Lab Report : Lab # 2
T.A: Thushara Samarasinghe
Chem 184 Spring 2013, Section : 315
When a kernel of popcorn is heated, pressure builds and, depending on the percent of water in the kernel, the kernel pops open and popcorn is produced. The percentage of water in each kernel differs between brands of popcorn. If the steam produced fails to pop the kernel, the kernel becomes hard and burns. The purpose of Part 1, “Popcorn Composition”, of the “Composition and Separations Lab was to determine whether premium popcorn brands display desirable qualities when measured and compared with cheaper brands of popcorn. The experimental relevance of Part 1 of the experiment was to demonstrate the effects of water in a popcorn kernel when heated and converted to heat. Differences in water percentage determine whether or not the kernel will burst and create popcorn. In Part 2, “Separating a Solid Mixture”, the purpose was to work with supplies in the lab to separate a solid mixture of popcorn, sand, salt and iron filings into the four separate components to eventually learn the percent composition of the solid mixture. By developing a plan to separate the mixture, the group should have ended up with four separate items with weights that added up to the original weight of the mixture. The experimental relevance of Part 2 of the experiment was to learn how to separate each component in a four part solid mixture from each other. Procedure:
In part 1 of this week’s lab three popcorn kernels of a one brand were given to each group. A Bunsen burner was set up by each group and the three kernels were each weighed separately on an electric balance. The Bunsen burner was then lit following the instructions given. (ch185) A 100mL beaker was obtained and filled with a half inch of clean sand. The beaker was placed on a ring stand and one kernel of popcorn was submerged into the sand. The beaker was then covered with a watch glass and heated over the Bunsen burner until the kernel popped. After popping, the kernel was removed and weighed and the moisture content was measured. This procedure occurred for all three kernels. After the moisture content of all three kernels were measured, an average was deduced for the three and written on the board. Each of the other four groups also wrote their averages for their individual brand on the board to give the class a better understanding of the differences in moisture content for each of the five brands. In part 2 of this week’s lab, a 50mL beaker was filled with a solid mixture consisting of popcorn, sand, salt and iron filings. The group then got the mass of the entire mixture and began sketching a plan to separate the mixture properly into its original four contents. First the group separated the popcorn from the mixture by using a drainer. The popcorn was then weighed. Second, the iron filings were separated using a magnet after pouring the remaining mixture onto a piece of paper. After the magnet collected all iron, the iron was scraped into a beaker and the weight was recorded. The third and final separation used a beaker and a filter paper. The filter paper was weighed and put into a filter that spilt into the beaker. The remaining salt/sand mixture was then poured into the filter paper using water to dissolve the salt. After the solution was put into the filter paper and the salt had dissolved, the filter paper and sand was dried and then weighed. After subtracting the filter paper weight from the weight of the filter paper and sand together, the weight of the sand was known. Once you had the weight of the sand, iron and popcorn, the weight of the salt was found by subtracting the three combined weights from the original weight of the mixture. To find the percent composition of each component, the weight of each was divided by 100 and, in the end, each components percent added up to 100% of the initial...