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Significant Figures and Lab Data Mark as Favorite (45 Favorites)

LAB in Density, Accuracy, Measurements, Significant Figures. Last updated April 22, 2019.

Summary

In this lesson, students will use laboratory equipment of different precision to collect data for several different metals, and then use the data to calculate the density of each. They will then compare their calculated densities to accepted values and determine the combination of equipment that leads to the most accurate calculation of density.

Middle or high school

Objectives

By the end of this lab, students should be able to

• report lab data correctly based on the precision of the equipment used
• calculate density from data and report it with the correct significant figures

Chemistry Topics

This lab supports students’ understanding of

• significant figures
• density
• measurement
• accuracy
• precision

Time

Teacher Preparation: 45 minutes

Lesson: 45 – 60 minutes

Materials

• Lead Shot, 30 g per lab group (can be reused when dry)
• Large Lead Ball, hooked and tied to a piece of string
• Aluminum Shot, 10 g per lab group (can be reused when dry)
• Aluminum Density Block
• Copper Shot, 25 g per lab group (can be reused when dry)
• Copper Strip (1.2 cm x 15 cm)
• 10 mL Graduated Cylinder, 2, marked at 0.1 mL
• 25 mL Graduated Cylinder, marked at 1 mL
• 50 mL Graduated Cylinder, marked at 1 mL
• 1000mL Beaker, plastic suggested, marked at 100 mL
• Electronic Balance, 1 g, 2
• Electronic Balance, 0.01 g, 3
• Electronic Balance, 0.001g, 1
• Ruler with centimeter with millimeter markings, 2
• Weighing Boats, 3
• Thermostat, °F
• Electric Temperature Probe, 0.1°C
• Thermometer, 1° C markings
• Forceps

Safety

• Always wear safety goggles when handling chemicals in the lab.
• Students should wash their hands thoroughly before leaving the lab.
• When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.
• Follow the teacher’s instructions for cleanup of materials and disposal of chemicals.

Teacher Notes

This lab is set up in seven stations:

 Station Equipment Notes on Data Precision 1 lead shot (30 grams per lab group), weighing boat, electronic balance that reports to the 0.01 g, 10 mL beaker marked at 0.1 mL, water, paper towels Mass reported to 0.01 g Volume reported to 0.01 mL 2 large lead ball (hooked with string attached), electronic balance that reports to the 1 g, 1000 mL plastic beaker marked at 100 mL, water, paper towels Mass reported to 1 g Volume reported to 10 mL 3 aluminum shot (10 grams per lab group), weighing boat, electronic balance that reports to the 0.01 g, 25 mL graduated cylinder marked at 1 g, water, paper towels Mass reported to 0.01 g Volume reported to 0.1 mL 4 aluminum density block, electronic balance that reports to the 1 g, metric ruler marked to the millimeter Mass reported to 1 g Length reported to 0.01 cm 5 copper shot (25 grams per lab group), weighing boat, electronic balance that reports to the 0.001 g, 10 mL beaker marked at 0.1 g, water, paper towels Mass reported to 0.001 g Volume reported to 0.01 mL 6 copper strip, electronic balance that reports to the 0.01 g, 50 mL graduated cylinder marked at 1 g, water, forceps, paper towels Mass reported to 0.01 g Volume reported to 0.1 mL 7 classroom thermostat (°F), electronic temperature probe the reports to the 0.1°C, thermometer that reports to the 1°C Precision will vary depending upon your equipment
• If you have small strainers students can use them to drain the metal shot from water.
• Students should have already learned about using the Significant Figure rules.
• Students should also know how to calculate density and percent error.
• Discuss the importance of reading the meniscus at eye level when collecting liquid volume data.
• Before beginning the lab you should discuss how to use the equipment markings to report lab data.
• Equipment with marking intervals of 100: Readings can be estimated to the tens (10) place.
• Equipment with marking intervals of 10: Readings can be estimated to the ones (1) place.
• Equipment with marking intervals of 1: Readings can be estimated to the tenths (0.1) place.
• Equipment with marking intervals of 0.1: Readings can be estimated to the hundredths (0.01) place.
• For electronic equipment: The last digit is the estimated unit.

For the Student

Lesson

The purpose of this activity is to collect lab measurements that will allow you to calculate the density of three different metals. Calculated density values will then be compared to accepted values to find the percent error.Accepted density of each is shown in the table on the right.All lab measurements should be recorded to reflect the precision of the equipment used.

 Metal Density Aluminum 2.70 g/cm3 Copper 8.92 g/ cm3 Lead 11.34 g/ cm3

Directions and Data: Visit each station and collect the data needed to calculate the density of the metal.Record your data using the correct number of significant figures:

• Equipment with marking intervals of 100: Readings can be estimated to the tens (10) place.
• Equipment with marking intervals of 10: Readings can be estimated to the ones (1) place.
• Equipment with marking intervals of 1: Readings can be estimated to the tenths (0.1) place.
• Equipment with marking intervals of 0.1: Readings can be estimated to the hundredths (0.01) place.
• For electronic equipment: The last digit is the estimated unit.

Record your data with the correct number of significant figures.Check markings on your equipment and determine how to record the data before you begin.

When recording liquid volume data, be sure that you are reading the meniscus at eye level.

 Basic Rules for Significant Figures All the numbers that are not zeroes are significant: 89.6 has 3 significant figures 101.13 has 5 significant figures Zeroes between non-zero numbers are significant: 205.8 has 4 significant figures 5000.05 has 6 significant figures Leading Zeroes are not significant.They are place holders: 0.0073 has 2 significant figures 0.000000163 has 3 significant figures Ending Zeroes after a decimal point are significant. 49.00000 has 7 significant figures 9.0000 has 5 significant figures Ending Zeroes without a decimal are not significant, they are place holders. 2600 has 2 significant figures 999,000,000 has 3 significant figures

Data Table

 Lead Shot: Add ≈30 grams of lead shot to weighing boat.Use water displacement to measure volume. Initial Mass (g) Initial Volume (mL) Final Mass (g) Final Volume (mL) Pour water into sink and place wet lead on a paper towel to dry. Lead Ball: Use water displacement to measure volume. Mass (g) Initial Volume (mL) Final Volume (mL) Remove lead from water.Dry with paper towel.Leave water in beaker. Aluminum Shot: Add ≈10 grams of aluminum shot weighing boat.Use water displacement to measure volume. Initial Mass (g) Initial Volume (mL) Final Mass (g) Final Volume (mL) Pour water into sink and place wet aluminum on a paper towel to dry. Aluminum Block: Measure all three sides of the block using the metric ruler Mass (g) Side 2 (cm) Side 1 (cm) Side 3 (cm) Be sure to leave the station the same way you found it. Copper Shot: Add ≈25 grams of copper shot to weighing boat.Use water displacement to measure volume. Initial Volume (mL) Initial Mass (g) Final Volume (mL) Final Mass (g) Pour water into beaker. Place wet copper on paper towel to dry. Copper Strip: Record length and width of copper strip using the metric ruler. Use water displacement to measure volume. Mass Copper (g) Initial Volume (mL) Length (cm) Final Volume (mL) Width (cm) Use forceps remove strip. Dry with paper towel.Leave water in GC. Temperature: Record room temperature using the thermostat, temperature probe, and thermometer. Thermostat (°F) Thermometer (°C) Temperature Probe (°C)

Density Calculations: Calculate the mass, volume, and density of each substance. Show your work. Apply Significant Figure Rules to your calculations.

 Mass (g) Volume (cm3) Density (g/cm3) Lead Shot Lead Ball Al Shot Al Block Copper Shot Copper Strip

Temperature Conversions:

 Thermostat: Convert to °C and K Temperature Probe: Convert to °F and K Thermometer: Convert to °F and K

More Questions: Show all work. Apply Significant Figure Rules to calculations.

 Calculate the average temperature of the room using your three Kelvin values. Calculate the Percent Error value using the accepted values from page 1. 10 x | Accepted – Actual | Accepted Lead Shot Aluminum Shot Copper Strip Use the length, width, and volume of the copper strip to calculate the thickness in MILLIMETERS. Which station allowed you to calculate a more precise value for density?Explain why. Which station allowed you to calculate the least precise value for density?Explain why.