Bio lab 1-3

Q1. What is the part of the microscope you look through to see the specimen?
A1. Ocular lens (eyepiece).

Q2. Which microscope part adjusts the amount of light passing through the specimen?
A2. Diaphragm.

Q3. Which knob moves the stage in large steps vs small steps?
A3. Coarse adjustment (large steps), Fine adjustment (small steps).

Q4. What happens to the field of view as magnification increases?
A4. It decreases (you see less area but in more detail).

Q5. What happens to depth of focus as magnification increases?
A5. It decreases; only thin slices are in focus at once.

Q6. Define magnification.
A6. The enlargement of an image using ocular and objective lenses.

Q7. Define field of view.
A7. The circular area visible through the microscope.

Q8. If the ocular lens is 10x and the objective is 40x, what is total magnification?
A8. 400x.

Q9. Who invented the first simple microscope and what did he observe?
A9. Anton van Leeuwenhoek; observed “animalcules” (microorganisms).

Q10. Who coined the term “cell”?
A10. Robert Hooke, while observing cork cells.

Q11. List the correct order of viewing a specimen under the microscope.
A11. Start with 4x + stage up → place slide → coarse focus → switch to 10x → fine focus → switch to 40x → fine focus → reset to 4x → turn off light.

Q12. Why is lab safety important?
A12. Prevents contamination, protects people and equipment, ensures valid results.

Q13. Example of independent, dependent, and control group in an experiment?
A13. Independent = variable manipulated; Dependent = what changes in response; Control = baseline group for comparison.

Q14. What is a scientific theory vs scientific principle?
A14. Theory = supported explanation based on evidence; Principle = widely accepted, established scientific truth.

🧪 Lab 2 – Chromatography & Measurements

Q15. What is chromatography used for?
A15. To separate mixtures into their individual components.

Q16. What are the stationary and mobile phases in paper chromatography?
A16. Stationary = paper; Mobile = solvent.

Q17. Define Rf value.
A17. Distance traveled by solute ÷ distance traveled by solvent (from baseline).

Q18. What does it mean if two dyes have the same Rf value?
A18. They are likely the same substance.

Q19. Why is X considered a pure substance while Y and Z are mixtures in chromatography?
A19. X produces one spot, Y and Z produce multiple.

Q20. If Rf for dye A = 0.8 and dye B = 0.3, which is more soluble?
A20. Dye A (higher Rf = moved farther in solvent).

Q21. Name two factors that influence migration in chromatography.
A21. Solubility in solvent and size of solute molecules.

Q22. What is the independent and dependent variable in chromatography?
A22. Independent = solvent (mobile phase); Dependent = distance traveled by solute.

Q23. Convert 7 × 10⁻¹ mm into meters.
A23. 0.0007 m (7 × 10⁻⁴ m).

Q24. What are the base units of the metric system for: length, mass, volume, time, temperature, amount of substance?
A24. Meter (m), Gram (g), Liter (L), Second (s), Kelvin (K), Mole (mol).

Q25. Difference between accuracy and precision?
A25. Accuracy = closeness to true value; Precision = consistency of repeated measurements.

⚛ Lab 3 – Atoms, Water, Polarity, pH

Q26. Define an isotope.
A26. Atoms of the same element with the same # protons but different # neutrons.

Q27. Define an ion.
A27. Atom with unequal # of protons and electrons → carries a charge.

Q28. If an atom has 8 protons, 8 neutrons, and 5 electrons: neutral? ion? stable?
A28. Not neutral, it’s a positive ion (more protons than electrons), not stable (valence not filled).

Q29. Define polar covalent bond.
A29. Bond where electrons are shared unequally due to differences in electronegativity.

Q30. What causes partial charges (δ⁺, δ⁻) in a molecule?
A30. Unequal sharing of electrons.

Q31. What is a polar molecule? Give an example.
A31. Molecule with unequal charge distribution; Example: water (H₂O).

Q32. What is the pH of pure water?
A32. 7 (neutral; [H⁺] = [OH⁻]).

Q33. If a solution moves from pH 6 to pH 7, what happened to H⁺ concentration?
A33. It decreased tenfold (less acidic).

Q34. Define strong acid vs weak acid.
A34. Strong acid fully dissociates in water (large Ka, low pKa). Weak acid partially dissociates (small Ka, higher pKa).

Q35. What is a buffer?
A35. A weak acid/base system that resists large pH changes by absorbing H⁺ or OH⁻.

Q36. What is the role of phenolphthalein in titration?
A36. pH indicator: colorless in acid, pink in base.

Q37. Why doesn’t pH rise immediately in titration of acetic acid with NaOH?
A37. Added OH⁻ neutralizes H⁺ from acetic acid first; pH rises only after equivalence point.

Q38. What is the equivalence point in titration?
A38. Point where moles of acid = moles of base; solution shifts sharply in pH.

Q39. What happens if more NaOH is added beyond equivalence point?
A39. Excess OH⁻ makes solution more basic → pH rises sharply.

Q40. On a titration graph, which is the independent variable (x-axis) and dependent (y-axis)?
A40. Independent = volume of NaOH; Dependent = pH.