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Hydrated Salt
Task with Student Directions

Grades 9-12 Performance Task
Contributed by: New York State Education Department (NYSED)
Developed through University of Buffalo and NORC (1991)

Part A

Introduction:

This laboratory test presents a problem. Your task in Part A is to plan and design an experiment to solve the problem. You will have 30 minutes to complete Part A. At the end of the 30 minutes, your answer sheet will be collected. You will then receive separate directions for Part B. In Part B you will use materials and equipment provided in the laboratory kit to collect experimental data for this problem. You may wish to do your preliminary planning on the sheet labelled "Working Copy." Write this plan on the appropriate answer sheet in your test booklet.

Problem:

A hydrated salt is a solid substance with water molecules at some of the lattice points in the crystal. The formula of a hydrated salt is written in a form that includes the number of water molecules associated with it. This water can be driven out of the crystal by heating. Your task is to design an experiment, using the materials (and/or others) listed below, which will determine an empirical formula for a hydrated salt X. Be sure to tell how you know when all the water has been removed from the hydrate crystals.

a) Under the heading PROCEDURE list in order the steps of the procedure you will use to solve the problem. You may include a diagram to help illustrate your plans for the experiment. Include any safety procedures you would follow.

b) Construct a DATA TABLE or indicate any other method that you could use to record the observations and results that will be obtained.

PLEASE NOTE: In Part A you are NOT to proceed with any part of the actual experiment. You are just to plan and organize a way to investigate the problem.

Materials:

  • 1 crucible with cover
  • 1 pair of crucible tongs
  • 1 porcelain triangle
  • 1 tripod
  • balance
  • bunsen burner with matches
  • heat resistant tile
  • hydrated sample X
  • access to a periodic table
  • safety goggles
  • calculator

 

ANSWER SHEET

PART A - Experiment Design

Organize your experiment design under the following headings:
PROCEDURE and DATA TABLE.
Use the front and back of these sheets if necessary.

PROCEDURE (Include diagram if appropriate)

 

 

 

DATA TABLE (For results and observations)

 

 

 

Hydrated Salt - PART B

Determination of the formula of a hydrated salt

You will have 50 minutes to complete this part. You have been provided with a detailed Procedure (see next page) which you are to follow. Record your work for Part B on the answer sheet under the appropriate headings.

a) Perform the experiment by following the steps outlined in the procedure.

b) Under the heading RESULTS/OBSERVATIONS record the results of the experiment. Use statements, descriptive paragraphs, and tables of data where appropriate.

c) Under the heading CALCULATIONS show all equations and calculations used.

d) Under the heading CONCLUSION give an interpretation of your results. What did you learn from the experiment?

e) You have also been provided with a sheet labelled "Working Copy." Use this scrap sheet for any initial calculations or conclusion. However, be sure to enter your final work on the appropriate answer sheets.

f) At the end of the 50 minutes, your answer sheets will be collected.

Materials:

  • 1 crucible with cover
  • 1 pair of crucible tongs
  • 1 porcelain triangle
  • 1 tripod
  • balance
  • bunsen burner with matches
  • heat resistant tile
  • hydrated sample X
  • access to a periodic table
  • safety goggles
  • calculator

Procedure:

  1. Determine the mass of a clean dry crucible and cover. Record the data in the data table.

  2. Place about 4 grams of sample X in the crucible.
  5. Weigh the crucible, lid and hydrated sample. Record this data in the data table.

  6. Set up the apparatus as shown in the diagram on the previous page.

  7. Heat te crucible gently at first and then more strongly. Continue heating for about 5 minutes, and no more than 8 minutes.

  8. Stop heating and weigh the crucible, lid and solid left. Record the data in the data table.

  9. Given your data, determine the empirical formula of hydrated salt X, of the form: X * ________ H20

Safety:

The hydrate crystals pose no acute toxicity or corrosivity hazard. However:

(1) Safety goggles must be worn at all times.

(2) Hot objects must be handled with tongs at all times.

(3) Should skin contact occur, flush thoroughly with water.

 

EXPERIMENT REPORT #5 - Part B

Record your Calculations and Conclusions on these sheets.

RESULTS/OBSERVATIONS

 

 

CALCULATIONS

 

 

CONCLUSION

 

 

 

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