Physics 9702 · AS & A Level · Specific heat capacity and specific latent heat

Specific heat capacity and specific latent heat — practice question

A microwave cooker makes use of electromagnetic waves with a frequency of $2450\,\text{MHz}$. These microwaves heat the food by making water molecules in the food oscillate with a large amplitude at the microwaves’ frequency.
(a)[1]

State the term used for this phenomenon.

(b)[3]

The microwave cooker has an effective power of $750\,\text{W}$. A mass of $280\,\text{g}$ of water is heated from $25\,^\circ\text{C}$ to $98\,^\circ\text{C}$ in $2.0\,\text{minutes}$. Calculate a value for the specific heat capacity of the water.

(c)[1]

The specific heat capacity value calculated from the data in (b) is larger than the accepted value. A student explains this difference by saying ‘heat lost to the surroundings’. Suggest, in more detail than that given by the student, a possible reason for the difference.

Worked solution & mark scheme

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