מדע: סיכומי מחקר, בקרות ומבחני הנדסה
הוצג| English | משמעות |
|---|---|
| criterion/kraɪˈtɪərɪən/ | A rule used to decide or judge something. |
| controlled variable/kənˈtrəʊld ˈveərɪəbl/ | משתנה מבוקר |
Three experiments, one question
- A research summary describes Experiment 1 (changing temperature), Experiment 2 (changing light) and Experiment 3 (changing both) on how fast seeds sprout.
- ACT asks you to identify variables and controls in each experiment and to pick a follow-up test that isolates an explanation.
Variables in each experiment
- In each experiment, find what was changed (independent), what was measured (dependent) and what was kept the same (controlled).
- Compare experiments: if only light changes in Experiment 2, any difference in sprouting time is linked to light.
In Experiment 2, seeds are kept at 20 °C under 4, 8 or 12 hours of light, and days to sprout are recorded. What is the dependent variable?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Days to sprout is measured.
Isolate one explanation
- A good follow-up changes one variable at a time and keeps everything else the same.
- To test whether soil type matters, grow the same seeds at the same temperature and light, changing only the soil.
Scientists think a fertiliser speeds growth, but the fertilised plants were also watered more. Best follow-up: two groups with equal water, one with fertiliser and one without.
Fair test or not?
Recognise follow-up experiments that isolate one variable.
A student thinks music helps plants grow, but the plants with music were also kept near a window. Which follow-up best tests the music idea?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Only music differs between the groups.
A fair test changes only ____ variable at a time.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Everything else is controlled.
Engineering tests
- Engineering summaries compare designs against criteria (strength, cost, weight). Read which design meets all stated requirements, not just the best in one column.
- Trade-offs are common: the strongest bridge model may also be the heaviest.
A bridge must hold at least 50 N and weigh under 200 g. Model A: holds 80 N, 250 g. Model B: holds 55 N, 180 g. Model C: holds 45 N, 120 g. Which meets both requirements?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Only B is strong enough and light enough.
Traps
- Two variables changed at once: you cannot tell which caused the result.
- Best in one criterion 标准: a design must satisfy every requirement in the question.
Changing temperature and light at the same time makes it impossible to tell which caused the result.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
True. With two variables changed together, their effects cannot be separated; change one at a time.
Recap
- For each experiment, list changed, measured and controlled variables 控制变量.
- A fair follow-up changes one variable; engineering choices must meet all criteria.
- criterion: A rule used to decide or judge something.
- controlled variable: A factor kept the same in an experiment so that the test is fair.