# Basic Laboratory Techniques

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Objectives

1. To use common laboratory apparatus in measuring mass, length, volume, temperature, and density

2. To compute the accuracy and the precision of a set of scientific measurements

3. To apply the concept of significant figures in reporting correctly scientific measurements Materials and Equipment

Ruler, meter stick, 10 mL graduated cylinder, 50 mL graduated cylinder, small and large test tube, 50 mL and 150 mL beakers, 50 mL Erlenmeyer flask, digital top-loading balance, unknown liquids for density determination, irregular solids for density determination, safety glasses, Lab manual that was used for measurement. Introduction

The International System of Measurement (SI) is used worldwide and has been adopted as the official system of measurement by most countries. It is commonly called the metric system. Our traditional American/English system of measurement (miles, quarts, pounds) requires many conversion factors. Take length, for example – there are inches, feet, yards, rods, chains, and miles. The metric system is much different. It is based on standard units that can be easily converted by multiplying or dividing by factors of ten. Engineers and scientists most often use these standard metric units: the meter, for length; the gram, for mass (or weight); the liter, for volume; and the degree Celsius (or less often Kelvin) for temperature.

In common English, we often use the terms “accuracy” and “precision” interchangeably, to indicate how “correct” an answer is. However, in science the two terms have different meanings. Accuracy is a measure of how closely an observation is to the “true” or “accepted” value. Precision is a measure of how closely a group of observations are to one another. For example, about a dartboard, “accurate” would be hitting the bulls-eye or center of the target; “precise” would mean that all of your darts hit the target close to one another, without reference to whether or not you hit the bulls-eye. So, it is possible to be precise (all the darts close together) but not accurate (missing the bulls-eye). Of course, we would like to be both accurate and precise in our laboratory measurements.

Observation

Length were determined and utilized all the correct conversion according to the SI units Derivation of meter (or meter), m; also mm, cm, dm, µm, nm, km. We have written metric equalities using various derived length units as the following: 1 m = 102 cm and the equivalent 10-2 m = 1 cm

1 km = 103 m and 10-3 km = 1 m

1 nm = 10-9 m and 1 m = 10+9 nm

1 m = 100 cm or 1 cm = 10-2 m

1 g = 106 µg or 1 µg = 10-6 µg

1 L = 103 mL or 1 mL = 10-3 L

Discussion

We have made numerous calculation errors, but utilizing the conversion tale from the lab manual assisted us determining the true value. All important calculation were noted by the professor and the value was incorporated with our final result.

Conclusion

This experiment helped us how to use basic laboratory apparatus in measuring mass, length, volume, temperature and density. By the use of these measurements, we learned how to compute the accuracy and precision of the results and proper way in reporting in significant figures. In performing this experiment number 1, Basic Laboratory Techniques, I conclude that in doing laboratory experiment, you are required to have a careful and keen observation plus proper and right laboratory techniques and operations to obtain correct results. Furthermore, using the correct formulas in computing accuracy and precision and reporting it on a right way by using the rules on scientific notation.

References

Chemistry: The Central Science 12th edition Laboratory Manual 2012 Brown et al.