6.2.11
The idea that I have chosen to conduct is the concentration of salt and how it will affect waters boiling point. Today I have done some primary research to learn a bit about salt and water.
Research on my chosen idea:
• Dissolving salt in a liquid, like water, when dissolving one substance which is known as the solute, in this case the salt, into another solvent which is the water, it will raise the boiling point of more than 100℃.
• The degree of the water changing depends on how much solute you dissolve in the liquid. The temperature of the water does not change relying on the type of solute.
• If the salt is dissolved in the liquid (water), the number of water molecules weaken and are overtaken by the particles of the salt. The vapour pressure of the solvent lowers which means that there needs to be a higher temperature to boil the water with the salt solution.
• When carrying out this experiment keep the heat source constant.
• As soon as any of the salt dissolves in water, the boiling point rises by about 1½℃ for every 58 grams you put in of salt.
• Not only salt, but any non-changeable substance will raise the boiling point of water.
• Small amounts of salt added will be completely dissolved before the bubbling begins to occur. The salt water will need to be exposed to more heat than the pure water to boil. The salt water will boil slower than the pure water.
• Salt, or other solutes, such as sugar can easily dissolve in liquids especially water. But, when taking out the solute which is salt out of the water and putting it into the air it needs a lot of energy.
• Now the total pressure in the liquid and the air at the boundary are the same- otherwise one would push the other into a smaller space. Part of the pressure in the liquid comes from the solutes, not the water. So the pressure due to the water alone is reduced compared to that of pure water at the same temperature. The vapor pressure, that is, the pressure of water vapor that would stay in equality with the liquid, is reduced by the same amount because of the solutes.
• Water boils when the vapor pressure of the water gets to be as big as the pressure of the atmosphere. At that point, vapor bubbles in the water can grow. You have to heat the liquid with solutes up more to get the vapor pressure in it to equal the atmospheric pressure, so it has a higher boiling point.
• A very similar argument explains why solutes also lower the freezing point. Since the solutes are almost completely excluded from the solid (like from the gas) they stabilize the liquid. A search of this site will turn up some answers about freezing salt water.
- Today I also emailed the commonwealth Scientific and industrial research organisation (CSIRO) and I had asked them for some research and links for my chosen topic. They said that they will email me in approximately two business days.
