Lab 4 How Can We Use a Physical Property to Develop a Separation Method Tuesday January 29 2019 11 58 AM Lab 4 How Can We Use a Physical Property to Develop a Separation Method Total Pts earned out of 15 on this lab report Lab 4 25 pts consists of the following 1 2 A pre lab assignment found on Brightspace 5 pts A Lab Report consisting of a b c Two Activity items 4 pts Three Question items 5 pts Three Calculation items 6 pts 3 A post lab problem set found on Brightspace 5 pts GOALS LAB LEARNING OBJECTIVES The goal of this lab is to understand how the physical property of density can be used to separate plastic materials 1 2 3 Determine a solid s volume using water displacement method Determine whether a substance will float sink in a liquid from based on the densities of the substance and the liquid Be able to select proper separation method from the given physical properties of the components of a mixture Click here to Watch Video 1 in your browser INTRODUCTION Labs Page 1 Density is the amount of mass per unit of volume or the mass divided by the volume density mass volume Density is an intrinsic property of a substance meaning the density is the same no matter how much of the substance is present The mass and the volume of a substance are proportional to each other thus the value of the density remains the same when you change the amount of substance present The density of a liquid depends on the temperature of the liquid and the concentration of any substances dissolved in the liquid solutes Pure water has a density of about 1 0 g mL at 4 C The density of water decreases as the temperature increases Dissolving salt in water often increases the density of the solution because the overall mass of the solution increases without much change in the volume For example a saturated sodium chloride solution has a density of about 1 2 g mL To determine the density of an object you need to find the mass and the volume of the object In lab we find the mass of an object using an analytical balance One of the simplest ways to measure the volume of an object is by liquid displacement If the object completely sinks in the liquid then the volume of the object is equal to the amount of liquid it displaces If the object floats in the liquid then it will NOT displace a volume of liquid equal to its volume since a portion of the object is above the liquid In this case the density cannot be determined by liquid displacement Your first task in this exercise is to explore how density is related to sinking and floating as you determine the density of six types of plastic using deionized water and ethanol You will then compare your experimental densities to known densities see Table 4 1 below and calculate the error of each density result Your second task is to separate two types of recyclable plastics using the physical property of density Table 4 1 Six types of plastic used in this experiment Type of plastic Abbreviation Recycling Code Approximate high density polyethylene low density polyethylene HDPE LDPE 2 4 Labs Page 2 length of plastic sample 3 0 cm 2 5 cm low density polyethylene polyester polyethylene terephthalate polypropylene polystyrene polyvinyl chloride LDPE PET PP PS PVC 4 1 5 6 3 2 5 cm 1 0 cm 3 5 cm 2 0 cm 1 5 cm SAFETY Ethanol 100 is extremely flammable No flames are allowed in the laboratory Caution Use a snorkel when working with ethanol All ethanol solutions must be discarded in the waste jar in the main hood PROCEDURE PART A DENSITY SINKING AND FLOATING Material required 6 different plastic pieces HDPE LDPE PET PP PS PVC Deionized water 50 mL 100 ethanol 1 Obtain samples of the six types of plastics Make sure that each type of plastic is completely dry 2 Measure and record the mass g of each object Use the same balance for each of your measurements The masses of each plastic piece are as follows Labs Page 3 PET 0 8858 g PVC 1 3443 g PS 1 4596 g LDPE 1 6479 g HDPE 2 2894 g PP 2 6772 g Density Determination with Deionized Water Determine the volume mL of each plastic by water displacement if possible using the following process Note The density of deionized water at room temperature is approximately 1 0 g mL 1 Add enough water to a 50 mL graduated cylinder to allow the piece of plastic to submerge completely and still have a total volume less than the maximum capacity of the cylinder See Figure 1 Labs Page 4 Figure 1 Only water When determining the volume of water in a graduated cylinder the volume should be read from the bottom of the meniscus the curvature of the water at the surface The graduated cylinders pictured in this lab can be read to one decimal place For example the graphic below shows a value about half way between 21 0 mL and 22 0 mL so we report the value to our best judgement as 21 5 mL Labs Page 5 Question 1 1 pt By zooming in on Figure 1 one can see where the meniscus is located indicated by the arrow Determine the volume of the water in Figure 1 to the correct number of significant figures and units Pts Earned Volume 40 1 mL 2 Tilt the cylinder and then carefully add the piece of plastic to the cylinder Allow the plastic to slide down the side of the cylinder to avoid splashing the liquid or cracking the cylinder Note In each figure below the initial volume of the water in the graduated cylinder was adjusted to be the same as the volume in Figure 1 Figure 2 a A piece of PET in water b A piece of PVC in water Labs Page 6 Figure 3 a A piece of LDPE in water b A piece of PS in water Figure 4 a A piece of HDPE in water b A piece of PP in water Labs Page 7 Calculation 1 2 pts Insert a Table in this answer box The table should be titled Density Determined by Displacement of Deionized Water and have six labeled columns type of plastic mass g initial volume mL final volume mL volume displaced mL and density g mL Pieces that float may have suspect volume readings indicate this by changing their densities values to red text in your table Pts Earned To receive full credit you must compute your density values to the correct number of significant figures and units Hint Zoom in on the six graduated cylinders pictured in Figures 2 4 to determined the final volume after adding the plastic to the graduated cylinder Density Determined by Displacement of Deionized Water Plastic mass g initial volume mL final volume mL volume displaced mL density g mL PET PVC LDPE PS …