MYSTERY POWDERS END OF UNIT ASSESSMENT
The Mystery Powders End of Unit Assessment is scored on the basis of student responses
recorded on the last page of the test booklet. Look at the results and conclusion page of the
test booklet. Notice that students are asked to record three things: (1) What's inside?, (2)
What test(s) told you?, and (3) How did you know?/What happened?
Students receive points for: (a) correctly identifying the Mystery Powder, and (b) providing
evidence to support their answer. Evidence is provided by naming the tests they used (e.g.,
water) together with the observations they made
(e.g., doesn't dissolve). Their score is based on the quality of the evidence they provide.
There is a unique combination of tests and observations which provide the evidence needed to
identify each of the Mystery Powders. When there are two substances in the Mystery Powder
mixture students need to provide confirming evidence for each substance or a combination of
confirming and disconfirming evidence. When there is only one substance in the Mystery
Powder, students need to provide confirming and disconfirming evidence. In other words,
students need to rule in the substance that is present, and rule out all other substances which
are paired with the known substance in one of the other Mystery Powder mixtures.
STEPS IN SCORING
Turn to the last page of the student's test booklet.
FOR EACH MYSTERY POWDER record the following on the score form:
1. CORRECT ANSWER
(What's Inside the Bag?)
• Correct: Put a 1 in the box to the left of the name(s) of the substances contained in the
Mystery Powder if the student's response is correct. If there are two substances in the
mixture, students must correctly identify both to receive 1 point.
• Incorrect: Put a 0 in the box if the student's answer is incorrect. Record student's
incorrect answer in the space below the name of the Mystery Powder.
• Add together the scores for all the Mystery Powders. Record the "Total Correct
Answers" in the box at the lower left of the score form.
(What test(s) told you? and How did you know? /What happened?)
The score, to be recorded in the box on the extreme right side of the score form, is based
on the quality of evidence the student provides.
• Mark the oval to the right of the test (iodine, vinegar, water, touch, sight, taste)
to indicate the test reported by the student.
• Mark the oval next to the observations the student made (e.g., salty, like salt).
Sometimes the student's observations are worded differently than those on the
score form (e.g., student writes rough instead of grainy). Write down the student's
response on the score form.
• Various combinations of tests and observations provide more or less adequate
evidence to support the identification of a Mystery Powder. Turn to the next page for
QUALITY OF EVIDENCE EXAMPLE
Complete Evidence--4 Points
All black and white
observations and corresponding 1 4
tests are reported.
Strong Evidence--3 Points
One black OR all white AND
one or more underlined 1 3
observations and corresponding
tests are reported. 1 3
Partial Evidence--2 Points
One black OR all white
observations and corresponding 1 2
tests are reported.
Weak Evidence--1 Point
One white AND/OR one or more
underlined observations and 0 1
corresponding tests are reported. only
Inadequate Evidence--0 Points
No relevant tests and observations
are reported OR tests are reported
without corresponding only
• Refer to the examples on the previous page and "Quality of Evidence" box at
the bottom of the score form to determine the score for each Mystery Powder.
Record a score in the box on the extreme right side of the score form. If the
student's words do not match what is on the score form but mean the same thing,
then give the student credit.
If there are one or more observations marked without corresponding
tests then subtract one half point from the score. Subtract a maximum
of 1/2 point even if the student reports several observations without
1 4 3.5
1 4 3.5
• Add together the score for each Mystery Powder and record the "Total
Quality of Evidence" score in the box at the lower right of the score form.
3. When you have completed the scoring for all students, see the instructions for score
summary and interpretation.