2. Water at the Antarctica usually exits as ice, making it very difficult to use the water or conduct experiment requiring the water to be in liquid state. A coffee addicted physicist stationed at a research base requires about 0.8 kg of ice for his coffee on the hour.
a. How much heat is required to convert 0.8 kg of ice at —35 °C into steam at 100°C?

662480 J

Explanation:

The heat required to convert 0.8Kg of ice at -35°c to steam at 100°c is the sum of the heat required to raise the temperature of the ice from -35°c to 0°C, the latent heat of fusion of ice and the heat required to raise the temperature of the ice from 0°c to 100°c.

Latent heat of fusion for ice= 3.36× 10^5 J Kg-1

Specific heat capacity of ice= 2060 J kg−1K−1

Specific heat capacity of water= 4200 JKg-1K-1

Heat required to raise the temperature of the ice to fusion point

H= 0.8 × 2060 × [0-(-35)]

H= 57680 J

Latent heat of fusion of ice;

H= mL

H= 0.8 ×3.36× 10^5

H= 2.688×10^5 J

Heat required to raise the temperature of the water to 100°C

Since mass is conserved, the mass of ice that has melted has been turned into an equivalent mass of water.

Therefore mass of water formed= 0.8Kg

H= 0.8× 4200 × 100

H= 336000J

Therefore total heat required;

H= 57680 + 2.688×10^5 + 336000

H= 662480 J

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.