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

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 (°C)

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Controlled variables:

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Materials

• 200g of Woolworth Iodated Table Salt
• 3L of science lab tap water
• 2 × 500mL wash bottle
• 6 × 500mL beakers
• 1 × 500mL graduated cylinder
• 1 × stop watch
• 1 × -50 – 150°C digital thermometer
• 1 × beakers tongs
• 1 × permanent pen
• 1 × Bunsen burner
• 1 × tripod
• 1 × stirring rod
• 1 × 10g/10mL mini sampler spoon

Method

1. Two tables were drawn up to record qualitative and quantitative data

Quantitative data

Qualitative data

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

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3

=   average boiling point temperature (°C)

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Bibliography

1. How Does Salt Affect the Boiling Point of Water. . 27 Dec 2006. 07 Feb 2009.