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Question hi i really need help in writing out my science experiment report i was wondering if you could help me.
Separating a Mixture
Introduction
A mixture is an impure substance, which means it had a variable composition, it can be separated by physical methods of separation such as filtering. Filtration and evaporation are two physical methods of separation that will be used in this experiment. Filtration removes insoluble components of a mixture from soluble ones, while evaporation separates a mixture by vaporization of the low boiling component to leave the high boiling component as a residue. Gravimetric analysis, which involves weighing substances to find the percentage composition of a mixture, will be used.
Aim: To carry out a gravimetric analysis to estimate the percentage composition of sand, salt and water in the mixture given.
Equipment:
150mL beaker
mixture of sand salt and water
filter paper
funnel
Bunsen burner
250mL conical flask
heat proof mat
gauze mat
electronic balance
matches
tripod
stirring rod
oven
spoon
watch glass
evaporating dish
Safety:
Wear safety goggles to avoid eye irritation in case of the hot water splashing, or sand coming in contact with eyes.
Method:
1) Weigh the entire mixture with beaker using the electronic balance
2) Record your results
3) Set up the apparatus as shown in Diagram 1
4) Pour mixture through filter paper into conical flask
5) Use spoon to remove all of the sand from beaker into filter
6) Remove filter paper carefully from funnel after the whole mixture has been satisfactorily filtered
7) Place the filter paper with the sand on the watch glass
8) Place watch glass in oven and leave in there till all the water has evaporated
9) Weigh beaker using electronic balance
10) Record your results
11) Set up apparatus as shown in Diagram 2
12) Evaporate the water until the salt starts crusting the surface of the water stir the mixture occasionally using the stirring rod
13) Place the evaporating dish into the oven to evaporate the rest of the water
14) Minus the mass of the beaker from the mass of the entire mixture( the one you weighed in step 1)
15) Record your results
16) Weigh the sand using the electronic balance
17) Record your results
18) Weigh the entire evaporating dish with the dried salt in it
19) Record your results
20) Wash off the dried salt from evaporating dish and dry it
21) Weigh dried evaporating dish
22) Record your results
23) Minus the weight of the beaker from the weight of the total mixture with beaker(referring to step 1) to find the mass of the entire mixture
24) Record your results
25) Minus evaporating dish from evaporating dish with salt to find mass of salt
26) Record your results
27) Minus the combined mass of the salt and sand from the mass of the entire mixture to find mass of water
28) Record your results
29) Use gravimetric analysis to find the percentage of composition of the mixture
30) Record your results
31) Repeat experiment 10 times
Diagrams
Results
Substance Mass(g) Composition (%)
Sand 22.67 27.50
Salt 8.30 10.07
Water 51.47 62.43
Total 82.44 100
Discussion
Validity: The design of the experiment was to find the mass of each of the componenets in the mixture to eventually find out the percentage composition using Gravimetric analysis. This experiment did help to find out the mass of each; the water, sand and salt in the mixture. However, there was one problem faced by us. The problem was that there was salt in the sand after we had taken it out of the oven, this resulted in the mass of the sand being more than it should be and the mass of the salt less than it should be. The salt appeared in the sand after we took it out of the oven, because when we filtered the mixture not all of the salt water had been removed from the sand, some of it stayed with the residue, as a result we got some salt in the sand residue.
Variables:
Controlled variable: method used to calculate percentage(gravimetric analysis), entire mixture, electronic balance,
Accuracy: The accuracy of the experiment was good as the electronic balance used measured the quantitative results up to two decimal places and was digital which meant that there was no parallax error when the mass was measured. It however could have been improved if the electronic balance measured up to three or four decimal places.
Reliability: The reliability of the experiment is overall not very reliable as we only did it once, however, if the whole class is taken into consideration well than the experiment is reliable because it has been tested around 10 times, by the whole class and similar results have been achieved in every test.
Conclusion
The percentage composition of sand was 27.50%, the percentage composition of salt was 10.07% and the percentage composition of water was 62.43%.
Bibliography
Schwengel, K. (Unknown). How to Write an Introduction for a Lab Report. Retrieved February 7, 2008, from eHow: http://www.ehow.com/how_2066040_write-introduction-lab-report.html
Science Exercise book( notes and worksheets)
Miscellaneous notes:
◆ the actual amount placed in each mixture was sand: 20g, alt 10g, water 60g.
Answer Hi,
It is reasonably well written.
I liked the part where salt was also found in the sand!
Very realistic.
My suggestions.
1 )
To improve our results (to gain accuracy), one can always improvise and do things that are "not done by the class as a whole"! :)
What is to prevent you with washing the sand after isolation by filtering, till all (99%) of salt water adhering to the sand is diluted away!?
The oven is anyway going to "take away" all the added water!
But look at the improvement that will get you. Your estimate of sand will be almost 100% accurate.
Other parts of the experiment will not be degraded but atleast 1 part (sand measurement) will be almost 100% accurate.
2) - salt & water estimates can be further enhanced if say you add 1 or two litres of distilled water before filtration of sand. (you add 1 kilo of water to your starting mixture, thus diluting the salty water. This way, after filtration, less salt adheres to the sand.
- Then wash the sand in plenty of water and bake. giving accurate sand result.
- Then boil away the water and bake the remnant, and note weight of water lost.
- since the filtrate had almost all the salt (no doubt much diluted), your salt estimate will be most accurate.
- since water lost by adhesion is a very small percentage of by weight of water after addition of 1 litre,
the weight of water lost - 1 kilo will yield very accurate figure for water in the starting mixture!
remember:- The trick was to add a known weight of solvent to carry over all the solute into the filtered solution, then remove all the solvent! you end up extracting almost all the solute.
weight of original amount of water in kilos = (wieght of filtrate) - (measured weight of salt from oven) - 1 kilo of added water weight.
Lastly adding bullets to the introduction clearly enumerating various methods (as you have done for the equipment), will greately enhance the appeal of the report.
Please do rate my answer if you find it interesting.
