollutant, or just move it somewhere else (like the Superstack)?
Hands-on activityCarbon footprint audit
You need: a notebook, a calculator, and help from a grown-up to find household information (a recent natural gas bill, the car's fuel-consumption rating in L/100 km, and the odometer).
- Driving: for one week, record the kilometres driven by the family car. Fuel used (L) = km × (L/100 km) ÷ 100. CO₂ = L × 2.3 kg.
- Heating: find the natural gas used last month on the bill (in m³). CO₂ = m³ × 1.9 kg. Note the month: winter bills are much bigger.
- Scale up: estimate the yearly totals.
- Propose: choose three realistic changes your household could make. Estimate the CO₂ each would save, using the same factors.
- Evaluate: for each change, write one benefit besides CO₂ (for example, less NOx, saving money, exercise) and one difficulty.
What to look for: a car using 8.0 L/100 km for 300 km a week burns 24 L, making about 55 kg of CO₂ a week, or nearly 3 t a year. Changes that cut fuel burned have the biggest effect. Keep this audit: you'll compare it with Canadian initiatives in the next lesson.
Just for funSudbury is home to the Big Nickel, a 9 m tall model of a 1951 Canadian five-cent coin. It's a monument to the area's mining history. And yes: no matter how big it gets, it's still worth only five cents.
Your turn
1What does "cumulative effect" mean for air quality? Give an example.
Effects that build up because emissions from many sources add together or accumulate over time. Example: millions of vehicles together produce smog in a city, even though each car's exhaust is small.
2Write balanced equations for two reactions in a catalytic converter.
2 CO + O₂ → 2 CO₂; 2 NO + 2 CO → N₂ + 2 CO₂
3Why doesn't a catalytic converter reduce a car's CO₂ emissions?
It converts CO and hydrocarbons into CO₂, so it actually produces CO₂. CO₂ can only be reduced by burning less fuel.
4How much CO₂ comes from burning 45 L of gasoline (one tank)?
45 × 2.3 = 103.5 ≈ 100 kg
5Why did the Superstack improve air quality in Sudbury itself but not reduce acid deposition overall?
It released SO₂ much higher, so it was diluted before reaching the ground nearby, but the same total amount of SO₂ was emitted and was carried farther away, where it fell as acid deposition.
6Write the equation showing how the SO₂ captured at a smelter can become a useful product.
2 SO₂ + O₂ → 2 SO₃, then SO₃ + H₂O → H₂SO₄ (sulfuric acid, which can be sold).
More practice: warm-up
The total greenhouse gas emissions (as CO₂ or CO₂-equivalent) caused by a person's or group's activities.
2What gas is released when sulfide ores are smelted?
3Name the three metals used as catalysts in a catalytic converter.
Platinum, palladium and rhodium.
4About how much CO₂ comes from burning 1 L of gasoline?
5What does crushed limestone do to acidic soil?
It neutralizes the acid (CaCO₃ reacts with acid).
More practice: on your own
1A car uses 8.0 L/100 km and drives 15 000 km a year. Find its yearly CO₂ emissions. How much would be saved by a car using 5.0 L/100 km?
Fuel: 15 000 × 8.0 ÷ 100 = 1200 L → 1200 × 2.3 = 2760 kg. Efficient car: 750 L → 1725 kg. Saving ≈ 1035 kg (about 1.0 t) per year.
2Balance the roasting of nickel(II) sulfide: NiS + O₂ → NiO + SO₂
2 NiS + 3 O₂ → 2 NiO + 2 SO₂
3Write the balanced equation for limestone neutralizing sulfuric acid in soil.
CaCO₃(s) + H₂SO₄(aq) → CaSO₄(aq) + H₂O(l) + CO₂(g)
4A household switches its furnace from natural gas to an electric heat pump. Explain why this lowers CO₂ much more in Ontario than in a region that makes electricity mainly from coal.
In Ontario, most electricity comes from nuclear and hydro, which emit very little CO₂, so heating with electricity avoids the CO₂ from burning gas. Where electricity comes from coal, the power plant releases CO₂ instead, so the savings are much smaller (or none).
5Explain why reducing idling improves air quality in two ways.
It saves fuel, which reduces CO₂ (about 2.3 kg per litre not burned). It also reduces CO, NOx and VOCs released at street level, where people breathe them, for example near schools at pick-up time.
Challenge
1Coal is about 85 % carbon by mass. Estimate the mass of CO₂ released by burning 1.00 t of coal (assume all the carbon burns: C + O₂ → CO₂).
Carbon: 850 kg = 850 000 g; n = 850 000 ÷ 12.01 = 7.08 × 10⁴ mol. CO₂: 7.08 × 10⁴ × 44.01 = 3.11 × 10⁶ g ≈ 3.1 t. Burning 1 t of coal makes about 3 t of CO₂, because each carbon atom picks up two oxygen atoms from the air.
2Propose and evaluate one technology and one personal action that would reduce smog-forming emissions (not just CO₂) in a large city.
Technology: electric buses (no tailpipe NOx, VOCs or PM; quiet; but high purchase cost and need charging infrastructure). Personal action: cycling or transit instead of driving (cuts NOx, VOCs and CO at street level; may be limited by winter weather, distance or safety of bike routes). A good answer names the pollutants reduced and at least one trade-off.
3A barbecue uses 9.0 kg of propane in a summer. Calculate the CO₂ produced. C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O
n(C₃H₈) = 9000 ÷ 44.11 = 204 mol. n(CO₂) = 3 × 204 = 612 mol. m = 612 × 44.01 = 2.69 × 10⁴ g ≈ 27 kg of CO₂.
Quiz
1. Which statement about the Sudbury Superstack is most accurate?
2. A catalytic converter converts carbon monoxide into:
3. About how much CO₂ is produced by burning 20 L of gasoline?
4. Which change would reduce a household's direct CO₂ emissions the most, for most Ontario families?
5. SO₂ captured at a smelter can be turned into:
6. "Cumulative effects" on air quality means:
Big idea (F1.1): students analyse how technologies (smelting, gasoline vehicles, home heating) and everyday activities affect air quality, explain cumulative and trans-boundary effects, and propose specific, measurable ways to shrink their carbon footprint, using stoichiometry from the unit.
How to help: the carbon footprint audit works best with real numbers from your household. Share a gas bill and the car's fuel-consumption rating if you're comfortable; otherwise use the sample numbers. Discuss trade-offs honestly; there's no single perfect solution.
Common difficulties:
- Thinking catalytic converters reduce CO₂. They reduce CO, NOx and hydrocarbons.
- Treating dilution as a solution. Tall stacks move pollution; they don't remove it.
- Vague proposals ("pollute less"). Encourage numbers: litres saved, kilograms of CO₂ avoided.
Note: this lesson builds on the CO₂-from-gasoline calculation in the Gas Stoichiometry lesson.