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3 years ago

1. How much heat is necessary to vaporize 500 g of water at its boiling point?

1 answer:

3 0

1. When water converts to vapor phase from liquid phase, there is no any temperature change. In other words, when a substance changes its phase, the temperature remains constant.

So we can use the formula

Q = mL

Where Q is the heat (J), m is the mass (g) and L is the latent heat (J/g).

M = 500 g

L = Latent heat of vaporization = 2230 J/g

Hence, Q = 500 g x 2230 J/g = 1115000 J = 1115 kJ

Hence, 1115 kJ of heat is needed to vaporize 500 g of water at its boiling point.

2. Let’s assume that water is at its freezing point (0 ⁰C). Then there is only phase conversion and no any temperature change. Again we can use the formula,

 Q = mL

Here, Q is the heat that given off (J), m is the mass (g) and L is the latent heat of fusion (J/g).

Q = 5100 J

L = 334 J/g

Hence, 5100 J = m x 334 J/g

m = 5100 J / 334 J/g

m = 15.269 g

Hence, the mass of water is 15.269 g.

3. When condensing vapor into its liquid again it is only a phase conversion and temperature remains as constant (100 ⁰C).

Hence, we can use the formula,

 Q = mL

Here, Q is the heat that given off (J), m is the mass of vapor (g) and L is the Latent heat of vaporization (J/g).

Q = 57.500 J

L = 2230 J/g

By applying the equation,

57.500 J = m x 2,230 J/g

m =0.0258 g

Hence, the mass of steam is 0.0258 g.

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You apply the same amount of heat to five grams of water and five grams of aluminum. The temperature of the aluminum increases m

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Motion requires energy: The more energy matter has the higher temperature it will also have. Typicall this energy is supplied by heat. Heat loss or gain by matter is equivalent energy loss or gain.

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Example 1: How much energy does it take to raise the temperature of 50 g of copper by 10 0C?

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