Lab 2.3 Measuring the Densities of Irregular Objects
Guiding Question: How can we find the density of oddly shaped objects?
You will use the water displacement method to measure volume. Volume is a measure of the amount of space an object takes up. When an object is submerged in water, it pushes water out of the way. If you measure the amount the water level increases, that is equal to the volume of the object. An object displaces water equal to its volume.
Look at the illustrations below showing the water level in a graduated cylinder before and after a sample is submerged in water. What does this difference in water level tell you about the object?
With the illustrations, use water displacement to find the volume of each object. Record the initial and final water level and report the volume of each object in the boxes provided.
A graduated cylinder measures volume in milliliters (ml). When you use a ruler to measure volume, you report cm3. 1 ml = 1 cm3
1. Chose 2 objects. Each student will complete their own lab sheet. You choose one of the minerals plus one more out of the objects available:
Minerals – different ones, you will use the density to identify the mineral
a. Measure the mass of the object in grams and record.
b. Put enough water in cylinder to cover object.
c. Record the volume of water in ml.
d. Carefully place the object in cylinder so water is not splashed out of or onto the sides of the graduated cylinder. Record new water level.
e. Calculate the volume of the object by subtracting the initial volume from the final volume. Record the volume of the object in ml. See example above.
f. Calculate the density of the object. Record in grams/ml
3. Create a data table. Think carefully about the measurements you will make during the procedure. Make sure you have a place to record each measurement and calculation in your data table. Label the rows and columns.
4. Analysis Questions: Please answer in a complete and meaningful sentence
a. Answer the guiding question.
b. Describe water displacement in your own words.
c. Based on the density and other physical properties you can observe listed on the mineral data table, identify the mineral.
d. What parts of the procedure or equipment would you have to change if you wanted to find the density of a person?
Resources: ACS Middle School Chemistry, Chapter 3, Lesson 2 www.mrlucas.com/Page%20Files/volume%20by%20displacement.pdf