# A container holds 8.0kg of water at 25degC....

• MaryBarnes
In summary, to create 2.0 kg of steam from water, you need to add 7.12*106J of energy. This can be calculated using the formula Q total=mcwΔt+msLf, where Q total is the total energy, m is the mass of the material (in this case, water), c is the specific heat capacity, w is the change in temperature, and Lf is the latent heat of transformation. It is important to include all units in the calculation for accuracy.
MaryBarnes

## Homework Statement

how much energy must be added to the water to create 2.0 kg of steam?

## The Attempt at a Solution

I have no idea how I am supposed to figure the answer out. what formulas do I use?

What formula do you know that is related to heating and/or transforming material from one physical state to another? Those are the two processes which must occur here.

americanforest said:
What formula do you know that is related to heating and/or transforming material from one physical state to another? Those are the two processes which must occur here.
q=mLv

i attempted the answer:

Q total=mcwΔt+msLf
=8.0kg*4200j/kg*(100°C-25°C)+2.0kg*2.3*106
=7.12*106J

MaryBarnes said:
i attempted the answer:

Q total=mcwΔt+msLf
=8.0kg*4200j/kg*(100°C-25°C)+2.0kg*2.3*106
=7.12*106J
Yes.
If you want to make your working letter-perfect, include all units: 8.0kg*4200J/kg/°C*(100°C-25°C)+2.0kg*2.3*106J/kg.

haruspex said:
Yes.
If you want to make your working letter-perfect, include all units: 8.0kg*4200J/kg/°C*(100°C-25°C)+2.0kg*2.3*106J/kg.
awesome! thanks for the help!

## 1. What is the density of the water in the container?

The density of water at 25degC is 997 kg/m^3. Therefore, the density of 8.0kg of water in the container is 997 kg/m^3.

## 2. What is the volume of the water in the container?

The volume of water in the container can be calculated using the formula V = m/d, where V is the volume, m is the mass, and d is the density. In this case, the volume of water is 0.0080 m^3.

## 3. How much heat energy is required to raise the temperature of the water to 30degC?

The specific heat capacity of water is 4.186 J/g*degC. Therefore, the total heat energy required to raise the temperature of 8.0kg of water from 25degC to 30degC is 167.44 kJ.

## 4. What is the pressure inside the container?

The pressure inside the container can be calculated using the ideal gas law, PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature. In this case, the pressure inside the container is equal to the atmospheric pressure, which is approximately 101.3 kPa.

## 5. How long will it take for the water to reach 30degC?

The time it takes for the water to reach 30degC depends on various factors such as the heating method, the material of the container, and the surrounding temperature. However, assuming the water is heated with a constant power source, the time can be calculated using the formula t = mcΔT/Q, where t is the time, m is the mass, c is the specific heat capacity, ΔT is the change in temperature, and Q is the power. In this case, the time it takes for the water to reach 30degC will be approximately 8.2 minutes.

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