Sand Practical

Practical Write-up

Background:

There are two types of substances, they consist of pure substances and mixtures. A pure substance is one which it cannot be separated by physical means and consist of elements and compounds. Mixtures are not chemically bonded and therefore, have no defined ratio of and can consists of many compounds and elements and can usually be separated physically. Because of these properties it is to note that pure substance usually have defined physical properties such as melting/boiling point and density and mixtures can have varying physical properties as they are bonded in no specific ratio.

As mentioned before, due to mixtures being physically bonded it is possible to separate the compounds and elements consisted in a mixture through physical separation techniques. Separating mixtures can be accomplished in a variety of methods depending on the physical properties of the elements and compounds consisted in the mixture. Procedures to separate mixtures include but are not limited to: sieving, filtration, distillation, evaporation, magnetism and fractional sieving. Sieving involves taking advantage of difference in particle size, if one component of a mixture is significantly larger than the other then sieving can be used to separate the components as the smaller particles will go through the sieve whereas the larger ones will stay atop the sieve. Filtration works in a similar way as sieving but takes advantage of the fact that one component is a liquid and the other is a solid; and when you pour the substances onto a filter paper the liquid will pass through but the solids will not. Distillation is a technique which takes into account that there are two liquids in the substance. Distillation works because one of the liquids in the substance has a substantially higher boiling point and it works by boiling the whole substance. The component with the lower boiling point will boil much earlier and evaporate, the gas will then travel down a tube and form into liquid once again once it cools, this is all done while the other component remains as a liquid because of its much higher boiling point. Evaporation is a method in order to separate a liquid and a solid, the liquid having a relatively low boiling point. Evaporation works because after the liquid has evaporated only the solid from the mixture remains. Magnetism is a technique used in order to separate mixtures with a component of different magnetism values. If one component has a significantly higher magnetism value, then you are able to use a magnet to attract all of that substance while the other remains unmoved as its magnetism value is much lower.

Equipment:

• 1 x sample of wet beach sand
• 1 x Bunsen burner
• 2 x tripods
• 3 x filter papers
• 1 x pipe clay triangle
• 1 x evaporating basin
• 1 x heat mat
• 1 x stirrer
• 2 x funnels
• 3 x 250mL beakers
• 200mL of 2mol HCl
• 1 x scale, accurate to 0.01g

Method:

1. Obtain a sample of wet beach sand into one of the 250mL beakers
2. Place an empty beaker on the scales and tare the weight then place the beaker with sand onto the scale to find out the weight of the wet beach sand. (Record this)
3. Fold a filter paper and place it in the funnel
4. Place a beaker underneath the tripod and a funnel through the top of the tripod, you should be able to perform actions without holding the funnel
5. Slowly pour the wet beach sand mixture into the funnel that is held up by the tripod
6. When you have drained all the water from the beach sand weigh the filtrate
7. Pour the filtrate onto an evaporation basin  
8. Using a Bunsen burner, boil the filtrate until all the liquid evaporates.
9. Weigh the evaporation basin with the salt in it, then clean the basin to measure the basin without the salt.
10. Place the sand which is on the filter paper into an evaporating basin in order to evaporate any remaining liquid
11. Repeat step 9 but this time with the sand mixture in the evaporating basin
12. Place the remaining sand mixture into a beaker
13. Add the HCl into the beaker (about 30Ml at a time to avoid it reacting too strongly and overflowing)
14. Repeat step 12 until all the shells have reacted, you will know as when you add more HCl there is no reaction
15. Repeat step 4-9 with the mixture created by pouring HCl into the beaker.
16. The product should be sand only, weight this.
17. Using the measurements found throughout calculate the weight of the shells.

Results:

Total weight of mixture: 45.17g
Sand: 1.14g
Salt: 0.48g
Shells: 13.28g
Water: 30.27g

Calculations:

The percentage each component is as follow:

[pic 1][pic 2][pic 3][pic 4]

Discussion:

Due to the fact that there were no repeats of the practical due to time constraints there are not any particular patterns or trends to discuss. However, human errors were made throughout and can be, discussed. The first being in the step to filter the main mixture from liquid and solid using filtration. We were unable to scrape every bit of sand from the beaker of mixture onto the filter paper, the error being leftover sand on the beaker. An additional occurred in the next step where the mixture had finished being filtered and we were placing the sand on the filter paper into a beaker. Once again we were unable to scrape the entirety of the sand from the filter paper into the beaker, as a result there will be an errors in our calculations both for the sand and the shells. Last but not least, human error was a large factor in the calculations of our values. The weight of the shells is an assumption of the total mixture subtract each other component that we had separated. However, this assumption does not take into account the fact that there was leftover sand in both the filter paper and the beaker which makes both our sand and shells weight slightly off the real values it should be.