IB myp 4-5 Chemistry – Practice Questions- All Topics
Topic :Matter-Particle/Kinetic theory
Topic :Matter- Weightage : 21 %
All Questions for Topic : states and properties of matter,particle/kinetic theory,diffusion,atomic structure [including isotopes],electron configuration and valency
Question (16 marks) – Investigating Frozen Desserts
Background:
One of the main ingredients of frozen desserts is milk. Milk is a solution of protein, fats and other substances in water. When frozen, the water forms ice crystals that trap other ingredients.
a. (2 marks) Draw diagrams showing the arrangement of at least 10 water molecules:
• Before freezing (liquid) • After freezing (solid)
▶️ Answer & Explanation
Answer:
• Liquid: Random arrangement, molecules touching but not ordered
• Solid: Regular hexagonal pattern, fixed positions
Explanation: Liquid water has no fixed structure while ice forms a crystalline lattice due to hydrogen bonding at 104.5° angles.
b. (2 marks) A microscope image shows an ice crystal (A) with scale bar 20 µm. Convert this measurement to meters in standard form.
▶️ Answer & Explanation
Answer: 2.0 × 10-5 m
Solution: 20 µm = 20 × 10-6 m = 2.0 × 10-5 m
c. (4 marks) Graph this ice cream freezing data:
| Temperature (°C) | % Frozen |
|---|---|
| -2.50 | 0 |
| -3.00 | 20 |
| -4.50 | 40 |
| -7.00 | 60 |
| -15.00 | 80 |
▶️ Answer & Explanation
Requirements:
• Properly labeled axes (Temperature vs % Frozen)
• Correct scale for both axes
• All 5 points accurately plotted
• Smooth curve connecting points
d. (2 marks) Using your graph, estimate the temperature at 50% frozen.
▶️ Answer & Explanation
Answer: -6.0 ± 0.5°C
Method: Interpolate between -4.5°C (40%) and -7.0°C (60%)
e. (3 marks) Liquid nitrogen (-196°C) makes smoother ice cream than conventional freezing. Formulate a hypothesis.
▶️ Answer & Explanation
Answer:
If: Freezing temperature decreases
Then: Ice crystal size decreases
Because: Faster freezing prevents large crystal growth
f. (1 mark) Melting time data for 2cm cubes:
| Substance | Melting Time | ||
|---|---|---|---|
| Soda | 45:54 | 38:02 | 44:45 |
| Water | 42:31 | 48:56 | 43:22 |
| Milk | 62:00 | 66:00 | 58:34 |
Suggest one data presentation improvement.
▶️ Answer & Explanation
Answer: Calculate averages / Use consistent time units / Add error bars
Reason: Raw trial data is harder to compare than processed statistics.
g. (2 marks) The hypothesis was: “Milk cubes melt fastest.” Does the data support this?
▶️ Answer & Explanation
Answer: No – milk melted slowest (water was fastest).
Evidence: Milk times >60 min vs water ~45 min.