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Grade 9: Science subject test

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1. A selective membrane passes water but not the supplied solute; passive water entry changes model cell volume. What fits? Which inference or prediction is best supported?Osmosis is unrelated to passive water diffusion.Volume change alone identifies every transport mechanism.Osmotic water movement can alter volume without pumping the solute.Water entry proves solute crossed the membrane.

2. Supplied case 6: higher concentration (mmol/L)=30; lower concentration (mmol/L)=12, using the explicitly named quantities. Concentration difference equals higher millimoles per liter minus lower millimoles per liter. What result follows?17 mmol/L18 mmol/L42 mmol/L19 mmol/L

3. A pump consumes energy to maintain unequal concentrations and steady counts. What is warranted? Which inference or prediction is best supported?A maintained steady state is not passive equal-concentration equilibrium.Stable counts prove all flows stopped.Unequal concentrations are impossible with pumping.A pump creates the solute atoms.

4. A model adds folds to its boundary without changing interior volume. What is predicted? Which inference or prediction is best supported?Volume must increase by the same amount as area.Every fold creates new atoms.A greater ratio guarantees every transport pathway works faster.Area/volume rises, increasing the modeled exchange surface per interior volume.

5. A model has RNA carrying sequence information and an enzyme catalyzing a reaction. What distinction fits? Which inference or prediction is best supported?Only one molecular group can exist per cell.Nucleic-acid information and protein-catalysis roles can coexist.Every RNA molecule is the same as that enzyme.The enzyme necessarily stores all hereditary information.

6. An enzyme remains after repeated model reactions while products accumulate. What is supported? Which inference or prediction is best supported?It can catalyze multiple cycles rather than being consumed as the product.Every cycle creates a new enzyme from nothing.An enzyme is always permanently used up in one event.Reuse proves activity is independent of conditions.

7. Supplied case 6: product model-molecule count=84; duration (s)=7, using the explicitly named quantities. Average product rate equals product molecules in model count divided by seconds. What result follows?588 model molecules/s13 model molecules/s11 model molecules/s12 model molecules/s

8. Temperature and acidity both change between enzyme trials. What is warranted? Which inference or prediction is best supported?Acidity cannot affect any enzyme.The result proves a universal temperature optimum.The rate difference cannot be uniquely attributed to temperature.More changes always strengthen single-variable causation.

9. A supplied sugar stores chemical energy captured during photosynthesis. What happens when it later supports respiration? Which inference or prediction is best supported?Energy is transferred/transformed while atoms are rearranged.Energy is an extra carbon atom.The sugar’s atoms must be destroyed.Every unit of usable energy cycles unchanged forever.

10. A plant’s respiration model uses oxygen and returns CO₂. What inference follows? Which inference or prediction is best supported?Oxygen use proves the plant is an animal.Respiration can occur only in roots.Carbon atoms are necessarily destroyed by oxygen.Plants can respire as well as photosynthesize.

11. Supplied case 6: modeled glucose-molecule count=8, using the explicitly named quantities. Carbon-dioxide molecules required equal six times modeled glucose molecules. What result follows?49 CO₂ molecules47 CO₂ molecules48 CO₂ molecules14 CO₂ molecules

12. An ecosystem returns carbon to its earlier chemical form while energy disperses as heat. What follows? Which inference or prediction is best supported?Carbon atoms disappear when heat leaves.Matter cycling does not mean usable energy cycles indefinitely.All heat automatically returns as the original sunlight.No new energy input is needed.

13. The plot record includes only oak individuals of one species. What does adding insects and soil data change? Which inference or prediction is best supported?It remains only an oak population in every sense.Soil data alone is a new species.Multiple organisms prevent ecological analysis.It broadens beyond one population toward community/ecosystem information.

14. Supplied case 6: counted individuals=84; sampled area (m²)=14, using the explicitly named quantities. Sample density equals counted individuals divided by sampled square meters. What result follows?7 individuals/m²5 individuals/m²6 individuals/m²1176 individuals/m²

15. Two species use the same limited nesting holes; added holes reduce the conflict. What mechanism fits? Which inference or prediction is best supported?Competition requires the organisms to be identical species.Resource competition can weaken when the limiting resource increases.Sharing a limited resource always proves mutualism.Added holes eliminate every ecological limit.

16. Counts rise after observers switch to a method detecting hidden animals better. What is demonstrated? Which inference or prediction is best supported?Higher recorded counts, with population growth still confounded by detection change.Population growth is proved solely by the increase.Detection methods never affect counts.The animals must have reproduced during observation.

17. A neutral atom gains two electrons without changing its nucleus. What net charge follows? Which inference or prediction is best supported?Zero because nuclei alone determine charge.A new element must form.−2 in units of elementary charge.+2 because electrons are positive.

18. Supplied case 6: isotope mass number=40; atomic number=20, using the explicitly named quantities. Neutron count equals mass number minus atomic number. What result follows?19 neutrons20 neutrons60 neutrons21 neutrons

19. A particle has 12 protons and 10 electrons. What is warranted? Which inference or prediction is best supported?It has net charge+2; missing electrons do not change the 12-proton element identity.It is neutral because neutrons are unknown.It has charge−2.It became a 10-proton element.

20. Two main-group elements share a column but lie in different periods. What is supported? Which inference or prediction is best supported?They must be the same element.Every isotope mass is identical.Group membership guarantees every reaction result.Related valence patterns can suggest trends, but properties need not be identical.

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