Steam vs. Boiling Water

Baoying Li 1B
Posts: 113
Joined: Sat Aug 17, 2019 12:18 am

Steam vs. Boiling Water

Can someone explain again why steam at 100 Celsius causes a worse burn than boiling water at 100 Celsius? I know Dr. Lavelle has talked about this during the lecture. I just want to make sure that if I get it right.

Angela Patel 2J
Posts: 110
Joined: Sat Aug 24, 2019 12:17 am

Re: Steam vs. Boiling Water

Basically, this is because steam has undergone a phase change from liquid to water vapor (vaporization). Vaporization requires a lot of energy. When steam touches your skin, it will release a lot of energy as it cools to form liquid water. Water, while at the same energy, does not have the same latent heat as steam since it is in a lower energy phase. Remember the graph that we saw in lecture!

Cole Woulbroun 1J
Posts: 56
Joined: Thu Jul 25, 2019 12:16 am

Re: Steam vs. Boiling Water

This concept has to do with the intermolecular forces between water molecules. Because of hydrogen bonding between water molecules, water at 100 C has to have a significant amount of energy placed into it in order to overcome these interactions and vaporize into steam. This large energy requirement allows different samples of water at 100 C to have different energy levels. Because of the difference in energy between steam at 100 C, which has enough energy overcome its hydrogen bonds, and water at 100 C, which does not have enough energy to overcome its hydrogen bonds, the burns that these two states of water cause are drastically different.

Bryan Chen 1H
Posts: 58
Joined: Mon Jun 17, 2019 7:24 am

Re: Steam vs. Boiling Water

there requires a large heat of vaporization (delta H) change to convert water molecules from the liquid to gas phase, so steam has much more "energy" in it

805307623
Posts: 99
Joined: Fri Aug 09, 2019 12:17 am

Re: Steam vs. Boiling Water

There's more energy in the steam, so to raise the temperature of one gram of water to 100'C requires less energy than it takes to convert that same gram of water to steam. The energy in the steam is greater than the energy in the same weight of water at the boiling point, and this heat is released when the steam condenses to water and cools to the skin's temperature.

Ayushi2011
Posts: 101
Joined: Wed Feb 27, 2019 12:17 am

Re: Steam vs. Boiling Water

To put it in simpler terms, changing the state of a substance releases a lot more energy than the substance remaining in the same state. Water at 100C releases less heat than steam because the change in state from water to steam (vaporisation), releases more energy.

905373636
Posts: 62
Joined: Thu Aug 01, 2019 12:15 am

Re: Steam vs. Boiling Water

Angela Patel 2J wrote:Basically, this is because steam has undergone a phase change from liquid to water vapor (vaporization). Vaporization requires a lot of energy. When steam touches your skin, it will release a lot of energy as it cools to form liquid water. Water, while at the same energy, does not have the same latent heat as steam since it is in a lower energy phase. Remember the graph that we saw in lecture!

Despite this energy difference, though, the liquid and gas are at the same temperature? How does that work?

Jasmine Kim 1L
Posts: 71
Joined: Fri Aug 02, 2019 12:16 am

Re: Steam vs. Boiling Water

905373636 wrote:Despite this energy difference, though, the liquid and gas are at the same temperature? How does that work?

The liquid and gas aren't at the same temperature. The horizontal lines on the graph represent phase changes. They are flat because the heat is being used to break bonds, which absorbs the energy and keeps the temperature from rising. The steam that is rising has already broken all of its bonds and therefore, the temperature is increasing again and it is hotter than it was as liquid water.

Daria MacAuslan 1H
Posts: 50
Joined: Sat Aug 17, 2019 12:16 am

Re: Steam vs. Boiling Water

Steam at 100 degrees celcius is clearly extremely hot, and when it touches skin, there is a huge difference in temperatures. The steam then undergoes a phase change extremely rapidly, going from a gas form to a liquid water form. This releases a lot of energy and thus ends up creating a much more intense burn.

Mariah
Posts: 104
Joined: Fri Aug 02, 2019 12:16 am

Re: Steam vs. Boiling Water

Angela Patel 2J wrote:Basically, this is because steam has undergone a phase change from liquid to water vapor (vaporization). Vaporization requires a lot of energy. When steam touches your skin, it will release a lot of energy as it cools to form liquid water. Water, while at the same energy, does not have the same latent heat as steam since it is in a lower energy phase. Remember the graph that we saw in lecture!

So is it basically all related to the phase and that steam is a vapor and water is a liquid? What is the order of phases and their energies?

Angela Patel 2J
Posts: 110
Joined: Sat Aug 24, 2019 12:17 am

Re: Steam vs. Boiling Water

Mariah wrote:
Angela Patel 2J wrote:Basically, this is because steam has undergone a phase change from liquid to water vapor (vaporization). Vaporization requires a lot of energy. When steam touches your skin, it will release a lot of energy as it cools to form liquid water. Water, while at the same energy, does not have the same latent heat as steam since it is in a lower energy phase. Remember the graph that we saw in lecture!

So is it basically all related to the phase and that steam is a vapor and water is a liquid? What is the order of phases and their energies?

Gas has a higher internal energy than liquid, and liquid has a higher internal energy than a solid. You could think about the intermolecular forces to understand why.