1) Two glasses contain 500 mL of water each. The water in glass A has a temperat

Question

1) Two glasses contain 500 mL of water each. The water in glass A has a temperature of 66oC, the water in glass B has a temperature of 94oC. The two waters are mixed together in a larger glass. Is the final temperature of the mixture (i) greater than, (ii) less than, or (iii) the same as the average temperature of 80oC of the two glasses? Explain your reasoning.

2)Two glasses contain 500 mL of liquid. The liquid in glass A has a temperature of 66oC, the (different) liquid in glass B has a temperature of 94oC. The liquid in glass A has a larger specific heat than the liquid in glass B. The two liquids are mixed together in a larger glass.

Is the final temperature of the mixture:

a. greater than

b. less than

c. the same as

the average temperature of 80oC of the two glasses? Explain your reasoning

3) Suppose we heat sample A, which is 150 g of ice at -10oC, and sample B, which is 150 g of ice at 0oC, in the same microwave oven until both samples are water at 30oC.

Will the time taken to heat sample A be:

a. Longer than

b. Shorter than

c. Equal to

The time taken to heat sample B? Explain your reasoning.

Explanation / Answer

!)

Two glasses A and B contain 500 mL of water each. Temperatures are, for A 66oC and 94oC.

Average of these two different tempeartures is 80oC.

When the contents of these two glasses A and B are mixed ,

heat lost = heat gained

d x 500 x s x ( T - 66) = d x 500 x s x ( 94 - T)

d = density of water

s = specific heat of water

final temperature = 80 oC = average temperature

This is because both liquids have same specific heat and same mass.

2)

Now liquids are different.

sA > sB

dA x 500 x sA x ( T - 66) = dB x 500 x sB x ( 94 - T)

If we assume that densities are equal.

Final temperature T = ( 94sB + 66sA ) / ( sA + sB )

this is less than 80oC.

since T = ( 94sB + 66sA ) / ( sA + sB ) = ( 80sB + 80sA + 14sB - 14sA) / ( sA + sB ) =

80 + (negative number)

3)

If the rate of flow of heat to the samples is the same for A and B,

A will take a longer time to reach 30oC, since A has to absorb more heat.( for incereasing it's temperature from -10oC to 0oC )

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.