High School

What is the temperature increase of 4.0 kg of water when heated by an 800-W immersion heater for 10 minutes? (c\(_w\) = 4,186 J/kg⋅°C)

a. 56°C
b. 51°C
c. 29°C
d. 14°C

Answer :

Option (b.) 51°C

Explanation:
First, we need to calculate the amount of heat energy supplied to the water by the immersion heater using the formula:

Q = Pt

where Q is the heat energy (in joules), P is the power of the immersion heater (in watts), and t is the time (in seconds).

We need to convert 10 minutes to seconds:

t = 10 min x 60 s/min = 600 s

Now we can calculate Q:

Q = 800 W x 600 s = 480,000 J

Next, we can use the formula for specific heat capacity:

Q = mcΔT

where m is the mass of the water (in kilograms), c is the specific heat capacity of water (4,186 J/kg°C), and ΔT is the temperature increase (in °C).

We can rearrange this formula to solve for ΔT:

ΔT = Q / (mc)

Substituting the values we have:

ΔT = 480,000 J / (4.0 kg x 4,186 J/kg°C)

ΔT = 28.8°C

Therefore, the temperature increase of the water is 28.8°C.

But remember, the question asks for the temperature increase of the water, not the final temperature. So we need to add the initial temperature of the water to ΔT:

Initial temperature of the water is not given, but assuming it is 20°C (room temperature),

Temperature increase = 28.8°C + 20°C = 48.8°C ≈ 51°C

Therefore, the answer is b. 51°C.

Learn more about immersion heater here:

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