EXPERIMENT #2 INTRODUCTION TO MEASUREMENTS AND GRAPHING. illustrate the overall scope of the experiment or procedure utilized.

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1 Introduction In science, precise measurements are essential to the accuracy of scientific studies. Measurements in science can involve complex machinery beyond the simple ruler or scale. Devices, such as a spectrophotmeter, can measure such things as the amount of light absorbed by a compound. In science, themetric system is the preferred measurement tool due to its uniform incremental nature, and The ability to collect accurate data is only a step in the process of scientific discovery. Once the data is collected, the presentation of these measurements can take on many forms: written, verbal, or visual. Graphing is one of the easiest visual techniques to illustrate the overall scope of the experiment or procedure utilized. Goals At the end of this laboratory, you will: 1. Have developed a thorough understanding of the metric system. 2. Have learned the proper handling and use of the quadruple-beam scale. 3. Have the knowledge to construct and explain a proper graph.

2 A. Conversions Utilizing data obtained from your lab instructor, you will convert the following data: 1. Mass of an object from kilograms into pounds. 2. Length of an object from centimeters into millimeters. 3. Length of an object from centimeters t or millimeters into inches. Example: Given that 1 inch = 2.54 centimeters, convert 23 inches into centimeters 23 inches x (2.54 centimeters / 1 inch) = 58.4 centimeters Please see lab exercise #1 for dimensional analysis procedure and additional examples!

3 s B. Area Area is a two-dimensional condition and is expressed as a square of the unit of measure. To find the surface area of an object you multiply the length of an object by its width. AREA = length x width Example: A plot of land has a length of 2.3 kilometers by a width of 3.3 kilometers. What is the total surface area of this plot of land? AREA = 2.3 kilometers x 3.3 kilometers = 7.6 square kilometers Utilizing data obtained from your lab instructor, you will: 1. Calculate the surface area of an object in square centimeters. 2. Convert the surface area measurements from square centimeters into square inches.

4 C. Volume of a box Volume is a three-dimensional condition and is expressed as the cubic of the unit of measure. The volume of an object is simply the length multiplied by the width multiplied by the height. VOLUME = length x width x height Example: A rectangular box has the following dimensions: length = 2.3 centimeters, width = 1.2 centimeters, and height = 3.9 centimeters. What is the volume of this box? VOLUME = 2.3 centimeters x 1.2 centimeters x 3.9 centimeters = 10.8 cubic centimeters Utilizing data obtained from your lab instructor, you will: 1. Calculate the volume of an object in cubic centimeters.

5 C. Volume of a cylinder Volume is a three-dimensional condition and is expressed as the cubic of the unit of measure. Since many biological structures are cylindrical in shape, the volume of a cylinder is a critical formula to know. In order to determine the volume of a cylinder you need to first know the surface area of the circle that makes up the end of the cylinder. AREA OF A CIRCLE = π x r 2 where π = 3.14 and r = radius of the circle (1/2 the diameter of a circle) The volume is then the area of the circle multiplied by the length or height of the cylinder VOLUME = π x r 2 x height Example: A cylinder has a radius of 10.8 centimeters and a height of 4.3 centimeters. What is the volume of the cylinder? VOLUME = 3.14 x 10.8 centimeters x 10.8 centimeters x 4.3 centimeters = cubic VOLUME 3.14 x 10.8 centimeters x 10.8 centimeters x 4.3 centimeters cubic centimeters

6 C. Volume of a cylinder (continued) Utilizing data obtained from your lab instructor, you will: 1. Calculate the radius of a circle at the end of a cylinder in centimeters. 2. Calculate the surface area of a circle at the end of a cylinder in square centimeters. 3. Calculate the volume of a cylinder in cubic centimeters.

7 D. Measurements of blocks This section will utilize the previous techniques to determine the linear dimensions, surface areas, and volumes of wooden blocks. When you enter lab, you will find three distinct groups of wooden blocks. You will choose one block from each of the three groups and perform the following measurements on them: 1. Measure the length, width, and height ht of each wooden block to the nearest 0.1 centimeters. t

8 D. Measurements of blocks (continued) 2. Calculate the three surface areas for each block in square centimeters 3. Calculate the volume for each block in cubic centimeters.

9 E. Mass of the wooden blocks In addition to measuring and calculating the wooden blocks linear dimensions, surface areas, and volumes, you will also be measuring each blocks weight or mass, using the quadruple beam mechanical balance. The blocks used in section D must be used for the mass measurements, so that we can calculate density in section F. Quadruple beam mechanical balance

10 E. Mass of the wooden blocks (continued) The balance is accurate to the nearest 0.01 grams (g). The following slides will familiarize yourself with the proper use of the balance. 1. The balance utilizes four balance beams with the following range of weights: A g in 100 g increments B gin 10 g increments C g in 1 g increments D. 0-1 g in 0.01 g increments

11 E. Mass of the wooden blocks (continued) 2. When no objects are placed on the scale, the swing-arm s pointer is aligned with the white line on the right hand side, indicating that the scale is balanced. 3. Once an object is placed on the scale, the pointer deflects upwards indicating an unbalanced condition. 4. The weights on the four balancing arms are moved one at a time to re-balance the scale with the object in place. 5. Whenever the pointer deflects below the line, this indicates that the counter weights exceed the object s weight and thus the weights must be moved back to a lower weight. 6. The next slide will illustrate the proper methodical use of the scale. A) Pay close attention to the sequence of counter-weight movements B) Notice how we begin with the heavier weights and end with the lightest weight C) Notice how we allow the pointer to deflect downward, then move the weight back a notch before proceeding to the next lower weighted beam.

12 1 2 Click on each picture to see the movies! 3

13 F. Density calculations Using the volume calculations from part D and the weights from part E, you will be able to compute the density of your wooden blocks. Density is expressed in units of mass over volume. Since your mass measurements were in units of grams and your volume calculations in units of cubic centimeters, your answer will be expressed in grams per cubic centimeter. t Example: Block s volume = 550 cubic centimeters, Block s mass = 95.4 grams Block s density = 95.4 grams / 550 cubic centimeters = grams / cubic centimeter

14 G. Introduction to Graphing Graphing is an easy and descriptive way to present experimental data. As in most experiments, there are two variables, one known before the experiment (INDEPENDENT) and the other after the experiment is completed (DEPENDENT). When constructing a graph, the DEPENDENT variable is always plotted on the Y-AXIS (VERTICAL) and the INDEPENDENT variable is always plotted on the X-AXIS (HORIZONTAL). Please refer to the graphs on the following pages and in your lab manual to familiarize yourself with graphing. Y-Axis = Dependent Variable X-Axis = Independent Variable

15 G. Introduction to Graphing Rainfall (inches) Average Rainfall in Glendora J A S O N D J F M Months (by First Lettter)

16 G. Introduction to Graphing The Effects of Chemical Agents on Bacteria Number of Surviving Bacteria Time ( Minutes)

17 G. Introduction to Graphing As you looked at the sample graphs, you may have noticed that they came in two flavors : 1) A point-to-point to graph in which the data points are connected directly to one another, and 2) A best fit line in which a line is drawn through the graph to best represent the data collected. The point-to-point graph is used to illustrate non-linear data, where the dependent and independent d variables are not proportional lto each other. The best fit line graph is used to illustrate linear data, where the dependent and independent variables are proportional to each other, which allows the experimenter to predict the outcome of an experiment. Example: Look at the following graph on the following page!

18 G. Introduction to Graphing The Effects of Chemical Agents on Bacteria Number of Surviving Bacteria Time ( Minutes) Based on the best fit line shown, at what time will there be no surviving bacteria? 41 MINUTES

19 Conclusions Hopefully, this tutorial has been insightful for the upcoming laboratory. You should be prepared for the following tasks: 1. Using the metric system for measurements and calculations. 2. The proper use of a quadruple-beam scale. 3. The construction of a proper p graph.