DSE Geography — The Sustainable City Tutor Prep Guide | Density, waste and carrying capacity

2026-11-03

Tutor lesson-prep guides · Secondary Geography

Answers on the sustainable city are three slogans: plant trees, recycle, take the train. This lesson replaces them with numbers: 60,000 people on 40 hectares is 1500 per hectare; 3,000 households at 2.5 kg a day is 7.5 tonnes a day and 2738 tonnes a year; a bus carries 120 people while a car averages 1.5, a factor of 80.

Objectives — Students can: (1) compute density from population and site area and link it to urban form (60,000 people over 40 hectares gives 1500 per hectare); (2) scale household waste to a yearly total and to a post-recycling residue (7,500.0 kg a day, 2738 tonnes a year, 2250 kg a day saved at thirty per cent); (3) compare green space per person and vehicle occupancy to justify three concrete indicators (2.0 m2 per person, a factor of 80 between bus and car).

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Density	How is density calculated?	Population divided by area
Units	How many square metres are in a hectare?	10,000
Urban form	Which transport mode usually dominates a high-density city?	Public transport
Carrying capacity	What does carrying capacity mean?	The population or activity an environment can support without degrading

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0–8 min	Open with three numbers	One figure each for density, waste and occupancy	Copy them with units
8–20 min	Density and form	Same population on two different site areas	Compute both and state the consequences
20–32 min	Waste and capacity	Scale households to the city, then to a residue	Complete three lines of working
32–44 min	Transport and access	Compare bus and car for people carried and road space	Get the ratio and write one conclusion
44–52 min	Data question practice	One calculation, one comparison, one proposal	Eight minutes working alone
52–60 min	Exit check	Mark three answers on the spot	Work alone

03 Teaching script (read it out)

Scene 1: Density is division, but its consequences are not

40 hectares is 400,000 m2 for 60,000 people, so density is 1500 per hectare and 150,000 per square kilometre. Put the same population on 120 hectares and density falls to a third. Students must state consequences, not just numbers: high density makes walking and public transport viable, but squeezes green space and daylight per person and concentrates waste and sewage on one small patch of land.

Students should name two environmental pressures that rise with density.

Scene 2: Scale waste from households, then ask about reduction

3,000 households at 2.5 kg a day produce 7,500.0 kg, or 7.5 tonnes, a day and 2,738 tonnes a year. A thirty per cent recycling rate saves 2,250 kg a day, which is exactly thirty per cent. The common shortcut is to say recycling solves it, so make them compute: even at half, 3.8 tonnes still need processing every day, which is why reduction at source matters.

Students should state how many kilograms remain each day after thirty per cent recycling.

Scene 3: Transport sustainability is occupancy and road space

A bus carries 120 people and a car averages 1.5, so the bus moves 80 times as many people per vehicle, before counting parking. High density and public transport are two sides of one design: density sustains frequency, and frequency persuades people to leave the car. That causal chain is the skeleton of every explanation mark.

Students should explain why a high-density city can sustain rail service.

04 Question types and worked steps

Type	Example	Steps	Answer
Density calculation	60,000 people on 40 hectares: find density per hectare and per km2	1. Divide population by area 2. Convert hectares to km2 (x100) 3. State units	1500 per hectare, 150,000 per km2
Waste projection	3,000 households at 2.5 kg a day: annual total	1. Multiply by days 2. Convert kg to tonnes 3. Divide by 1000	7.5 tonnes a day, 2,738 tonnes a year
Per capita indicator	12 hectares of green space for 60,000 people	1. Convert hectares to m2 2. Divide by population 3. Compare with a planning standard	2.0 m2 per person
Proposal question	Write two sustainability proposals for the estate	1. Name the problem figure 2. Give the measure 3. State the expected reduction	Reduce waste at source; raise public transport share

Sanity check (teach this): Checks: 40 hectares is 400,000 m2, so 1500 per hectare is 150,000 per km2; an answer of 150 per km2 missed the factor of 100. A yearly total of 2,738 tonnes must be roughly 365 times the daily 7.5 tonnes, so a wrong order of magnitude goes back. Green space of 2.0 m2 per person is a size students can picture; 200 m2 means hectares were never converted.

05 Independent practice (3 questions)

Question	Answer	What to watch
People per hectare	1500	Did they divide by 40
People per km2	150,000	Did they multiply by 100
Annual waste	2,738 tonnes	Did they multiply by 365 and divide by 1000
Green space per person	2.0 m2	Did they convert hectares to m2

06 Common mistakes and what to say

Mistake	Student writes	Say this
Missing the unit conversion	Density is 1,500 people per km2	1,500 is per hectare; a km2 holds 100 hectares, so it is 150,000. A wrong unit invalidates the analysis that follows.
Recycling as the whole answer	Recycling alone solves the waste problem	Compute it: at thirty per cent, 5,250 kg still arrives every day. Source reduction has to be named or the numbers contradict the claim.
Proposals with no figures	Plant more trees and take the train	Every proposal needs a number behind it: how much green space, how many times the occupancy. Otherwise it is a slogan.
Density confused with liveability	High density is always unpleasant	Density is a number; liveability depends on green space per person, daylight, ventilation and services. The same density can feel completely different.

07 Homework (paper, section and question numbers)

Geography subject index — Revise the population chapter on density and natural change, then do the three questions here
Urban land use (S5 chapter) — Redo questions 1 and 2 on that page and link the land-use zones to density
Population ageing (S6 chapter) — Compare the transport and health needs of an ageing estate with a young one

08 Exit check (last 5 minutes)

Question	Answer	Decision
People per hectare	1500	Error: using 400 as the area
People per km2	150,000	Error: missing the factor of 100
Residue after thirty per cent recycling	5,250 kg a day	Error: writing reduce waste with no number
Bus against car occupancy	80 times	Error: dividing 120 by 120

09 Tutor FAQ

Do the numbers have to be memorised?

No individual estate figures, but three conversions must be instant: one hectare is 10,000 m2, one km2 is 100 hectares, one tonne is 1,000 kg. Marks come from units and reasoning.

Must every answer use the three pillars?

Environment, economy and society are the frame, but each pillar needs a number from this question. Listing the pillars without data answers nothing.

Does the Chinese paper differ?

Same structure: indicator, data, limitation, proposal. In Chinese, write the indicator in the first sentence of each paragraph just as you would write a topic sentence in English.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.