Investigate the effect of one factor on the boiling temperature of a liquid Essay

Salt (NaCl) is a substance with a low vapour pressure. In comparison to any type of liquid, salt still has a lower vapour pressure. If salt was to be dissolved in water (H2O), in this case for the experiment, then consequently the salt will cause the overall vapour pressure of the solution to decrease and have a lower vapour pressure. Lowering a solution’s vapour pressure means that the solution will have a higher molecule vaporising point then pure water (without added salt). In other words, the boiling point of the solution will increase and therefore have a higher boiling point temperature. A term used to describe this outcome is also known as boiling-point elevation. [1] In this experiment the affect of table salt on the boiling point of tap water will be measured. Pure tap water without table salt added will be the control of this experiment and all results will be compared to the results of the pure tap water. The temperature of the water will be measured in degrees Celsius (à ¯Ã‚ ¿Ã‚ ½C) and the amount of table salt added will be measured in grams (g). This experiment will be carried out at Standard Lab Conditions (SLC); Research Question: How does table salt affect the boiling point of water? Hypothesis: It is hypothesised that adding table salt will cause the water to boil at a higher temperature. Variables: Independent variables: The amount of table salt added to water. (g) * 0 grams (control) * 10 grams * 20 grams * 30 grams * 40 grams * 50 grams Dependent variables: The temperature of water when it boils (à ¯Ã‚ ¿Ã‚ ½C) Controlled variables: Controlled variables How it will be controlled The conditions of the surrounding area (temperature, wind, humidity etc) of where the experiment is carried out The experiment will be carried out on one day only and at standard lab conditions Avoid salt residues left on the thermometer when testing water temperature Distilled water will be used to clean the thermometer before every testing of water The type of water used for the experiment Tap water for the science lab will be used for this experiment The point at which the water temperature will be recorded The temperature of the water will be recorded when the whole surface of the water is boiling and bubbling The length of time the thermometer is left in the beaker of water The thermometer will be left for 30 seconds in the beaker, to show clear results of the water temperature The depth at which the thermometer is left in the beaker The end tip of the beaker will be placed right at the centre bottom of the beaker The Bunsen burner flame that will heat the beaker The heat of the blue flame will boil the water in the beaker The length of time the Bunsen burner is left undisturbed on blue flame to reach its optimum temperature When the Bunsen burner safe flame is changed to blue flame, the Bunsen burner will be left on the bench undisturbed for 2 minutes The repetition and speed of stirring the solution When the beaker is placed onto the tripod with the blue flame on, immediately 5 slow circle rotations of the stirring rod will be performed to dissolve the salt into the water The amount of water used for this experiment For this experiment, 500 millimetres of water will be measured in the beakers. When measuring the water level, the observer must get down to eye level to avoid parallax error and misreading of the water level Avoiding contaminations to the equipment used in this experiment Before using equipments, distilled water will be used to thoroughly clean all equipments to avoid contamination and residues The brand and type of table salt used for this experiment Woolworths Iodated Table Salt will be used for this experiment The accuracy of measuring small amount of salt The sampler spoon will be filled with salt right to the top, (touching the edges but not overflowing) with salt. 2. A wash bottle was used to thoroughly clean all equipments of this experiment. Including: beakers, graduated cylinder; thermometer, stirring rod 3. With a permanent marker pen, each beaker was labelled (near the top mouth of the beaker): Control; 10g; 20g; 30g; 40g; 50g; respectively, in relation to the amount of salt that will be added to the water 4. The graduated cylinder was used to measure 500mL of tap water, and the tap water was then placed into a beaker. This was repeated until all six beakers were filled with 500mL of tap water 5. The sampler spoon was used to weigh the amount of table salt that each beaker of water needed according to the labels of the beakers Eg; If the beaker is labelled 30g, then 30g of salt must be added to the beaker. Which means salt will have to be scooped three times with the spoon 6. The Bunsen burner was set up and the safe flame was left on. The tripod was placed directly above the flame 7. When the Bunsen burner was changed to the blue flame, the stopwatch was used to record 2 minutes of the flame left undisturbed 8. The beaker that read Control was immediately placed onto the tripod after two minutes was up 9. The stirring rod was instantly retrieved and 5 slow circle rotations were performed to dissolve the salt into the water 10. The beaker was left stable on the tripod. Whilst waiting for the water to boil, changes to the solution was carefully observed. Observations were recorded as qualitative data. When the whole surface of the water boiled, the tip of the thermometer was immediately placed at the centre of the beaker for 30 seconds. The degree of the water was then recorded. 11. In avoiding dangers, the blue flame was changed to the safe 12. The beaker tongs was used to remove the beaker from the tripod and the beaker was then placed away from the experiment area 13. The wash bottle was used to clean residues off the thermometer. 14. Steps 7-12 was then repeated for the rest of the beakers labelled; 10g; 20g; 30g; 40g; 50g 15. In obtaining more accurate results, the whole experiment was carried out another three times and the average was then calculated: Test 1 result + Test 2 result + Test 3 result Bibliography 1. How Does Salt Affect the Boiling Point of Water. David Bradley. 27 Dec 2006. 07 Feb 2009. http://www.sciencebase.com/science-blog/how-does-salt-affect-the-boiling-point-of-water.html