Investigation 2: Archimedes Principle

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In this experiment you will be measuring the mass and volume of various objects and using these measurements to calculate densities and make predictions. The investigation is designed to give you an understanding of:

  • Density
  • Buoyancy and Archimedes principle
  • Uncertainties



You may either do this investigation alone or with up to one other person currently enrolled in the course (ie. you may not work as a group of three or more). If you work with someone else you need to acknowledge your collaborator (include their name and student number in the report). In this case you must answer the questions individually even if your data is the same. If you have identical answers that will be considered plagiarism, so while it is OK to collect the data together you need to answer the questions and plot the graphs etc. as individuals.



Assemble this equipment before you start the exercise:

  • A measuring jug
  • A small bottle with a lid (you need to be able to completely submerge it in the measuring jug), a traveling shampoo bottle may be appropriate. You may find it easier to use a larger bucket for parts of the experiment.
  • A camera
  • Cooking salt (a few tablespoons)
  • Sand (or you could use even more cooking salt)
  • Scales (that can measure mass)


Risk Assessment

Read over the experimental method and then complete a risk assessment in the table below. You must minimize all risks before you start. Add as many rows to the table as you need. If any of the risks rank above medium then you need to adapt the experiment to make it safer before proceeding.



(Step 3)

Associated risks

(Step 4)

Existing risk controls
Risk rating with existing controls *

(Step 5)










By proceeding with the experiment you are agreeing to follow these risk control methods and conduct the experiment safely. If you have any doubts about your ability to complete the experiment safely then you should not proceed. In your report you need to state that you agree to follow these risk controls. Without this statement your report will not be marked.


  1. Record the mass of the empty (dry) bottle (with an uncertainty).
  2. Completely submerge the bottle in the water and record how the volume changes. Do not put your finger under the water, just the bottle. Putting your finger under the water will displace extra water and change your results. Use this to calculate the volume of your small bottle. Include an uncertainty in this result.
  3. Place the measuring jug (containing water) on the scales. Record the mass change in the jug (with uncertainty) when you completely submerge the small bottle in the water.
  4. Take a photo showing what happens when empty bottle is placed in the jug.
  5. Completely fill the bottle with sand or salt. Place it in the measuring jug filled with water. Draw diagram or take a photo showing what happened to the jug. Record the mass of the sand in the bottle with an uncertainty.
  6. Predict the maximum mass of sand/salt you can have in the bottle while the buoyancy force is to equal the weight force.
  7. Measure what maximum mass of sand you can have in order to have the weight force and buoyancy force equal. Take a photo that clearly (ie. from side on, not from on top of the jug) shows that these two force are equal. Leave the salt/sand in the bottle for the next part.
  8. Describe a method you could use to make a saturated salt solution and measure its density. Follow this method. Predict what will happen when you place the bottle with the sand/salt from step 7 into this solution. Be precise and include reasons. Observe what happens. Include a sketch or a photo.


Results and Analysis:


Step 1

Mass of bottle:


Step 2

Initial volume reading:

Final volume reading:

Volume of small bottle:


Step 3

Initial mass of jug:

Final mass of jug:

Change in mass when bottle submerged:


Step 4

Image of empty bottle in jug


Step 5

Image of filled bottle in jug

Mass of bottle and sand/salt:

Mass of sand/salt:

Step 6

Predicted mass of salt/sand in the bottle:


Step 7


Mass of bottle and sand/salt:

Mass of sand/salt:


Step 8


Density of salty water:





  1. Explain your result in step 3 of the experiment. Include a diagram showing the forces that are acting in this case.
  2. Explain observation in step 4.
  3. Explain the observation in step 5.
  4. Was the mass you predicted in step 6 equal to the mass you measured in step 7? Give a detailed explanation of why or why not.


What to submit:

Submit a report through TurnItIn on Moodle. The report should include:

  • A statement of the aim of the investigation
  • A statement saying that you will follow the risk controls recommended in the risk assessment
  • Everything in the results and analysis section of the investigation
  • Details of your analysis of the results and predictions (ie, show how you did the calculations)
  • Answers to the questions
  • A conclusion stating what you have found out


You report should not include:

  • The procedure (as this has been given to you, only comment if you make a change to this procedure)


You may write your report neatly by hand and scan it in (there are apps for iphones and ipads that allow you to scan documents in, this is much easier for your tutor to read than a photo) or type-set it. It can take a long time to typeset mathematical expressions so the first option may be a lot faster. If your report is predominantly handwritten please attach a cover sheet to it so that it gets processed through TurnItIn. If you include handwritten material it needs to be neat and easy to read. If your tutor can not easily read it they will not mark it. The report needs to be in a single file. It is better to submit a .pdf than a word document as word documents can look different on different computers. Your tutor will mark the report as it is displayed on their machine.



Rubric (this rubric has been programmed into TurnItIn):


Criteria Maximum possible marks
Identified at least two tasks with hazards, associated risks and suitable controls identified. Rated these risks and controls using codes in “Rating Risks” document 2
Measured volume of bottle with suitable uncertainty 1
Measured mass change of jug when bottle is submerged including an uncertainty 1
Shown (photo) what happens when an empty and full bottle is placed in jug of water 1
Recorded mass of sand in bottle with uncertainty 1
Used results to predict (correctly for measured values) the mass of sand/salt needed in the bottle. 1
Photo clearly shows bottle in equilibrium 1
Suitable method for creating a saturated salt solution and measuring its density 1
Predicted what will happen to bottle when placed in saturated salt solution, observed it. 1
Answered question 1 1
Answered question 2 1
Answered question 3 1
Answered question 4 1
All values in report stated with appropriate units 1



TOTAL: 15 (This contributes 5% towards your total mark for the subject)

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