- Solve a situation task in the order data, law, calculation, conclusion
- Convert units and check whether an answer is reasonable
- Find genotype and phenotype ratios in a genetic cross
Aysel wants to be a doctor and Elvin an engineer. Both have science subjects in the second stage: in group IV biology and chemistry have coefficient 1.5 and physics 1; in group I physics has 1.5 and chemistry (in the RK subgroup) 1. In these subjects most points come from a well-built solution: recognising the law, converting units and writing the conclusion clearly.
| Subject | Group and coefficient | Basis of the written tasks |
|---|---|---|
| Physics | I — 1.5; IV — 1 | a situation in group IV |
| Chemistry | I (RK) — 1; IV — 1.5 | a situation in group IV |
| Biology | IV — 1.5 | a situation |
| Geography | II — 1.5; III (TC) — 1 | a situation |
Situation tasks: five steps
- 11. Data
Write every quantity from the situation with its unit and convert to SI (g → kg, cm → m, min → s).
- 22. Law
Which law or formula applies? Write it down by name.
- 33. Calculation
Solve with letters first, then substitute the numbers — this reduces mistakes.
- 44. Check
Is the unit right? Is the answer reasonable (water in a kettle cannot reach 1000 °C)?
- 55. Conclusion
Answer the situation's question in a full sentence. A partial solution can also earn points under the criteria, so write the steps you know.
- Q = c · m · Δtheat needed for heating (J); c — specific heat capacity, Δt — temperature change
- 1/R = 1/R₁ + 1/R₂1/R = 1/R₁ + 1/R₂total resistance of two resistors in parallel
- n = m / Mn = m / Mamount of substance (mol); M — molar mass (g/mol)
- ωmass fraction of the solute; m(solution) = m(solute) + m(solvent)
1) A body falls freely from rest. How far does it fall in 2 s (g = 10 m/s²)?
A) 10 m B) 20 m C) 40 m D) 5 m E) 2 m
2) (Coded) Resistors of 6 Ω and 3 Ω are connected in parallel to a 12 V source. What is the total current in amperes?
3) (Situation) Leyla heats 2 kg of water in an electric kettle from 20 °C to 70 °C. c = 4200 J/(kg · °C). a) How much heat does the water need? b) If the kettle's power is 2000 W and there are no losses, how long will it take?
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2) 1/R = 1/6 + 1/3 = 1/2 → R = 2 Ω. Ohm's law: I = U / R = 12 / 2 = 6 A.
3) a) Δt = 70 − 20 = 50 °C; Q = c · m · Δt = 4200 · 2 · 50 = 420 000 J = 420 kJ.
b) Q = P · t → t = Q / P = 420 000 / 2000 = 210 s = 3.5 min.
Conclusion: heating the water takes 420 kJ of heat and 3.5 minutes.
4) (Coded) How many moles are in 49 g of sulfuric acid (H₂SO₄)? Ar(H) = 1, Ar(S) = 32, Ar(O) = 16.
5) 20 g of salt is dissolved in 180 g of water. What is the mass fraction of salt in the solution?
A) 11.1% B) 20% C) 10% D) 9% E) 18%
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5) m(solution) = 20 + 180 = 200 g; ω = 20 / 200 · 100% = 10% → C. 11.1% (20 / 180) is the trap for those who divide by the water: the denominator is always the mass of the solution.
6) In a family both parents have normal skin pigmentation, but both carry the albinism gene (Aa). Albinism is a recessive trait. a) What will the ratio of the children's genotypes be? b) What is the probability of an albino child, in percent? Justify your answer.
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a) Genotypes: 1 AA : 2 Aa : 1 aa. Phenotypes: 3 normal : 1 albino.
b) Albinism shows only in aa (a recessive trait): the probability is 1/4 = 25%.
Conclusion: for each child the chance of albinism is 25%; this does not mean that exactly one child in four will be albino.
Find the theory and many more problems in Educora's Physics, Chemistry and Biology courses; there are also Geography for groups II and III (TC) and Computer Science for the Rİ subgroup.
Key points
- In group IV biology and chemistry have coefficient 1.5; the written physics and chemistry tasks are situation-based.
- Situation: data → law → calculation → check → conclusion.
- In a mass fraction the denominator is the solution's mass; in parallel circuits you add the 1/R values.
- Aa × Aa: genotypes 1:2:1, phenotypes 3:1, a 25% chance of the recessive trait.
Check yourself
10 questions. Every correct answer earns XP.