Lab #1: Introduction to Lab Techniques INTRODUCTION

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1 Name Lab #1: Introduction to Lab Techniques INTRODUCTION Our goals in this experiment are (1) to make some measurements using a metric ruler, (2) to learn how to determine volumes with a graduated cylinder, and (3) to determine the density of an unknown liquid and an unknown solid. PROCEDURE A. The Metric Ruler i) On the image of the metric ruler below, draw a small arrow pointing to 2.00 cm and write A, do the same and write B" at cm, "C" at 3.50 cm, "D" at 8.55 cm, and E" at cm. NOTE: The numbers that are displayed are cm, the increment is 0.1 cm. ii) Use a metric ruler to determine the length and width of this piece of paper. Metric rulers are on the counter in the front of the lab. Use the correct number of decimal places base on the ruler increments (as you did in the pre-lab). Increment on metric ruler = cm Length of the page = cm Do calculations to convert the length of the page to mm and meter (show your calculations for full credit) = mm = m. Width of the page = cm Do calculations to convert the width of the page to mm and meter (show your calculations for full credit) = mm = m. 1

2 B. The Graduated Cylinder There are 3 graduated cylinders set up in the lab. Each line on the 1000mL graduated cylinder represents ten milliliters (note that 1000 ml = 1 L). Each line on the 100mL graduated cylinder represents one milliliter. Each line on the 10 ml graduated cylinder represents 0.1 milliliters. Observe the top of the liquid in the 100 ml cylinder. Note that the liquid surface is curved, not level. The curved surface is called the meniscus. The volume is always read at the lowest point of the meniscus. Hold the graduated cylinder so the meniscus is exactly at eye level. Now raise and lower the graduated cylinder and observe that the volume reading changes as the cylinder is raised and lowered. Only when your eye is at exactly the same level as the bottom of the meniscus can you obtain an accurate volume reading. (The error introduced if your eye is high or low is called parallax.) Using the correct number of decimal places (as you did in the pre-lab), determine the volume of liquid in each of the 3 cylinders and record the data below. Graduate Cylinder 1000 ml (= 1L) Increment of Graduated Cylinder Volume of Liquid in Cylinder 100 ml 10 ml Remember to use units whenever you write a number. 2

3 C. Measuring the Density of a Solid and of a Liquid i) Density of a metal cylinder 1) Each student will be given a metal cylinder, record the unknown number in the table below. 2) Weigh the metal cylinder, record the mass (in table below) to at least three places past the decimal. 3) Determine the increment of the 100 ml graduated cylinder and record it in the table below. 4) Place about 30 ml of water in your 100 ml graduated cylinder, record the volume to one decimal place more precise than the increment (as done in pre-lab) in the table below. 5) While holding the graduated cylinder at an angle, carefully slide your metal slug into the graduated cylinder. The metal cylinder must be completely submerged. Record the new volume to one decimal place more precise than the increment in the table below. 6) Calculate the volume of your metal cylinder. 7) Go to page 5 and calculate the density of your metal cylinder. Show your calculations, using the correct number of significant figurers in the appropriate box on page 5. Metal Cylinder: Unknown number:.... Mass of metal... g Increment on a 100 ml graduated cylinder.. ml (Figure it out just as you did on the prelab or ruler) Volume before submersion of metal..... ml (report volume to one decimal place more precise than the increment) Volume after submersion of metal.... ml (report volume to one decimal place more precise than the increment) Calculate the volume of the metal (Use the data above and the volume by displacement method as discussed in the powerpoint prelab introduction to calculate the volume of the metal) = ml 3

4 ii) Density of a liquid 1) Obtain an unknown liquid from the instructor and record the number of the unknown on the data table below. 2) Determine the increment of the 10 ml graduated cylinder and record it in the table below. Note that the increment is different for the 10ml graduated cylinder than it was for the 100 ml graduated cylinder that was used for the metal slug. 3) Measure and record, in the table below, the mass of a clean, dry 10 ml graduated cylinder using a balance. Record the mass to at least three places past the decimal. 4) Pour between 5 and 10 ml of the unknown liquid in the 10 ml graduated cylinder. Re-weigh and record the mass, to at least three places past the decimal, in the table below. 5) Next, record the volume of the unknown liquid in the 10 ml cylinder to one decimal place more precise than the increment. If you need to redo the density of your unknown liquid, the cylinder must be completely dry before you weigh it. The graduated cylinder can be dried using a rolled-up paper towel. 6) Calculate the mass of your unknown liquid. 7) Go to page 5 and calculate the density of your unknown liquid. Show your calculations, using the correct number of significant figurers in the appropriate box on page 5. Unknown liquid: Unknown number:. Increment on a 10 ml graduated cylinder.. ml (Figure it out just as you did on the prelab or ruler) Mass of 10 ml graduated cylinder.. g Mass of 10 ml graduated cylinder + liquid g Volume of liquid. ml (Report volume to one decimal place more precise than the increment.) Calculate the mass of the liquid (Calculated using weight by difference method) = g 4

5 DENSITY CALCULATIONS In the area below, calculate the densities of the metal cylinder and the unknown liquid. Remember: Every number in a measurement must have a number and a unit) i) Calculation of the unknown solid s density Unknown solid number Density of your unknown solid Did you use the correct number of significant figures? ii) Calculation of the unknown liquid s density Unknown liquid number Density of your unknown liquid Did you use the correct number of significant figures? 5