Scientific Study: Variables, Units, and Methodology

Posted on Jul 7, 2026 in Chemistry

Scientific Study: Very Short Questions

1. (2081 Koshi Q.No. 2a)
   Dependent variable: Solubility of salt.
2. What is the dependent variable in throwing a stone with a stretched rubber band?
   Answer: Distance travelled by the stone.
3. Write the fundamental units included in the unit of force.
   Answer: Kilogram (kg), metre (m), and second (s).
4. Write a difference between fundamental unit and derived unit.
   Answer: Fundamental units are independent, whereas derived units are formed from fundamental units.
5. Define controlled variable.
   Answer: A controlled variable is a variable that is kept constant throughout an experiment.
6. What is a unit?
   Answer: A unit is a standard quantity used to measure a physical quantity.
7. Why should we control some of the variables during research study?
   Answer: To obtain fair, accurate, and reliable results.
8. What is scientific study?
   Answer: Scientific study is the systematic investigation of a problem using the scientific method.
9. Why is scientific study important?
   Answer: It provides reliable and evidence-based knowledge.
10. What are the steps involved in a scientific study?
    Answer: Observation, hypothesis, experiment, data collection, analysis, and conclusion.
11. Write any one principle of scientific study.
    Answer: Objectivity.
12. Write any one difference between qualitative and quantitative research.
    Answer: Qualitative research deals with descriptions, whereas quantitative research deals with numerical data.
13. How do scientists gather data for scientific study?
    Answer: By observation, experiments, and measurements.
14. How is scientific study used in different fields?
    Answer: It is used to solve problems and develop new knowledge in different fields.
15. Write a common challenge of scientific study.
    Answer: Controlling variables.
16. How is scientific study communicated to the public?
    Answer: Through scientific journals, reports, and presentations.
17. What is an independent variable?
    Answer: An independent variable is the variable that is changed or manipulated by the researcher.
18. What is a dependent variable?
    Answer: A dependent variable is the variable that changes in response to the independent variable.
19. What are the basic units in scientific measurement?
    Answer: Fundamental (SI) units.
20. Define fundamental unit.
    Answer: A fundamental unit is an independent unit that cannot be expressed in terms of other units.
21. Define derived unit.
    Answer: A derived unit is a unit obtained by combining fundamental units.

Scientific Study: Short Questions

1. Check the correctness of the equation s = ut + ½at² by unit-wise analysis.
   LHS: [s] = m
   RHS: [ut] = (m/s) × s = m; [at²] = (m/s²) × s² = m
   Since both terms on the RHS have the unit of metre (m), the equation is valid.
2. Prove that the fundamental unit of power is kg·m²·s⁻³.
   Power = Work / Time
   Work = Force × Distance
   Force = kg·m·s⁻²
   Therefore, Power = (kg·m·s⁻² × m) / s = kg·m²·s⁻³.
3. What are the dependent and independent variables when a piece of paper is thrown with a stretched rubber band?
   Independent variable: Stretch of the rubber band.
   Dependent variable: Distance travelled by the paper.
4. Test the validity of v² = u² + 2as by unit-wise analysis.
   LHS: [v²] = (m/s)² = m²/s²
   RHS: [u²] = (m/s)² = m²/s²; [2as] = (m/s²) × m = m²/s²
   Both sides have the same unit. Therefore, the equation is valid.
5. Define fundamental unit and give one example.
   A fundamental unit is an independent unit that cannot be expressed in terms of other units. Example: Kilogram (kg).
6. Name a dependent and an independent variable for plant growth in lighted and dark rooms.
   Independent variable: Amount of light.
   Dependent variable: Growth rate of the plant.
7. Prove that the unit of gravitational constant is a derived unit.
   Formula: F = (GMm) / r²
   G = (F × r²) / (Mm)
   Unit of G = ((kg·m·s⁻²) × m²) / kg² = m³·kg⁻¹·s⁻². This is a derived unit.
8. Plant growth and availability of sunlight.
   Independent variable: Availability of sunlight.
   Controlled variable: Water supplied to the plant.
9. Pulley experiment.
   Controlled variable: Load of the object (or type of pulley).
   Dependent variable: Effort applied.
10. What aspects should be considered about variables during scientific research? (Any two)
    
    • Change only one independent variable at a time.
    • Keep controlled variables constant.
11. What is unit-wise analysis? Explain its concept and importance.
    It compares the units of both sides of an equation. It checks whether the equation is dimensionally correct and helps detect mistakes in scientific formulas.
12. How do controlled variables affect the validity of results?
    They ensure a fair test and improve the accuracy and reliability of results.
13. Give examples of independent, dependent, and controlled variables.
    Independent variable: Amount of sunlight.
    Dependent variable: Plant growth.
    Controlled variable: Water given to the plant.
14. How do scientists ensure measurements are correct and reliable?
    They use standard SI units, calibrated instruments, and repeat measurements to record data carefully.
15. Limitations of scientific research in controlling variables.
    Some variables cannot be completely controlled, environmental factors may affect results, and human or instrument errors may occur.
16. Flow chart of scientific study.
    Observation → Problem Identification → Hypothesis → Experiment → Data Collection → Data Analysis → Conclusion → Communication of Results.
17. How are fundamental units used to derive units?
    Derived units are formed by multiplying or dividing fundamental units. Example: Force = kg·m·s⁻².
18. Test the validity by unit-wise analysis.
    (a) v² = u + at: LHS = m²/s²; RHS = m/s + (m/s² × s) = m/s. Units are not equal. Not valid.
    (b) s = ut + ½at²: LHS = m; RHS = (m/s × s) + (m/s² × s²) = m + m = m. Valid.
    (c) v² = u² + 2as: LHS = m²/s²; RHS = m²/s² + (m/s² × m) = m²/s². Valid.
    (d) p = mv²: LHS (Momentum) = kg·m·s⁻¹; RHS = kg × (m/s)² = kg·m²·s⁻². Units are not equal. Not valid.
19. Prove the following units.
    (i) Force: Mass × Acceleration = kg × m/s². Unit: Newton (N) = kg·m·s⁻².
    (ii) Pressure: Force / Area = (kg·m·s⁻²) / m² = kg·m⁻¹·s⁻². Unit: Pascal (Pa).
    (iii) Power: Work / Time = (Force × Distance) / Time = (kg·m·s⁻² × m) / s = kg·m²·s⁻³. Unit: Watt (W).
    (iv) Electric Resistance: Voltage / Current. Voltage = Power / Current = (kg·m²·s⁻³) / A = kg·m²·s⁻³·A⁻¹. Resistance = (kg·m²·s⁻³·A⁻¹) / A. Unit: Ohm (Ω) = kg·m²·s⁻³·A⁻².

Differences Between Scientific Concepts

20. Independent Variable vs. Dependent Variable

21. Fundamental Unit vs. Derived Unit

22. Fundamental Quantities vs. Derived Quantities

Scientific Reasoning and Justifications

23. Scientific study is considered the most reliable form of inquiry.
    It is based on observation, experimentation, and evidence. Its results can be tested and verified by others.
24. The controlled variable is kept constant in an experiment.
    To ensure that only the independent variable affects the result and to obtain accurate and reliable results.
25. SI units are used in scientific research.
    They provide a universal standard of measurement and make scientific results accurate and comparable worldwide.
26. The unit of work (Joule) is a derived unit.
    Joule is obtained from fundamental units: kg·m²·s⁻². Therefore, it is formed by combining fundamental units.
27. The independent variable is manipulated in an experiment.
    To observe its effect on the dependent variable and to test the relationship between variables.

Scientific Study: Long Questions

1. Find the independent and dependent variables.
   (i) More growth of plant in sunlight: Independent variable: Amount of sunlight; Dependent variable: Growth of the plant.
   (ii) Stretch of a catapult and distance covered: Independent variable: Stretch of the catapult; Dependent variable: Distance travelled by the stone.
2. Medium of light and refractive index.
   Independent variable: Medium of light.
   Dependent variable: Refractive index.
   Changing the medium changes the refractive index. Different media have different refractive indices; therefore, the refractive index depends on the medium.
3. Differentiate between independent and dependent variables. Identify the variables.
   Differences: The independent variable is changed by the researcher (cause), while the dependent variable changes due to the independent variable (measured effect).
   Identification:
   (i) Force applied to stretch a rubber band: Independent: Force applied; Dependent: Stretch of the rubber band.
   (ii) Distance travelled by a stone thrown: Independent: Stretch of the rubber band; Dependent: Distance travelled by the stone.
4. Prove that Watt is a derived unit and check the unit-wise homogeneity of s = ut + ½at².
   (a) Prove Watt is a derived unit: Power = Work / Time. Work = Force × Distance. Force = kg·m·s⁻². Therefore, Power = (kg·m·s⁻² × m) / s = kg·m²·s⁻³. Hence, Watt (W) = kg·m²·s⁻³, so it is a derived unit.
   (b) Unit-wise homogeneity: LHS: [s] = m. RHS: [ut] = (m/s) × s = m; [at²] = (m/s²) × s² = m. Both sides have the unit metre (m). Therefore, the equation is unit-wise homogeneous (valid).
5. Define variables in scientific study. Explain its types with examples.
   Variables: Factors that can change during an experiment.
   Types:
   
   • Independent variable: The variable changed by the researcher. Example: Amount of sunlight.
   • Dependent variable: The variable measured in response. Example: Plant growth.
   • Controlled variable: The variable kept constant. Example: Water, soil, and type of plant.
6. Variables involved in a bowling event.
   (i) Different variables involved: Independent, Dependent, and Controlled variables.
   (ii) Categorization: Independent: Speed or force of bowling; Dependent: Distance or movement of the ball; Controlled: Pitch condition, type of ball, and weather.
7. Catapult experiment.
   (i) Different variables: Independent: Stretch of the rubber band (5 cm and 8 cm); Dependent: Distance travelled by the paper; Controlled: Same paper, same catapult, and same throwing angle.
   (ii) Relationship: As the stretching of the rubber band increases, the distance travelled by the paper also increases. Thus, the dependent variable increases with the independent variable.
8. What is the SI system? Why was it developed?
   SI System: The SI (International System of Units) is the internationally accepted standard system of measurement.
   Why it was developed: To provide a universal standard of measurement, avoid confusion caused by different unit systems, ensure accurate and uniform scientific measurements, and make scientific communication easier throughout the world.