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📕 For All Grade 9- 12 students 📚
Entrance ተፈታኝ ተማሪዎችን ለማገዝ ተብሎ የተከፈተ ምርጥ ቻናል እንጠቁማችሁ
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### Phase Change and Calorimetry
Phase Change refers to the transition of matter from one state (solid, liquid, gas) to another. The main types of phase changes include:
- Melting: The process of a solid turning into a liquid when heat is added.
- Freezing: The transition from liquid to solid as heat is removed.
- Vaporization: The conversion of a liquid into gas, which occurs at boiling point when heat is added. It can happen through:
- Evaporation: Surface-level vaporization at any temperature.
- Boiling: Rapid vaporization throughout the liquid at a specific temperature.
- Condensation: The process of gas turning into liquid when heat is removed.
- Sublimation: The transition from solid directly to gas without passing through the liquid state (e.g., dry ice).
- Deposition: The reverse of sublimation, where gas turns directly into solid.
Calorimetry is the science of measuring the amount of heat released or absorbed during a chemical reaction or phase change. A calorimeter is the device used for this purpose. Key concepts include:
- Specific Heat Capacity (c): The amount of heat required to raise the temperature of one gram of a substance by one degree Celsius.
- Latent Heat (L): The heat absorbed or released during a phase change without a change in temperature.
- Latent Heat of Fusion (L_f): Heat required to melt a substance.
- Latent Heat of Vaporization (L_v): Heat required to vaporize a substance.
The relationship for calculating heat (q) involved in temperature change is given by:
q = mcΔ T
For phase changes:
q = mL
where:
- m is the mass,
- c is the specific heat,
- Δ T is the change in temperature,
- L is the latent heat.
### Multiple Choice Questions (MCQs)
1. What phase change occurs when ice turns into water?
- A Freezing
- B Melting
- C Condensation
- D Sublimation
Correct Answer: B Melting
2. What is the primary characteristic of a substance during a phase change?
- A Temperature change
- B Volume change
- C Pressure change
- D Constant temperature
Correct Answer: D Constant temperature
3. What is the heat absorbed in melting a substance called?
- A Latent heat of vaporization
- B Latent heat of fusion
- C Specific heat
- D Thermal energy
Correct Answer: B Latent heat of fusion
4. Which of the following is an endothermic process?
- A Freezing
- B Condensation
- C Melting
- D Deposition
Correct Answer: C Melting
5. During which phase change does a liquid become a gas?
- A Freezing
- B Melting
- C Vaporization
- D Sublimation
Correct Answer: C Vaporization
6. In calorimetry, which device is used to measure heat changes?
- A Thermometer
- B Calorimeter
- C Barometer
- D Manometer
Correct Answer: B Calorimeter
7. Heat capacity is defined as:
- A The mass of the substance
- B The heat required to raise temperature
- C The heat required to change phase
- D The temperature change
Correct Answer: B The heat required to raise temperature
8. What is the unit of heat in the SI system?
- A Joule
- B Calorie
- C Watt
- D Kelvin
Correct Answer: A Joule
9. Which substance has the highest latent heat of vaporization?
- A Water
- B Alcohol
- C Mercury
- D Oil
Correct Answer: A Water
10. What happens during condensation?
- A Solid becomes liquid
- B Liquid becomes solid
- C Gas becomes liquid
- D Liquid becomes gas
Correct Answer: C Gas becomes liquid
11. The specific heat of water is approximately:
- A 0.5 J/g°C
- B 1.0 J/g°C
- C 4.18 J/g°C
- D 2.0 J/g°C
Correct Answer: C 4.18 J/g°C
12. Which of the following phase changes requires energy input?
- A Freezing
- B Condensation
- C Melting
- D Deposition
Correct Answer: C Melting
13. What is the result of applying heat to a solid?
- A It will a
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CBT እና PPBT ምንድነ ነው?
- CBT ማለት በእንግሊዘኛው Computer Based Testing (ኮምፕዩተርን መሠረት ያደረገ ፈተና) ማለት ሲሆን ተፈታኙ በበይነ መረብ መፈተኑን እንዲሁም
- PPBT ማለት Paper Pencil Based Testing (ወረቀትን መሠረት ያደረገ ፈተና) ማለት ሲሆን ተፈታኙ በወረቀት መፈተኑን ለመግለጽ ነው፡፡
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