Salt water steam pressure vs fresh water steam pressure

In summary, my son's 5th grade science project was to build a steam powered boat using candles. He changed the experiment to see if salt water would push the boat better than fresh water. His results showed that on average the salt water powered boat traveled farther than the fresh water in the same given time. His observations were that the fresh water started pushing steam out sooner than the salt water, however the salt water powered steam was more consistent than the fresh water. Can you point me in a direction that supports these results. Do they sound valid or do we have a case of experimental error. I helped him and made sure that we kept all processes the same so we weren't influencing a result. Is the added solution with a higher boiling point releasing
  • #1
Makai
3
0

Homework Statement



My son picked a science experiment for his 5th grade project. It was supposed to be on evaporation. Basically a steam powered boat with candles heating up a cigar tube with a hole for the steam to escape and push the boat. However he got ambitious and changed the experiment with his teacher to see what would work better fresh water vs. a salt water solution. My son theorized that fresh water would push the boat better than salt water after researching about boiling points and elevated boiling points due to the addition of salt water. The conditions were the same as far as time frame, amount of water, and temp of water added to the tube. However his results show that on average the salt water powered boat traveled farther than the fresh water in the same given time. His observations were that the fresh water started pushing steam out sooner than the salt water, however the salt water powered steam was more consistent than the fresh water. Can you point me in a direction that supports these results. Do they sound valid or do we have a case of experimental error. I helped him and made sure that we kept all processes the same so we weren't influencing a result. Is the added solution with a higher boiling point releasing steam at a higher pressure due to more molecular bonds being broken?

Homework Equations





The Attempt at a Solution


He is looking into vapor pressure and is trying to come to a conclusion. Vapor pressure is lowered with salt added to the water so it takes more heat to release vapor so would this create more pressure thus pushing the boat faster.
Thanks
 
Physics news on Phys.org
  • #2
For the salty water escaping vapor has a higher temperature - I would try to think how it can change the propulsion effectiveness. But I am just thinking aloud, I don't have any solid idea about what is happening.
 
  • #3
It's been a while for me but I am thinking that because we have a higher boiling point the steam would be at a higher temperature thus increasing the pressure in the tube. Therefore we should have an increase of kinetic energy. I'm just trying to make sure we have a valid conclusion.
 
  • #4
Steam will be hotter, but the pressure in the tube will be identical in both cases - that's because boiling means vapor pressure is equal to the surrounding pressure (which doesn't change).
 
  • #5
Yes but if you have a higher temp you should be releasing more energy you couldn't have the same result with water vs a solution. Somehow there should be a change more energy in = more energy out.
 
  • #6
Hotter steam contains more energy at the same pressure.

At least per mass unit.

I think I will move this thread to the engineering section.
 

1. What is the difference between salt water steam pressure and fresh water steam pressure?

Salt water steam pressure refers to the pressure of steam generated from salt water, while fresh water steam pressure refers to the pressure of steam generated from fresh water. The main difference between the two is the salt content, which affects the boiling point and therefore the pressure required to produce steam.

2. How does the salt content in water affect steam pressure?

The higher the salt content in water, the higher the boiling point. This means that salt water requires a higher temperature and pressure to turn into steam compared to fresh water. As a result, the steam pressure produced from salt water will be higher than that of fresh water.

3. Is it possible to have higher steam pressure with salt water compared to fresh water?

Yes, due to the higher boiling point of salt water, it is possible to achieve a higher steam pressure with salt water compared to fresh water. This is why some industries, such as power plants, use salt water to produce higher pressure steam for more efficient and powerful operations.

4. Why is it important to consider the type of water when measuring steam pressure?

The type of water used can greatly affect the steam pressure and therefore the efficiency of steam-based systems. Using the incorrect type of water can result in lower pressure, which can impact the performance of equipment and processes that rely on steam, such as turbines and boilers.

5. How do scientists measure and compare salt water steam pressure and fresh water steam pressure?

Scientists typically use a pressure gauge or a manometer to measure steam pressure. These instruments can accurately measure the difference in pressure between salt water and fresh water, allowing for a comparison to be made. Other factors, such as temperature and salinity, may also be taken into account when measuring and comparing steam pressure from different types of water.

Similar threads

  • Thermodynamics
Replies
8
Views
1K
Replies
25
Views
2K
Replies
13
Views
1K
  • Engineering and Comp Sci Homework Help
Replies
1
Views
2K
  • Classical Physics
Replies
3
Views
712
  • Engineering and Comp Sci Homework Help
Replies
16
Views
2K
Replies
7
Views
4K
Replies
8
Views
951
  • Mechanical Engineering
Replies
16
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
5
Views
3K
Back
Top