Determining the Density of Objects
Why does wood float and iron sink? Wood floats because it has a lower density than water. One of the factors (not the only one) that will determine if something floats or sinks is density. Density is the amount of matter per amount of space the object occupies. In this activity you will experimentally determine the density of substances composed of different materials.
Problem: How to determine if an object would float on water?
Variables:
Hypothesis:
Materials: Density cube set, Ruler, Balance, Cup, Mystery cylinder, Water, Alcohol or Oil, Dropper
Pipette, Graduated cylinder,
Procedure:
PART A (Record results in the observations section)
1.
Place the graduated cylinder on the balance and press the Zero/tare button.
2.
Place about 2.0 ml of water into the graduated cylinder and record the mass and volume.
3.
Add about 1 more ml to the graduated cylinder (total 3ml) and record the mass and volume.
4.
Continue adding about 10 ml at a time (recording the mass & volume each time) until you have 5 samples.
5.
Calculate the density of water.
6.
Empty and dry the graduated cylinder.
7.
Take a new graduated cylinder and repeat steps 1-4 using the rubbing alcohol. (Oil may be used instead)
8.
Calculate the density of the rubbing alcohol.
9.
Using the dropper pipette, carefully drip each about 20 ml (2 finger widths) of each liquid into the test tube so that the liquids DO NOT switch places. Tilt the test tube and let the liquid run down the inside of the test tube. Drop slowly.
10.
Diagram the test tube when completed.
PART B (Record results in the observations section)
11.
Pick up each cube and predict and record if it will float or sink.
12.
Calculate and record the volume for each cube. YOU MUST MEASURE THE LENGTH, WIDTH
AND HEIGHT OF EACH CUBE. Some cubes have the same volume, some do not!
13.
Press the Zero/ tare button (once) and record the mass for each cube.
14.
Calculate the density for each cube.
15.
Predict AND record whether each cube will float again.
16.
Place each cube in water and record your observations. Please remove and dry cube as soon as possible.
Part C (Record results in the observations section)
17.
Calculate the density of the mystery cylinder. Formula= Mass /  r 2 x h

Observations:
PART A
1
Mass
2
Volume
3 4 5 Averag e
Densit y
Mass
1 2 3 4 5 Averag e
Densit y
Volume
Diagram: (step # 10)

PART B
Material Characteristics Mass Volume Density Prediction
(step 11)
Copper Copper Cube
Brass Gold Cube
Steel Black Cube
Aluminu m
Silver Cube
Acrylic Clear Cube
Oak Dark Thin
Grained
Nylon Opaque White
Pine Yellow Thick
Grain
Poplar Thick grained
PVC Dark Grey
Prediction
(step 15)
Result
(step 16)
PART C
Density of Mystery Cylinder:

ANALYSIS
Part A
Create one graph to represent the data obtained in part A. Make sure to include all appropriate labels and a title.
Part B
Material
Copper
Density Accepted Value % Error
Brass
Steel
Aluminum
Acrylic
Oak
Nylon
Pine
Poplar
PVC
Water
Alcohol
Conclusions:
1.
Write a conclusion to this experiment. (Answer the problem, was your hypothesis supported, provide several pieces of data to support your conclusion)
2.
Were there any changes in your prediction in step #15 from your prediction in step #11?
If yes list which ones.
3.
According to your calculations which of the following cubes would float in water and explain why?
4.
According to your data what is the composition of the mystery cylinder. Explain your answer.

5.
Describe how you would measure the volume of an irregular shaped object such as a rock?
6.
List possible sources of experimental error in this experiment(s). (Reasons for why you have % error.)
7.
Five objects below were placed into a container of water.
Pancake syrup = 2.0 g/ml,
Isopropyl alcohol = .5 g/ml,
Water = 1.0 g/ml,
Rubber ball = 3.0 g/ml,
Plastic Cube = .9 g/ml.
Create a diagram to show the relative positions of each object in the water.