How much energy is needed to heat enough water to make a cup of tea (250 ml), if the water is initially at 20.0°C and you want to increase the temperature to 85.0°C? (1.00 mL of water has a mass of 1.00 g.) As the tea in the previous question steeps, it cools from 85.0°C to 75.0°C. How much energy is lost by the tea as it steeps?

Heat Energy needed (Q) = 68250 J

Energy lost (Q') = 10500 J

Explanation:

Applying,

Q = cm(t₂-t₁) Equation 1

Where Q = heat  energy needed, c = specific heat capacity of water, m = mass of water, t₁ = initial temperature, t₂ = final temperature.

From the question,

Given: m = 250 g = 0.25 kg, t₁ = 20.0°C, t₂ = 85.0°C

Constant: c = 4200 J/kg°C

Substitute these values into equation 1

Q = 0.25(4200)(85-20)

Q = 68250 J.

Similarly, heat lost

Q' = cm(t₁-t₂) Equation 2

Where Q = heat lost

Given: t₁ = 85°C, t₂ = 75°C

Substitute into equation 2

Q' = 4200(0.25)(85-75)

Q' = 10500 J

on passing the small ampere of electric current through the tube made of ar and hg of cfl generates uv rays which excites the fluorescent and thus emits the high radiation by consumption of just 5- 12 w in comparison to incandescent light which requires more power such as around 40 - 55 w to lighten.

moreover the life span of fluorescent or cfl is around 8000 h whereas the life span of incandescent is around 1200 h

hence, the building installed with incandescent lights bears more electricity bill.