Secondary 3 Science Tuition | Jalan Rajah Weekday or Weekend Parent Dilemma

Secondary 3 Science Tuition | Jalan Rajah · Weekday or Weekend Parent Guide

Secondary 3 Science tuition for Jalan Rajah parents should address whether a pupil can read a cumulative gas-volume graph and calculate the rate over a chosen interval. A number high on the vertical axis does not necessarily mean the reaction is currently fast. In our original fictional gas-collection model, the total eventually reaches 66 cm³ as the curve becomes flat. It is the change in volume over time that reveals an average rate.

The paper dataset records imaginary cumulative collector volumes of 0, 25, 44, 57, 64, 66 and 66 cm³ at elapsed times 0, 20, 40, 60, 80, 100 and 120 seconds. A separately labelled faster-treatment model reaches the same 66 cm³ plateau earlier. No actual chemical experiment was conducted, and the example does not provide instructions for producing or collecting any potentially hazardous gas.

NParks documents Jalan Rajah on the Whampoa Park Connector route from Toa Payoh Town Park toward Bendemeer Road. That place fact is unrelated to the fabricated Chemistry readings. The learning approach follows eduKate’s immutable Clementi three-student tutorial reference, with focused ninety-minute weekly small-group work near Sixth Avenue MRT. This article serves families searching near Jalan Rajah; it does not claim a chemical laboratory or centre there.

A weekday or weekend is useful only when the learner can think

Marked error	Alert weekday correction	Rested weekend task
Divides cumulative total by final time for every segment	Subtract both segment endpoints first	Work a full curved gas-volume graph
Calls graph height instantaneous reaction rate	Separate volume and gradient units	Discuss slopes, plateau and model limits
Believes a faster rate always means more product	Compare two equal-yield treatments	Analyse rate and total yield separately
Wants to mix chemicals at home	Use safe synthetic paper data	Study experiment design, not unsupervised reactions

Illustrative parent decisions, not available lesson bookings.

An alert weekday may efficiently repair a specific graph error while the test is fresh. A rested weekend might allow a complete table interpretation and unfamiliar transfer problem. Neither time guarantees higher marks; useful progress is visible when the child can choose the correct interval, calculate its rate and explain a plateau without prompts.

Original imaginary cumulative gas-volume dataset

Elapsed time	Original model gas collected	Faster model gas collected
0 s	0 cm³	0 cm³
20 s	25 cm³	40 cm³
40 s	44 cm³	59 cm³
60 s	57 cm³	66 cm³
80 s	64 cm³	66 cm³
100 s	66 cm³	66 cm³
120 s	66 cm³	66 cm³

Invented numerical graphs only; no gas source, reagent quantity or laboratory operation is supplied.

Chemistry chapters: reaction rates, curves and evidence

1. Reaction rate must be tied to a measured quantity
2. The chemical reaction should be understood before its graph
3. The vertical axis reports collected gas volume
4. The horizontal axis reports elapsed time
5. At zero seconds the collector begins at zero volume
6. After twenty seconds the model has 25 cubic centimetres
7. After forty seconds the model total is 44
8. At sixty seconds cumulative volume is 57
9. At eighty seconds the cumulative value is 64
10. At one hundred seconds it reaches 66
11. At 120 seconds it stays at 66
12. The rate trend is not a straight-line decrease
13. A cumulative graph’s slope indicates production rate
14. Instantaneous rate is not the same as interval-average rate
15. Rate is separate from total gas yield
16. Changing concentration can alter collisions
17. The faster-treatment model is a separate comparison
18. Initial-average rate is greater in the faster model
19. A faster plateau need not mean greater total yield
20. Temperature is a potentially important variable
21. Particle size and surface area can affect reaction rate
22. Catalysts provide another distinct causal mechanism
23. Pressure effects depend on reaction conditions
24. A plateau does not uniquely identify the limiting reactant
25. Converting cubic centimetres to cubic decimetres
26. Gas volume does not automatically give moles without conditions
27. A gas collector can have systematic limitations
28. A real safety procedure is not supplied here
29. The locality is not a source of gas-reaction measurements
30. An unfamiliar interval-rate exercise tests learning
31. A complete conclusion distinguishes process from evidence

1. Reaction rate must be tied to a measured quantity

Our original school dataset records cumulative gas volume in cubic centimetres as a hypothetical gas-evolving reaction proceeds. The values are an instructional model, not actual laboratory readings. A slope of that curve represents the rate at which the collector volume changes over time under the specified setup.

A student who calls every gas-volume number a reaction rate has omitted the time dimension. Volume and volume per unit time are different physical quantities; before calculating, the tutor should ask what the vertical and horizontal axes represent.

2. The chemical reaction should be understood before its graph

A familiar Chemistry context is the reaction of a suitable reactive metal with acid to generate a gas, but the numerical study is independent of any actual chemical mixing. For example, the conceptual magnesium–acid reaction can form hydrogen, which is flammable and not appropriate for unsupervised home demonstrations.

The article gives no practical recipe, amounts of chemicals or home collection procedure. The pupil can learn the interpretation from a paper model with the reacting substances treated abstractly. Laboratory work belongs under school approval and trained supervision.

3. The vertical axis reports collected gas volume

In the graph the vertical axis is cumulative collected gas volume in cm³, meaning the amount recorded by the idealised collector since the chosen start. It is not mass lost from a flask and is not the gas’s pressure or temperature.

A student who labels the axis ‘rate / cm³’ is mixing a rate word with a volume unit. Require the direct observation to be named before deriving interval rate values from differences between points.

4. The horizontal axis reports elapsed time

Time is measured in seconds from the stipulated start of the reaction. The values 0, 20, 40, 60, 80, 100 and 120 seconds are observation times, not separately measured reaction extents.

If a teenager divides each volume by the right-end time to describe a specific segment, the denominator may be incorrect because it neglects the segment’s starting time. Teach the difference between a clock reading and an elapsed interval.

5. At zero seconds the collector begins at zero volume

The imaginary table records 0 cm³ at time zero. This is a chosen baseline for cumulative gas captured in the model, not evidence that the laboratory air initially contained no gas or that every reaction must begin with a zero sensor reading.

A pupil should explain what the zero means in this measurement system. When interpreting another graph with an offset baseline, the appropriate method may require subtracting the initial reading rather than assuming it is always exactly zero.

6. After twenty seconds the model has 25 cubic centimetres

The cumulative collected gas volume at t=20 s is 25 cm³. The whole first twenty-second average collection rate is (25−0)/(20−0)=1.25 cm³/s.

That value does not prove the reaction was proceeding at 1.25 cm³/s at every instant. The model could have had a faster beginning and a slower ending within those twenty seconds, something the two endpoints alone cannot reveal.

7. After forty seconds the model total is 44

The hypothetical gas collection at 40 s totals 44 cm³ since the chosen start. It is not 44 additional cubic centimetres in the second twenty-second interval, because the collector already held 25 cm³ at 20 s.

To find the interval change subtract endpoint values: 44−25=19 cm³ during 20–40 s. The average over that interval is 19/20=0.95 cm³/s, less than in the original interval.

8. At sixty seconds cumulative volume is 57

The model table gives 57 cm³ at 60 s. From 40 to 60 seconds, the additional collected volume is 57−44=13 cm³, and the twenty-second interval average rate is 13/20=0.65 cm³/s.

A student who calculates 57/60=0.95 cm³/s has found the average from the beginning to 60 s rather than the specified local segment. Both are ratios, but they answer different questions.

9. At eighty seconds the cumulative value is 64

The hypothetical model collector reaches 64 cm³ at 80 s. The addition from 60 to 80 s is 64−57=7 cm³ over twenty seconds, so the corresponding interval average rate is 0.35 cm³/s.

The pupil should identify the slowing rate without attributing it automatically to a precise molecular explanation. The numbers support a decreasing interval production of collected gas; more evidence is needed to identify every factor.

10. At one hundred seconds it reaches 66

At 100 s the model cumulative volume reaches 66 cm³, only 2 cm³ greater than at 80 s. Over that final rising twenty-second interval, the average collection rate is 2/20=0.10 cm³/s.

The rate is not exactly zero during 80–100 s simply because the curve is becoming flat. A small positive change over that interval remains measurable in the stated paper data.

11. At 120 seconds it stays at 66

The fictional 120 s reading is also 66 cm³. The measured cumulative collector value is therefore unchanged between 100 and 120 s and the interval-average collected-volume rate there is zero.

This plateau is consistent with little further gas collected under the model, but a real experiment might plateau because of exhausted reactants, a leak, a blocked device or other conditions. The table alone does not prove the exact chemical mechanism.

12. The rate trend is not a straight-line decrease

Our six twenty-second interval averages are 1.25, 0.95, 0.65, 0.35, 0.10 and 0 cm³/s. They decline, but their successive differences are not all equal, so it would be inappropriate to assert a perfectly linear decay law from these values.

A tutor should ask students to compare multiple segments rather than assume a single graph slope applies across a curved dataset. The appropriate conclusion is that gas collection slows under the stated model.

13. A cumulative graph’s slope indicates production rate

The rise in cumulative volume is steepest in early intervals and becomes shallow as the model progresses. On equally scaled axes, a larger gradient corresponds to a higher rate of change of collected gas volume per time.

A line being higher on the graph does not mean the instantaneous reaction rate is greater there. At 100 s the cumulative volume is high while the following interval-average rate is zero. The height and slope represent different quantities.

14. Instantaneous rate is not the same as interval-average rate

An instantaneous rate refers to the local gradient at a particular time on a smooth underlying curve, while our difference quotient gives a finite-interval average. Extracting a precise instantaneous rate from sparse data would require an interpolation or fitted model and a stated method.

A child who labels 0.65 cm³/s ‘the exact rate at 50.000 seconds’ has gone beyond the observations. It can be described as the average for 40–60 s unless a justified tangent estimate is made.

15. Rate is separate from total gas yield

The model reaches a plateau of 66 cm³ in both a slower and a hypothetical faster treatment. The final yield and the time taken to approach it are different properties: one concerns total collected product, the other how quickly it appears.

A student should not assume a faster initial rate always means more total product. When the same limiting reactant amount is used under appropriate chemistry conditions, different kinetics can lead to similar final yields.

16. Changing concentration can alter collisions

Under collision theory, reactant concentration can affect encounter frequency in suitable systems, potentially changing the reaction rate. The exact magnitude and rate law are not determined merely by knowing one solution is more concentrated.

Our second synthetic treatment is explicitly designated ‘faster conditions’ rather than given a real acid concentration recipe. The goal is data interpretation, not a procedure for generating gas.

17. The faster-treatment model is a separate comparison

An independent hypothetical treatment uses cumulative gas volumes 0, 40, 59, 66 and 66 cm³ at 0, 20, 40, 60 and 80 seconds. It reaches its plateau by 60 seconds in the model, earlier than the first treatment’s 100-second plateau.

This does not imply that an observed increase in concentration is necessarily the only cause. We explicitly assume relevant reactant and apparatus conditions are otherwise matched for the classroom comparison.

18. Initial-average rate is greater in the faster model

In the second fictional treatment, the first twenty-second interval collects 40 cm³, giving 40/20=2.0 cm³/s average, compared with 1.25 cm³/s in the original model’s first interval.

The ratio 2.0/1.25=1.6 belongs only to those two initial-average rates. It does not prove the chemical rate constant increased by a factor of 1.6 or establish a reaction order.

19. A faster plateau need not mean greater total yield

Both invented treatments eventually record 66 cm³ of collected gas. Their shared plateau is a design choice illustrating that kinetics and total yield can differ. In a real reaction, final collected volume also depends on reactant amounts, gas escape, solubility, temperature, pressure and collection method.

A student who says the faster curve must end at twice 66 cm³ has mistaken speed for amount. Ask for a careful two-sentence comparison naming both time and total volume.

20. Temperature is a potentially important variable

Temperature influences molecular kinetic energy and can change reaction rates under suitable conditions. It can also change gas volume at a fixed amount of gas because of physical gas behaviour, complicating an interpretation based on collected volume alone.

A real fair comparison should avoid changing both temperature and reactant concentration without documenting them. The paper model stipulates comparable environmental conditions so the intended kinetic contrast remains interpretable.

21. Particle size and surface area can affect reaction rate

For reactions involving a solid, breaking the same total amount into smaller pieces may increase available surface area and influence reaction rate. The final amount of product need not increase if total reacting material and limiting conditions remain unchanged.

Some pupils assume grinding a solid creates more moles of that substance. It does not; changing particle geometry alters exposure, not necessarily the total chemical inventory. The teaching point is a controlled mechanism, not an invitation to handle reactive metal powders.

22. Catalysts provide another distinct causal mechanism

A catalyst can provide an alternative reaction pathway with a different activation energy, influencing rate while not being consumed overall in the net reaction. This is not the same as simply adding more limiting reactant.

The fictional gas-volume tables do not identify a catalyst or measure its identity. A student should not claim a catalyst was used merely because one curve is steeper; different controlled conditions could also explain the trend.

23. Pressure effects depend on reaction conditions

For some reactions involving gaseous reactants, pressure and partial pressures may influence rate. For a reaction producing gas collected in a syringe, external pressure or apparatus constraints can also affect the volume measured.

A child should not copy ‘higher pressure always faster’ into every gas collection task. The role depends on reactant state, mechanism and the conditions defined by the question.

24. A plateau does not uniquely identify the limiting reactant

An unchanged final gas volume may be consistent with chemical completion under ideal collection, but the graph alone does not specify whether the solid or liquid reagent was limiting. To identify the limiting reactant, a balanced equation and initial amounts would be required.

This distinguishes a visual observation from stoichiometric analysis. A precise-looking flat segment is not an independent chemical composition test.

25. Converting cubic centimetres to cubic decimetres

One cubic decimetre contains one thousand cubic centimetres. The 66 cm³ plateau is 0.066 dm³ or 0.066 litres. Converting the unit does not alter the total physical gas volume.

A student who writes 66 dm³ by retaining the cubic-centimetre numeric value has inflated the amount one thousandfold. The appropriate unit should follow the question rather than a memorised preference.

26. Gas volume does not automatically give moles without conditions

To turn a measured gas volume into an amount of substance, a suitable molar volume relation or gas law plus temperature and pressure information must be supplied. Our main data table contains only time and volume, not a complete thermodynamic state specification.

It would be unsupported to claim the 66 cm³ corresponds to a particular number of moles without additional stated assumptions. An advanced course can add those inputs explicitly; younger students can focus on rates and graph reading.

27. A gas collector can have systematic limitations

Real experiments may lose gas through leaks, dissolve some product into liquid, contain bubbles or have reading uncertainties. Those effects can bias cumulative volumes and make an apparent plateau misleading.

A pupil who erases an unexpected observation simply to preserve the smooth model curve is not practising good experimental reasoning. Real anomalies should lead to method checks, documented repeats and cautious interpretation.

28. A real safety procedure is not supplied here

Some gas-producing reactions can form flammable or harmful gases depending on reagents. The article offers only numerical paper data and does not instruct parents to combine acid, reactive metals or household chemicals at home.

Where Chemistry practical work is relevant, it requires school-approved equipment, qualified supervision, appropriate protective controls and assessment of the actual chemical hazards. The tutorial can teach graph analysis without performing a reaction.

29. The locality is not a source of gas-reaction measurements

NParks identifies Jalan Rajah along Whampoa Park Connector and records the wider route’s geographic details. Those public facts have no bearing on the fictional gas-volume readings and do not describe chemical emissions or air quality at nearby residences.

An article for parents should not imply that a teaching experiment measured pollution or gas release on a public path. Real environmental claims require separate verified field observations.

30. An unfamiliar interval-rate exercise tests learning

Give a new imaginary table showing 0, 18, 32, 40 and 44 cm³ at 0, 15, 30, 45 and 60 seconds. The interval averages are 18/15=1.20, 14/15≈0.933, 8/15≈0.533 and 4/15≈0.267 cm³/s.

A student who calculates these unaided has learned to subtract successive cumulative readings rather than copy the prior twenty-second intervals. Ask for an evidence-bounded description of the overall trend.

31. A complete conclusion distinguishes process from evidence

The original imaginary experiment’s cumulative gas volume rises to 66 cm³ and then stops increasing between 100 and 120 seconds. The interval-average collection rates generally decline as the graph becomes less steep.

A strong answer labels the data as collected gas volume, gives a valid average interval rate, offers possible kinetic explanations and states what the table cannot identify, including reactant identity, exact instantaneous rates and real local air quality.

Twenty changed-case worked answers

These are original instructional examples, not official national examination questions. The student should first identify the time interval, measure the change in cumulative volume, and only then calculate a rate or interpret an explanatory mechanism.

1. The original first interval

(25−0)/(20−0)=1.25 cm³/s.

Independent check: change the elapsed interval, the starting cumulative reading or the collector’s conditions. Ask whether the answer remains a direct observation, an interval-average rate, or a chemical interpretation requiring more evidence. Units must match each quantity.

2. Twenty to forty seconds

(44−25)/(40−20)=19/20=0.95 cm³/s.

3. Forty to sixty seconds

(57−44)/20=0.65 cm³/s.

4. Sixty to eighty seconds

(64−57)/20=0.35 cm³/s.

5. Eighty to one hundred seconds

(66−64)/20=0.10 cm³/s.

6. One hundred to one hundred twenty seconds

(66−66)/20=0 cm³/s average collected-volume rate.

7. Cumulative volume at forty seconds

44 cm³ total collected, not 44 newly collected during the second interval.

8. Whole-trip average to sixty seconds

57/60=0.95 cm³/s across 0–60 s; this is not the 40–60 s interval average.

9. The plateau

66 cm³ in the model, not proof of exact molecular completion.

10. Convert plateau to litres

66 cm³=0.066 litres under exact metric volume conversion.

11. Faster model, first twenty seconds

(40−0)/20=2.0 cm³/s.

12. Compare first-interval averages

2.0/1.25=1.6, a ratio of two imagined average collection rates.

13. Shared final yield

Both model treatments end at 66 cm³ despite different rate curves.

14. Faster model plateau time

The faster curve is already flat in its 60–80 s data interval.

15. Unknown limiting reagent

A gas-volume plateau alone does not identify which reactant was limiting.

16. Fifteen-second altered data first segment

18 cm³ over fifteen seconds gives 1.20 cm³/s.

17. Altered second segment

32−18=14 cm³ in fifteen seconds, about 0.933 cm³/s.

18. Gas measurement limitation

Leaks or dissolution can alter collected volume independently of intrinsic chemical rate.

19. Rate and amount units

Rate has cm³/s, while total collected volume has cm³.

20. Source limit

No gas measurement was made in Jalan Rajah or Whampoa Park Connector.

A ninety-minute tutorial with three different learners

Time	Teaching purpose	Personal evidence
0–10 minutes	Unaided recall of the last marked kinetics question	Student’s first decision
10–25 minutes	Diagnose endpoint, unit or graph-slope confusion	One specific correction
25–45 minutes	Explain interval-average gas-volume rate	Student reconstructs two subtractions
45–65 minutes	Three different reaction-curve questions	Individual corrections
65–80 minutes	Unlabelled new rate table and limitation	Independent method selection
80–90 minutes	Error log and spaced retrieval problem	A manageable next learning task

Illustrative small-group teaching framework, not a fixed timetable.

One teenager may need help subtracting cumulative readings, another might need a collision-theory explanation, and a third can challenge a claim about reaction completion. The tutor can teach a shared core while checking those different understanding levels separately rather than asking everyone to copy a single perfect graph.

Four weeks of diagnosis, repair and transfer

Week 1 — Diagnose. Use an actual marked graph and an unseen new interval to locate the first wrong inference or operation.
Week 2 — Rebuild. Explain cumulative volume, interval slopes and a plateau, then apply the method to a changed curve.
Week 3 — Interleave. Put an unfamiliar reaction-rate table among other Science data items and remove headings that reveal the formula.
Week 4 — Retrieve. Return after several days with different collection times, requiring independent calculation and evidence-bound explanation.

A fixed four-week timetable is not a promise of grade improvement. A responsible tutor adjusts how an idea is taught if the learner still needs cues and moves to a more useful topic once independent understanding is secure. Schoolwork, sleep and practical travel time remain important.

Singapore secondary Science pathways and the 2027 transition

MOE’s Full Subject-Based Banding explanation describes different G1, G2 and G3 subject levels. Reaction-rate calculations and practical depth belong to the student’s actual Chemistry course and current school sequence, rather than being compulsory for every Secondary 3 student.

SEAB confirms the SEC begins in 2027. Candidates examined in 2026 use their applicable GCE syllabuses; the 2027 G2, and 2027 G3 directories list Chemistry-containing Science routes with different scope. For 2027, G2 includes K223 and K225 with Chemistry, while G3 includes Chemistry K324 and combined options K326 and K328. None of these synthetic tasks is a copied specimen-paper question.

Jalan Rajah and real-world chemical safety are separate matters

NParks’ official Whampoa Park Connector description identifies Jalan Rajah as part of the route. The park’s locality has not been used as a source of gas volumes, reaction-rate measurements or air quality evidence in this article.

Gas-producing reactions can be hazardous. Students should not use the example to make or collect gases at home; approved practical work requires trained school supervision and safety precautions. The original calculations are complete with a printed table.

Frequently asked questions

Is cumulative gas volume the same as reaction rate?

No. A rate requires a change in volume over a specified change in time.

How is an interval-average rate calculated?

Subtract the beginning volume from the end volume, then divide by the duration of that interval.

Does a plateau always prove the limiting reagent was used up?

No. Collection limitations or other factors could also produce a plateau.

Can two reactions have the same total gas but different speeds?

Yes. The two fictional models reach the same 66 cm³ with different time profiles.

Does this provide a safe home chemistry experiment?

No. The guide is paper-only and does not authorise reactive gas generation.

Was air near Jalan Rajah tested?

No. All figures are invented classroom observations.

Is this exact topic required in all Science subject combinations?

No. Check the student’s Chemistry component and applicable school assessment.

What evidence of progress should parents request?

An independently calculated interval rate and a cautious explanation for a new curve.

Continue all Jalan Rajah Secondary Science guides

Secondary 1 Science Tuition | Jalan Rajah Weekday or Weekend Parent Dilemma
Secondary 2 Science Tuition | Jalan Rajah Weekday or Weekend Parent Dilemma
Secondary 3 Science Jalan Rajah — this guide
Secondary 4 Science Tuition | Jalan Rajah Weekday or Weekend Parent Dilemma

Official references and consultation

Bring recent marked Science work, the student’s selected Chemistry subject level and a practical weekday/weekend plan to an eduKate parent–student consultation. The learning goal is an accurate unseen rate question answered without prompts.

1. Compare two curves at the same elapsed time

At sixty seconds the original fictional treatment shows 57 cm³ collected gas while the faster-condition treatment has 66 cm³. The nine-cubic-centimetre difference at that instant does not imply nine more moles or a permanent yield difference. The original treatment later reaches the same sixty-six-cubic-centimetre plateau.

Ask whether the faster treatment changed its final product quantity or merely reached the illustrated final volume earlier. The child should use both graph endpoints and time coordinates before answering.

2. Compare one interval across two treatments

From twenty to forty seconds, the original model adds 19 cm³ gas, giving an average 0.95 cm³/s. The faster treatment adds 19 cm³ over the same interval too, giving 0.95 cm³/s, even though its cumulative level is higher at both endpoints.

This counterexample shows that two curves can have equal interval-average slopes at one time window and different overall histories. A student who ranks rates solely by curve height would get this wrong.

3. Do not confuse a ratio of volumes with a ratio of rates

At twenty seconds, original and faster cumulative volumes are 25 and 40 cm³, a ratio of 1.6. Their first-interval average rates happen also to have a ratio of 1.6 only because both start at zero and share the same twenty-second window. At later windows, that numeric coincidence need not continue.

Ask for the interval from forty to sixty seconds: original gains 13 cm³, faster gains 7 cm³. Their average rates have a different ratio, so a universal 1.6 speed factor would be unsupported.

4. Plot two rate tables instead of just one cumulative table

A rate-versus-time plot can use interval midpoints (10,30,50,70,90,110 seconds) and the original model’s corresponding twenty-second interval-average rates of 1.25,0.95,0.65,0.35,0.10,0 cm³/s. The point at midpoint is a representation of an interval mean, not a directly measured instantaneous rate.

This distinction teaches how derived plots are constructed. A pupil should label them as ‘mean rate for each interval’ rather than claim the collector reported the instantaneous rate exactly at each midpoint.

5. A new plateau does not establish a gas identity

If an invented sample stops producing measurable collected volume, the gas could be one of several possible products depending on the reaction. The numerical shape contains no spectral, chemical or qualitative gas test information that uniquely identifies the product.

The tutor should ask what additional evidence would identify the reactants and products. This avoids dangerous speculation and reinforces that the paper task measures only changes in a recorded gas volume.

6. A changed table with unequal intervals

An imaginary reaction collects 0,12,27 and 33 cm³ at times 0,10,25 and 55 seconds. Its interval average rates are 12/10=1.20,15/15=1.00 and 6/30=0.20 cm³/s. The varying interval durations must each be used instead of a memorised twenty seconds.

A child who divides every change by ten because the first interval lasted ten seconds has learned an example instead of a method. This changed task makes genuine transfer visible.