# Laboratory Techniques and Measurements

Topics: Density, Water Pages: 7 (2302 words) Published: March 2, 2013

General Chemistry 1
Lab 1: Laboratory Techniques and Measurements

Purpose: The purpose of this lab is to ensure that students are able to understand how to conduct measurements of length, mass, temperature, density and volume using different measuring devices. Students will also learn how to dilute substances by using simple algebra.

Procedure:
1. Prepare a data table similar to Data Table 1 shown below. 2. Choose any three objects that are shorter than the metric ruler to measure, such as a CD, key, spoon, etc. a. Measure the objects’ lengths in centimeters. Estimate to one decimal place. Record the measurements in Data Table 1. b. Measure the objects’ lengths in millimeters. Estimate to one decimal place. Record the measurements in Data Table 1. Warm Temperature Measurements

NOTE: If a stove is available, simplify this exercise by bringing the water to a boil in a pot on the stove, instead of in the 100 mL beaker over the burner fuel. 1. Prepare a data table similar to Data Table 2 shown below. 2. Fill a 100 mL beaker with 50 mL of hot tap water. Get the water as hot as possible. 3. Use a thermometer to measure the temperature of the water in the beaker using Celsius units. Record the measurements in Data Table 2. 4. Place the beaker of water on the wire gauze burner stand. 5. Remove the cap from the burner fuel and set it aside. Light the fuel and slip it under the burner stand. Note: when lit, the flame may be barely visible. 6. Bring the water to a full boil and record its temperature. Record the measurement in Data Table 2. 7. Let the water boil for about 5 minutes. Record the temperature in Data Table 2. 8. Extinguish the burner fuel by placing the lid loosely on the can to cut off the air supply. Let the fuel can cool before screwing on the lid. If the lid is screwed on while the fuel is hot, it can create a vacuum and make opening the can difficult in the future. Cold Temperature Measurements

1. Allow the 100 mL beaker to cool. Fill the beaker with cold tap water and then record the water temperature in Data Table 2. 2. Prepare an ice water bath by adding ice to the beaker filled with cold tap water. It may be necessary to pour out some of the water to make room for the ice. 3. Immerse the thermometer in the ice bath and stir gently. Record the temperature in Data Table 2. 4. Let the ice water stand for about 5 minutes. Then record the temperature in Data Table 2. To get an accurate measurement, ice should still be present in the water. Volume Measurements

1. Prepare a data table similar to Data Table 3 shown below. 2. Fill a small test tube with water.
3. Pour the water from the test tube into the 25 mL graduated cylinder. Record the volume of water in Data Table 3. Empty the graduated cylinder. 4. Determine the volume of a thin-stemmed pipet:

a) Completely fill a clean, empty pipet with water.
b) Hold the pipet vertically and add the water drop-by-drop to a graduated cylinder until the water reaches the 1 mL mark. Count the number of drops in 1 mL. Record the data in Data Table 3. c) Squeeze the pipet multiple times to expel all the water into the graduated cylinder and return it to its auxiliary bag. Record the volume reading of the graduated cylinder in Data Table 3. Mass Measurements

1. Prepare a data table similar to Data Table 4 shown below. 2. When measuring chemicals, the surface of the scale must be protected with paper. The mass of the paper will add to the mass of the object to be measured, so the mass must be eliminated by taring the scale to set the scale to zero. Cut a piece of paper approximately 5 cm x 5 cm in size so it can be placed on the scale. Place this piece of paper on the scale and press the tare button. 3. Choose seven objects to measure. Remember, the scale can weigh a maximum mass of 500 grams or 18 ounces. 4. Record the hypothesized mass of the first object in Data Table 4. 5. Use...