Quantity of Heat | Jamb(UTME)

Quantity of Heat

1. Heat is a form of energy that flows from a hotter body to a cooler body.
2. The quantity of heat is the amount of thermal energy transferred between objects due to a temperature difference.
3. It is measured in joules (J) in the SI system.
4. Heat transfer can occur through conduction, convection, or radiation.
5. The formula to calculate the quantity of heat is:
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   $Q = mc\Delta T$ where:
   • $Q$ = Heat energy,
   • $m$ = Mass,
   • $c$ = Specific heat capacity,
   • $\Delta T$ = Change in temperature.
6. A higher temperature difference results in a greater transfer of heat.
7. Heat can be absorbed or released during phase changes, like melting or boiling.
8. The amount of heat transferred depends on the substance's mass and specific heat capacity.
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Heat as a Form of Energy

9. Heat is a type of kinetic energy, related to the motion of particles within a substance.
10. Heat energy can change the temperature of a substance or cause a change of state.
11. Heat is conserved in an isolated system, following the law of conservation of energy.
12. Heat energy can be converted into other forms of energy, such as mechanical energy in engines.
13. It is different from temperature, which measures the average kinetic energy of particles.
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Heat Capacity of Solids

14. Heat capacity is the amount of heat energy needed to raise the temperature of an object by $1C$ or $1K$.
15. The formula for heat capacity is:
    
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    $C = \frac{Q}{\Delta T}$ where $C$ = Heat capacity, $Q$ = Heat energy, $\Delta T$ = Temperature change.
16. Heat capacity depends on the mass and type of material.
17. Solids like metals have lower heat capacities compared to materials like wood.
18. Metals, with high thermal conductivity, heat up quickly and have smaller heat capacities.
19. The larger the solid object, the higher its heat capacity.
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Heat Capacity of Liquids

20. Liquids generally have higher heat capacities than solids.
21. Water, with a high heat capacity, can absorb and store large amounts of heat.
22. The heat capacity of a liquid depends on its mass and type.
23. Liquids with higher heat capacities are useful in cooling systems, like water in car radiators.
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Specific Heat Capacity of Solids

24. Specific heat capacity is the amount of heat energy required to raise $1kg$ of a substance by $1C$ or $1K$.
25. The formula for specific heat capacity is:
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    $c = \frac{Q}{m\Delta T}$ where $c$ = Specific heat capacity, $Q$ = Heat energy, $m$ = Mass, $\Delta T$ = Temperature change.
26. Different materials have different specific heat capacities.
27. Metals like aluminum and copper have low specific heat capacities, meaning they heat up quickly.
28. Non-metals like wood and plastic have higher specific heat capacities.
29. The specific heat capacity of solids is crucial in designing cookware, buildings, and machinery.
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Specific Heat Capacity of Liquids

30. Water has a specific heat capacity of $4200J/kg·K$, one of the highest among common substances.
31. Liquids with higher specific heat capacities are effective in regulating temperature changes.
32. Specific heat capacity determines how quickly a liquid heats up or cools down.
33. Liquids like alcohol have lower specific heat capacities compared to water.
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Determination of Heat Capacity

34. Heat capacity can be determined by supplying a known amount of heat to a substance and measuring the temperature change.
35. Use the formula $C = \frac{Q}{\Delta T}$, where $Q$ is the heat supplied and $\Delta T$ is the temperature rise.
36. Electrical methods involve passing a known current through a heating element and measuring the heat transferred.
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Determination of Specific Heat Capacity

37. Method 1: Electrical Method
    • Heat a known mass of a substance using an electric heater.
    • Measure the energy supplied $Q = IVt$, where $I$ = current, $V$ = voltage, $t$ = time.
    • Measure the temperature rise and calculate specific heat capacity using $c = \frac{Q}{m\Delta T}$.
38. Method 2: Method of Mixtures
    • Mix a hot object with a cooler liquid of known mass and specific heat capacity.
    • Measure the final temperature and use the principle of conservation of energy to calculate $c$.
39. Method 3: Calorimetry
    • Place a solid or liquid in a calorimeter and measure the temperature changes.
    • Use the heat gained or lost by water in the calorimeter to calculate specific heat capacity.
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Applications of Specific Heat Capacity

40. Water's high specific heat capacity makes it ideal for regulating temperatures in oceans and climates.
41. Cooking utensils are made of metals with low specific heat capacities to heat quickly.
42. Specific heat capacity is considered in building materials to ensure efficient thermal insulation.
43. Coolants like water and antifreeze use their high specific heat capacities to absorb engine heat.
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Practical Observations

44. A cup of hot water cools down slower than a cup of tea due to water's high specific heat capacity.
45. Metals feel colder than wood at room temperature because metals have lower heat capacities and conduct heat away faster.
46. Deserts experience extreme temperatures because sand has a low specific heat capacity.
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Real-Life Importance

47. Specific heat capacity explains why water bodies moderate coastal climates.
48. Engineers use heat capacity data in designing heat exchangers and thermal systems.
49. Specific heat capacity data is essential in understanding energy storage in materials.
50. The study of heat capacities contributes to advancements in energy conservation and thermal management.
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