Lab question

Lab 2: Properties of Matter - Density

Pre‐lab Questions

1. What can cause the density of the same substance to change?

1. List two possible hazards in this laboratory experiment.

1. A gold‐colored ring is found to weigh 2.542 g at 20 °C. The ring is dropped into a graduated cylinder filled with water, and is found to displace 0.33 mL of liquid. The density of 14 carat gold ranges from 12.9 - 14.6 g/mL at 20 °C. Is the ring made of gold? Explain your answer.

Experiment: Determination of Density

Procedure

**Take photographs of your experiment set up for Part 1 and 2, and for your results. Submit them with your laboratory report.**

Part 1: Density of Common Metals

1. Weigh out 10 washers and record their mass in the Data and Calculations section.

2. Determine the volume of the washers by their water displacement in a graduated cylinder. Fill a 10 mL graduated cylinder up to the 5.0 mL mark with distilled water. Tilt the graduated cylinder to provide a slope for the washers to come down. GENTLY drop the washers into the graduated cylinder so that no water is splashed out. Gently tap the graduated cylinder until there are no more air bubbles around the washers. Record the difference between the initial and final volume of water in the graduated cylinder to the 0.2 mL place.

3. Determine the density of the washers using the formula: D = m/V.

4. Compare the density of your washers to the densities of different metals found in Table1: Densities of Some Common Metals. Determine which metal your washers are made out of and record this in the Data section.

Table 1: Sample Densities of Common Metals

Part 2: Density of Plastics

1. Make a density column in the 10 mL graduated cylinder (Figure 4) with the following steps:

1. Use the pipette to measure 3 mL of 1 M calcium chloride solution, and pipette into the 10 mL graduated cylinder. You may have to pipette 1 mL at a time for better precision. This solution has a density of 1.1 g/mL.

2. Pour about 10 mL of distilled water into a 50 mL beaker. Allow 1 drop of food coloring to mix with the water, swirling the beaker to ensure an even mixture. Measure 3 mL of dyed distilled water into the pipette. Again, you may have to pipette 1 mL at a time.

3. Slowly add the 3 mL of dyed distilled water into the density column so that the water layer rests on top of the calcium chloride layer. Water has a density of 1.00 g / mL.

Hint: Add one drop at a time, very slowly to get the best results.

1. Use the pipette to measure 3 mL of ethanol. Slowly, one drop at a time, add the ethanol into the density column so that the ethanol rests on top of the water layer. Ethanol has a density of 0.80 g / mL.

1. Use scissors to cut a piece of the coffee stirrer that can fit into the 10 mL graduated cylinder.

2. Use scissors to cut a piece of the bowl of the plastic spoon so that can fit into the 10 mL graduated cylinder.

3. Use scissors to cut a piece of the rim of the Styrofoam© cup so that can fit into the 10 mL graduated cylinder.

HINT: It is best if all pieces of plastic are similar in size.

1. Gently drop the pieces of each plastic in the plastic mixture one-by-one into the cylinder.

2. Observe where each object situates within the cylinder.

3. In the Data section, record the location of each type of plastic in the gradient.

HINT: Make observations quickly, but watch the objects for a couple minutes. They may make gradual movement up and down the column.

1. Clean-up the work area and dispose of column down the sink with plenty of water.

Data and Calculations

Procedure 1:

Mass of sample washers:

Initial volume of water:

Final volume of water:

Change in volume of water:

Density of washers:

Procedure 2:

 Table 2: Observations of Plastics

Post‐lab Questions

1. Take photographs of your experimental set up for Part 1 and Part 2, and your results. Submit them with your laboratory report.

2. What material did you determine your washers are made from? Why did you decide your sample washers are made out of this metal?

3. Why is the calcium chloride solution poured into the density column first?

4. Which type of plastic is most dense? Which type is the least dense? Explain.

5. How could you use a density gradient column to help identify whether a toy car is made with more metal or more plastic?

©eScience Labs, 2013