Purpose: To demonstrate the density characteristic at its given temperature and pressure. By measuring the liquid’s mass and volume, density can be determined with its physical property and its specific value.
Theory: The mass and the volume of any object can be measured. However, the separate measurements do not tell us how tightly packed the substance might be. If we compare the mass of the object to its volume, we obtain a relationship called density. The density was calculated by dividing the mass of the cube by its volume. The independent variable in this experiment is the volume of the liquid, while the dependent variable is the density of the material. Two important control variables in this experiment are the material and the shape of the test samples.
The Important reactions are:
Density = Mass of Substance__ Volume of Substance
1.) Determination of the density of a metal
• Obtain a metal slug then record its weight.
• Fill a 50mL using a graduated cylinder → record its weight; then roll the metal slug into the cylinder → record weight on the data. Repeat to get 3 trial samples.
2.) Calibration of pipets
• Measure the mass of a clean & dry 50mL Erlenmeyer flask with a stopper
• Using a pipet, measure 10mL of deionized water then pour into weighed flask /stopper.
• Repeat to get 3 trial samples. Obtain the water temperature → record necessary data.
3.) Determination of the density of a liquid
• Obtain about 40mL unknown liquid→ record the unknown number for the liquid.
• Using a pipet, measure 10mL of unknown liquid then pour into weighed flask /stopper and weight unknown liquid with it → record weight on the data.
• Repeat to get 3 trial samples. → record weight on the data.
Problems Encountered/Sources of Error:
A source of error in this experiment is the measurement of the volume of the water after dropping the metal slug. When the metal slug was dropped into the graduated cylinder water tended to splash out. This made the volume of the slug smaller than it really was and the density of the cube larger than the actual value.
Discussion of Results and Conclusions:
Based on the results of different liquids/substances that we used and the three trial samples; the result of this experiment show that changing the volume of a liquid does not affect the density of the material. Measurements will be performed on three samples of water to improve precision and accuracy. Mass will be measured with an electronic balance, in grams (g), and volume will be measured directly with a graduated cylinder, in milliliters (mL). Recall that when measuring liquid volumes, the graduated scale must be read from the lowest point of the curved surface of the liquid (the meniscus). The accuracy of the experimentally determined density of water will then be evaluated by comparison to the true, accepted density of water.
Post Lab Questions:
1. ) GIVEN: The initial mass is 34.5 kg = 3450g
Volume = 3450g * (mL / 13.6g) = 253.68mL
2.) Since the flask that we used initially was not completely dry, it may create some discrepancies in our data entry. Nevertheless, the Erlenmeyer flask has calibration lines every 50 mL between 200 and 500 mL. ; therefore, the error maybe within ±5%. To determine the size of the flask needed during an experiment, determine the maximum amount of liquid the flask needs to contain. Multiply that number by two and select a flask size that comes closest to that number.
3.) He had under estimated the weight of the bag of sand. Since the gold is much heavier in mass weight he was not successful in fooling the tomb. He could have put more sand into the bag to get the same weight as the gold but it may take him longer to gather more sand or he may need a whole lot of bags of sand to have a substantial weight as the gold.