# Pipetting, Weighing, Accuracy and Plotting

Topics: Pipette, Volumetric pipettes, Liquid Pages: 4 (1287 words) Published: February 23, 2013
Pipetting, weighing, accuracy and plotting
Introduction
The aim of this experiment was to determine the density of water and, of unknown solutions, by being as accurate as possible, by pipetting and weighing the solutions. Density if defined as “The mass per unit volume of substance; common unitg cm-3” (Lewis. R and Evans. W., 2011). As the density is an intensive property of all matter it depends on temperature and pressure. “The density of a mixture may also depend on its composition” (Nedelsky. L., 1983). Density of a matter can be calculated by: Density= Mass (g)Valume(cm3)=g cm-3

Pipette is a scientific tool, used in labs to drain off liquids to transfer it from a place/container to another for different purposes. There are different types of pipettes; ones which were used in this practical were serological and mechanical pipettes. Mechanical pipettes are volumetric pipettes which are used to transfer a specific volume of solution/liquid. The capacity of mechanical pipettes varies depending on the pipette itself. Serological pipettes are also measuring pipette which have gradients that continue down all the way in to the tip of the pipette. A pipette dispenser must be used to drain off liquid by serological pipette. Mechanical pipette are used to measure small amount of liquids and are very accurate whereas serological pipette are used to measure large amount of solutions and are not as accurate as mechanical pipettes. During this experiments accuracy, consistency and precision was essential by recording the results in correct decimal places and significant figures and, by plotting the results on the right format of a graph. It was crucial to decide which type of pipette, either Serological or mechanical pipette to use for different amount of solutions, as one type of pipette, for example, P-200 could not be used to measure more than 200μl of solution. Therefore, one type of pipette could not be used to measure different amount of solution. Material...