Do the lab and fill out the document labeled “lab document” attached below, use the other document labeled exercise 2 attached for additional info.
In this exercise, you will identify three unknown substances by using the data I gathered in Exercise 2. (attached below)
PROCEDURE
- Locate the three unknown samples and examine them closely.
Note: You have already developed a set of hypotheses in Exercise 2, question 4. Refer to these hypotheses as needed.
- Design an experiment to determine the identity of the unknowns using at least 3 methods of identification. Record the steps that you will take in Panel 1: Experimental Methods.
- Determine the appearance, scent, mass(g), behavior in water and behavior in vinegar for unknowns 1–3.
- Record all data in Data Table 7.
- Based on the data you collected, draw a conclusion about the identity of each substance.
Note: Refer back to the data you collected in Data Tables 2–6 to help in your identification of the unknowns.
- Record your conclusions in Data Table 7.
Lab: Data collection
PROCEDURE
- Select baby powder, baking soda, corn starch, powdered sugar, and zinc oxide. Set the
other samples aside for later use.
Note: Zinc oxide is a common ingredient in some sunscreens, diaper ointments and makeup. - Review Data Table 2–6 which list a series of tests that will be applied later in the
experiment to identify unknown substances.
TEST FOR APPEARANCE: - With scissors and a ruler, cut a 10 x 10 cm piece of paper. Label the paper “baby
powder.” - Open the vial containing baby powder. Transfer all of the contents of the vial to the
labeled piece of paper. - Describe the appearance of the baby powder and record your observations in Data Table
2.
Note: Close visual observation may offer subtle differences among the samples. - Repeat steps 4–6 for each of the substances in the remaining 4 vials (baking soda, corn
starch, powdered sugar, and zinc oxide). Be sure to label each piece of paper
appropriately.
TEST FOR SCENT: - Test the scent of the baby powder by using your hand to gently waft the odors toward
your nose. Record observed scent in Data Table 3.
Note: Do not directly inhale any of the substances. Waft the odors toward your nose using a
circular motion with your hand at a distance of 6-8 inches. - Repeat step 8 for the four remaining substances.
TEST FOR MASS (G): - Locate a digital scale. Turn on the scale, and set the scale to grams.
- Using scissors cut a piece of paper that is about 5 x 5 cm2, just big enough to cover the
scale. This will be your weigh paper. - Using scissors cut a piece of paper that is about 10 x 10 cm and label it Baby Powder.
This will be the paper you use to pour out the baby powder onto. - Place the piece of paper on the scale. Notice that the mass of the paper in grams is
displayed. - Press the power button once to tare the scale to read 0.00 g.
Note: The scale will read 0.00 g with the piece of paper on top. The scale is set to automatically
turn off after some time. If this occurs, simply press the power button to turn the scale back on.
The scale will again read zero. - Locate a kitchen knife and a ¼-teaspoon.
- Pour the contents of the vial that contains the baby powder onto the 10 x 10 cm2.
- Use the knife and measuring spoon to collect a heaping spoonful of baby powder from
the 10 x 10 cm paper. - Scrape the excess powder from the spoon and back onto the paper labeled baby powder.
The sample of baby powder should be perfectly even with the top of the spoon, as shown
in Figure 2. - Reserve the excess baby powder for future steps.
Figure 2.
Measuring a solid. A. Creating a heaping teaspoon. B. Scraping off excess powder. C. Final,
level measure. - Ensure that the scale is still on, and gently transfer the baby powder from the measuring
spoon to the center of the paper on the scale. Be careful not to spill any powder, as this
would result in experimental error. Gently tap the spoon on the paper so that all of the
contents are transferred. - Record the mass of the baby powder in grams in Data Table 4.
- Locate a test tube and a marking pen. Label the test tube BP. It will contain the ¼ tsp
baby powder and be used in later steps. - Gently fold together two opposite corners of the weigh paper containing baby powder.
Use the paper as a funnel to slowly and carefully add the baby powder to the test tube.
See Figure 3.
Figure 3.
Using weigh paper to add solid to a test tube. - Locate a 24 well plate in your kit. Set the well plate on a solid surface and place the test
tube in the well plate. - Dispose of the weigh paper in a trash bin, as it may hold some residual powder and thus
cannot be reused for the other substances. - Rinse the measuring spoon and knife with copious amounts of tap water and dry
thoroughly with a paper towel. - Repeat steps 10–26 for the four remaining substances. Be sure to create new 5 x 5 cm2
weigh paper and 10 x 10 cm2 paper, and properly clean the equipment between testing
each sample.
TEST FOR BEHAVIOR IN WATER: - Gather a 1-teaspoon and the funnel provided in the kit.
- Securely hold the funnel and test tube containing the substance in one hand. The funnel
opening should rest just at the lip of the test tube, as shown in Figure 4.
Figure 4.
Test tube and funnel. - While still holding the test tube and funnel, fill the 1-teaspoon to the brim with tap water.
- Add the water to the funnel and allow it to move into the test tube.
- Add a second teaspoon of tap water.
- Set the funnel and the measuring spoon aside.
- Place a gloved thumb over the opening of the test tube and vigorously shake the test tube
to completely mix the solid with the water. - Place the test tube back in the well plate and allow the solution to sit for 1 minute.
- Record observations for the behavior of baby powder in the presence of water in Data
Table 5.
Note: Be as specific as possible with your observations. Particles may dissolve, become
suspended, precipitate (settle to the bottom of the test tube), or display a combination of
behaviors. - Rinse the measuring spoon with copious amounts of tap water and dry well with paper
towels. - Repeat steps 29–37 for the four remaining substances.
TEST FOR BEHAVIOR IN VINEGAR: - Locate the bottle of vinegar and remove the cap. Add 10 drops of vinegar to a clean well
in the 24 well plate. - Use a toothpick to scoop up a small amount of baby powder, as shown in Figure 5.
Figure 5.
Toothpick and baby powder. A. Scooping baby powder with toothpick. B. Transferring powder to
24 well plate. - Add the baby powder to the well containing the vinegar and observe immediately.
- Record observations for the behavior of baby powder in the presence of vinegar in Data
Table 6. - Repeat steps 40–42 for the four remaining substances.
Answers
Data table 2: Appearance
Baby powder Baking soda Corn starch Powdered sugar Zinc oxide
It is Fine, Light
White Dust
It is Fine and
White in color
The powder was
white fines and
contained a
yellow particles.
The powder had
grains and was
white
It is non-uniform
white powder,
with some
metallic sheen
Data table 3: Scent
Baby powder Baking soda Corn starch Powdered sugar Zinc oxide
fresh /vanilla
scent
No scent Flour scent Sweet scent No scent
Data table 4: mass (g)
Baby powder Baking soda Corn starch Powdered sugar Zinc oxide
1.80 2.01 1.86 2.02 3.20
Data table 5: Behavior in water
Baby powder Baking soda Corn starch Powdered sugar Zinc oxide
Some particles
dissolve.
Other particles
suspended but
when shaking
stopped they
settled at the
bottom.
Cloudy White
Water solution
The Test tube
temperature
raised slightly.
The powder
began to fizz.
The powder
turned pasty.
The powder
displayed no
visible instant
changes.
After some time,
it had slightly
dissolved.
Undissolved
particles settled
at the bottom.
Cloudy White
Water solution.
Bubbling was
noticed.
Some zinc oxide
went to the
bottom some
went to the top.
Data table 6: Behavior in vinegar
Baby powder Baking soda Corn starch Powdered sugar Zinc oxide
Lots of bubbling
that ends
quickly
The powder
fizzed/Bubbling
No bubbles
The powder
turned pasty
The powder
displayed no
visible change
but it did
dissolve slightly.
Bubbling was
noticed.
Cloudy white
solution - A hypothesis for Exercise 2 might state, “If the five substances are distinct, then they will
have unique characteristics that distinguish them from one another.” Was this hypothesis
supported or disproved? Support with your answer with a 1-2 sentence explanation.
This hypothesis was supported. All the 4 substance had different characteristics even on their
appearance. The baby powder and baking powder was the only trick substance since their
characteristics appeared very close but after mixing them with either water or vinegar, baby
powder did not fizz in water unlike the baking powder. - Define quantitative data and qualitative data. Which variables in the experiment were
quantitative and which were qualitative?
The qualitative data was appearance, ascent, reaction with water and vinegar.
The quantitative data was mass. - List each substance and its distinguishing characteristics. (You do not have to list every
characteristic of each substance, just the characteristics that set each substance apart from the
others.)
· Baby powder; the powder only fizzed in vinegar but only showed suspended
particles which when shaking stopped they settled at the bottom
· Baking soda; the powder fizzed both in water and vinegar.
· Corn starch; the powder was white fines and contained a yellow particles.
· Powdered sugar; the powder had grains and was white.
· Zinc oxide; It is non-uniform white powder, with some metallic sheen - In Exercise 3, you will identify three unknown substances. Using the characteristics from
the previous question, create a set of hypotheses that may be applied to each unknown.
(Hint: Phrase the hypothesis as an “if-then” statement. For example, “If the unknown substance is
an insoluble white powder that has no scent, then the substance is X.”)
vIf the unknown substance is an insoluble in water, white powder that has
vanilla scent, and fizzed in vinegar, then the substance is baby powder.
If the unknown substance is soluble in either water or vinegar, white powder
that has no scent, and fizzed in both solution, then the substance is baking
soda.
“If the unknown substance is an insoluble powder with white fines and
contained a yellow particles that has no scent and it is pasty when mixed with
either water or vinegar, then the substance is starch corn.
If the unknown substance is soluble in either water or vinegar, grainy white
powder that has no scent, then the substance is powdered sugar powder.
If the unknown substance is fizzing in either water or vinegar, non-uniform
white powder with some metallic sheen and that has no scent, then the
substance is zinc oxide.
Panel 1: Experimental Methods
Data Table 7: Experimental Data and Conclusions
Unknown # Appearance Scent Mass (g) Behavior
in water
Behavior in
vinegar
Conclusion
1
2
3
- What were the three unknown substances? What characteristics do the three
substances have in common? What characteristics set the three substances
apart? - Was it necessary to apply every test to each of the unknowns? Why or why not?
- List an additional test that might have been useful in Exercises 2 and 3.
- Summarize how you used the steps in the scientific method to identify the
unknowns.
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