Chemistry

Microwave ovens heat food by creating microwave electromagnetic radiation that is absorbed by water molecules in the food. Any material that does not have water in it will not absorb the radiation and will not get hot. Metals reflect the microwaves from their surfaces and disrupt the operation of the oven. Some Australians heat water in microwave ovens to make tea. What is the minimum number of microwave photons with a wavelength of 3.28 mm that will have to be absorbed by a 112.00 gram sample of water to heat it from 25°C to 100°C? (It requires about 315 joules of energy to heat 1 gram of water 75°C)

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  1. How much heat do we need to raise T 112 g sample of water from 25 to 100? That's
    mass H2O x specific heat H2O x delta T = 112 x 4.184 x 75 = 35, 146 J.

    E 1 photon = hc/wavelenth
    E 1 photon = 6.626E-34*3E8^2/3.28E-3

    E/photon x #photons = 3,146 J
    And solve for # photons.

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