Experiment 2: Density
Chem 310
Sep 07 – Sep 11, 2021
In General: Where/How to start?
Step 1: read the introduction of the lab
To understand what this lab is about
To connect the lab material with the lecture material
Help to answer conceptual questions
Step 2: read the report sheet
To have an idea of what the instructor asking you
Step 3: read the experimental procedure
This is the most important step
This procedure is a step by step instruction on how to answer the questions in the report sheet
Experiment 2: Density
Step 1: read the introduction
It’s about chemical properties and physical properties
It’s about density
Density is a physical property
The difference in densities of pre-1983 and post-1983 pennies
Step 2: read the report sheet
Asked to find mass and volume of pre-1982 pennies
Asked to find mass, volume, and density of post -1983 pennies
Answer to conceptual question 1 & 2
Asked to work on density problems
Step 3: read the experimental procedure
This procedure is a step by step instruction on how to answer the questions in the report sheet
Experiment 2: Density
Part 1: Pre-1982 pennies
Look at pictures in the experimental procedure to determine mass of beaker and mass of 100 pennies and beaker.
Mass of 100 pennies = (mass of 100 pennies + beaker) – mass of beaker
Volume of 100 pennies = mass of 100 pennies / density of Cu
Since pre-1982 pennies are made mainly with Cu (over 95%)
Volume of 10 pennies can be extrapolated from volume of 100 pennies
Volume of 10 pennies = Volume of 100 pennies / 10
Volume of 1 pennies can also be extrapolated from volume of 100 pennies
Experiment 2: Density
Part 1: Pre-1982 pennies
Look at your experiment 1 to find the average volume of 1 penny using geometry and displacement method.
Remember to convert all values of volume to mL
Accuracy and Precision in the lecture slides of Chapter 2
Experiment 2: Density
Part 2: Post-1983 pennies
Look at pictures in the experimental procedure to determine mass of beaker and mass of 100 pennies and beaker.
Mass of 100 pennies = (mass of 100 pennies + beaker) – mass of beaker
Volume of 100 pennies in part 1d = Volume of 100 pre-1982 pennies
The one that you determined using density of Cu and mass of 100 pre-1982 pennies
The assumption that volume of pre-1982 and post – 1983 pennies are similar is made here
Density of 100 post -1983 pennies= mass of 100 post 1983 pennies / volume of 100 pennies
Experiment 2: Density
Conceptual question 1 and 2
Why do we need to weigh 100 pennies rather than just one?
In your own word and thinking
Can relate to the lecture note to answer this question
Experiment 2: Density
Conceptual question 1 and 2
After comparing the volume of a penny among three different techniques of experiment 1 and 2. In your opinion which method is the most precise and why?
In your own word and thinking
Can relate to the lecture note to answer this question
Compare the values of the three methods here
Experiment 2: Density
Density Problems:
Using the main equation:
Density = mass / volume
Other derived equations:
Mass = density x volume
Volume = mass / density
Experiment 2: Density
Deadline:
Please submit your lab on canvas by 11:59 pm Saturday Sep. 11, 2021.
Good luck!
Email me if you have questions or zoom with me.
