This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.
The aims of these experiments are to practice the skills of practical interactions, handling liquids, measuring temperature, observing some reactions between liquids and solids, and some reactions.
Interactions are the main point of these experiments; and to observe different behaviors between different liquids and liquids or liquids and solids.
Water plays an important part in these experiments; many materials are soluble in water. RS?C (2009) gives the reasons for why materials can dissolve in it. There are some Hydrogen ions and Hydroxide ions in water, both of them can interact with other materials and they can dissolve in water.
According to 'van der Waals Forces and Equation' (2009), Van der Waals force is a kind of attraction between molecules; it is much weaker than chemical bonds. Van der Waals force can also known as intermolecular force. Molecules can be transformed into liquid from gas, and from liquid to solid. This shows that a interaction force is being between molecules. This force is Van der Waals force.
According to Hydrogen Bonds (2009) , if the Hydrogen which covalent bind with large electro negativity of atoms (such as fluorine, oxygen and nitrogen) are close to a great negative electric atom, Hydrogen will be a medium to produce a kind of bond, this kind of bonding is called Hydrogen bond.
Baidubaike(2009b) states Hydrogen bonds offer the main binding force between water molecules. However, the solutes that can provide the capability Hydrogen bonds or acceptance of Hydrogen ion are those structural similar with water. These explain why different liquids can mutual dissolution, as long as they are similar.
These experiments include seven tests which are about mixing.
Necessary materials and tools:
Ethanol(l), hexane(l), distilled water, potassium carbonate(s) copper sulphate(s), sodium(s), iodine(s), potassium(s), 3 pipettes, large and small test tubes, thermometer, beaker and conical flask.
- Before the water was added into a large test tube by the pipette, the thermometer was measured. Then 1cm³ of ethanol was added into the tube by another pipette. The tube was shaken gently and the observation was noted. The temperature of the large test tube was measured.
- 1cm3 of water and 1cm3 of hexane were placed into the same test tube, using different pipettes. The test tube was shaken gently and observed. The change of temperature was noted.
- 1cm3 of ethanol and 1cm3 of hexane were poured into the same test tube using different pipettes. The test tube was shaken gently and the observation and temperature change were noted. A further 1cm3 of ethanol was added into the tube.
- Some potassium carbonate was placed into the tube from test 1 using a spatula. The tube was shaken and observed.
- 1cm3 of water, 1cm3 of ethanol and 1cm3 of hexane were poured into three large test tubes. A small amount of copper sulphate was added into each tube by using a spatula. The tubes were shaken and observations noted.
- 1cm3 of water, 1cm3 of ethanol and 1cm3 of hexane were added into three large test tubes. A small amount of iodine was added into each tube by using a spatula. The tubes were shaken and the observation was noted.
- About 75cm of water was poured into the conical flask then a piece of sodium was placed into it by using tweezers. The observation was noted.
Mixing liquids and solids
Reaction of sodium with water
From the results, it can be seen that the dissolution rates of different solutes mixed in different solvents are not the same. According to baidubaike(2009), materials dissolved or not and the solubility of the size, on the one hand is determined by the characteristics of materials themselves (solvent and solute) and on the other hand, affected by the external conditions, such as temperature, pressure, solvents etc. In these tests, the external conditions were almost the same, so the differences were from the materials themselves.
It's worth mentioning that the iodine did not seem to dissolve in water, but did in ethanol and hexane. Theoretically, iodine can dissolve in water but a very low rate because of weak forces in Iodine, temporary dipoles or Van der Waals. According to the K12 chemistry forum (2009), its solubility of Iodine in water is 1 molecule to 2950 water molecules. Iodine can dissolve in Ethanol and Hexane because of the organic chains. They have Van der Waals force.
The reaction of sodium with water is interesting. The piece of sodium became a small silver ball and burned as it rushed around the water surface. It seemed that it wanted to escape out of the conical flask. The ball became smaller and smaller. At last, it disappeared and a smelly odor was produced.
Symbols: 2Na(s) + 2H2O(l) ?2NaOH(aq) + H2
After doing these experiments, many skills of using laboratory tools were known perfected. I found that water is an excellent solvent and it can dissolve many materials.
- Hydrogen Bonds, 2003 [online] http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/H/HydrogenBonds.html Baidubaike, 2009 [online] http://baike.baidu.com/view/2826349.htm?fr=ala0 (25-Nov-2009)
- RS.C, (no date) [online] http://www.rsc.org/education/teachers/learnnet/pdf/learnnet/nc/tc_nc2.pdf (25-Nov-2009)
- Van der Waals Forces and Equation, (no date) [online] http://www.kentchemistry.com/links/bonding/vdw.htm (07-Dec-2009)