Identifying Four Unknown Powder Substances

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Identifying Four Unknown Powder Substances

I. ABSTRACT

In the experiment, there were four different unknown powder substances and three liquids (water, iodine, and vinegar) used to mix with them to determine their identity. The experiment determined that Powder A was corn starch because of the chemical indication of iodine turning purple. Powder B was salt because of its physical characteristics. Powder C was baking powder because of its color change to iodine and its chemical reaction with the alkalinity of iodine and water due to the mix of corn starch it contained. It was also concluded to be baking powder because of its chemical reaction to the acidity of the vinegar due to the mixture of baking soda it contained. Powder D was concluded to be baking soda because of the similarity of the chemical reaction that happened between vinegar and the mix of baking soda in Powder C.

II. INTRODUCTION

The purpose of the experiment is to determine the relationship(s) between unknown substances and their reactions with the following liquids: iodine, vinegar and water. Their identities and properties were determined based on the observations from the chemical reactions.

III. EXPERIMENTAL

There were four unknown substances, and three known liquids: iodine, vinegar and water. Iodine is a chemical indicator for starch and will turn purple if it is present in the substance (1) while vinegar is a common household liquid used for cooking. The materials that were used in the experiment were simple tools and substances that can be found in a common and basic lab. The liquids used during the experiment were stored in three different beakers. A 4X6 well tray was used to display and make the comparison between the different substances after being tested with each of the three liquids. The 4X6 well tray labeled rows as A, B, C, and D, while the columns were labeled as 1, 2, 3, 4, 5, and 6. Wooden sticks were used to measure the amount of powder that was placed in each well. Plastic pipettes and an iodine dropper were used to measure the amount of liquid that was added to the powders. Toothpicks were used to mix the powders and the liquids. The procedures conducted for the experiment are as followed:

1. Each beaker containing one of the liquids was labeled; one beaker contained water, another iodine, and the last one contained vinegar.

2. Each one of the unknown powders was labeled with letters-- A, B,C, and D. One powder was A, another B, etc.

3. Each powder was given an assigned wood stick to prevent contamination.

4. Each liquid was given an assigned pipette to prevent contamination.

5. An observation of each powder's characteristics was recorded.

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6. With its clean, unused, wood stick, some of powder A was placed in row A of the wells tray into its four different columns of wells.

7. This process was repeated for all of the unknown powders into rows B, C, and D.

8. Once all of the powders had been placed in, the wells tray contained four rows, each row containing each powder and four columns of the row filled with that powder.

9. The iodine dropper was used to add ten drops of iodine to the second column of each row of powder.

10. The mixtures were mixed with four separate toothpicks.

11. Observations were recorded.

12. The toothpicks were disposed.

13. The water pipette was used to add ten drops of water to the third column of each row of powder.

14. The mixtures were mixed with four separate toothpicks.

15. Observations were recorded.

16. The toothpicks were disposed.

17. The vinegar pipette was used to add ten drops of vinegar to the fourth column of each row of powder.

18. The mixtures were mixed with four separate toothpicks.

19. Observations were recorded.

20. The toothpicks were disposed.

21. The first column was left alone.

When conducting this experiment, controls were utilized, including the control column on the wells tray that was used to compare the original state of the powder to the other states of the powder after being mixed with the different liquids. The amount of drops of each liquid per well was another control. The independent variable consisted of the three liquids, and the dependent variable included the reactions that occurred to the powder substances when each different kind of liquid was added.

3 IV. RESULTS AND ANALYSIS The Appearances of the Mixtures After Iodine Is Added to Column Two

The Appearances of the Mixtures After Water Is Added to Column Three

4 The Appearances of the Mixtures After Vinegar Is Added to Column Four

The Observations Taken of the Additions of Liquids to Unknown Solids

Observations of pure powder

Observations of powder mixed with

iodine

Observations of powder mixed

with water

Observation s of powder mixed with

vinegar

Powder A

The powder was fine and contained a yellow

tint.

The powder turned purple and pasty. After it was left alone for some time, it turned slightly pink.

The powder turned pasty.

The powder turned pasty.

Powder B

The powder had grains and was white.

The powder didn't change color but instead

maintained the same yellow color as the iodine.

After some time, the powder seemed to have dissolved only slightly.

The powder displayed no visible

instant changes. After some time, it

seemed to have slightly dissolved.

The powder displayed no visible change

but it did dissolve slightly.

Powder C The powder was fine

and white.

The powder began to fizz The powder began

and turned purple.

to fizz.

The powder fizzed more than usual.

Powder D The powder was a little The powder became pasty The powder turned

bit grainy and also

but stayed the same

pasty.

white.

yellow color as the iodine.

The powder fizzed.

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In the experiment, powders A and C strongly resembled each other, though powder A had a small tint of yellow. Powder B was the most diverse of all the powders because of its prominent grains. Powder D was less finely grounded than powders A and C but much less grainy than powder B. When ten drops of iodine were added to the powders, powder A turned purple which indicated that it contained starch; powder B only slightly dissolved but didn't react with the iodine. Powder C turned purple as well, meaning it contained starch, but it also fizzed, meaning it reacted to iodine as an acid due to iodine being a base (2). Powder D didn't show any chemical changes, having only formed a homogeneous mixture. When water was added to the unknown powders, powders A and D turned into a pasty homogeneous mixture. Powder B only slightly dissolved after some time had passed, and powder C fizzed once again, meaning that it reacted to the alkalinity of the water. When vinegar was added to the powders, powder A formed a pasty homogeneous mixture once more. Powder B, once again, only dissolved slightly with some time, and powders C and D fizzed with the vinegar which means they reacted to its acidity.

With the observations, it was determined that powder A is corn starch due to corn starch being slightly yellow in color, as well as it having reacted with the iodine that tests for starch (1). Powder B was identified as salt because of the prominent big pieces of grains and the dissolution that occurred over time. Powder C was identified as baking powder based off of its color change to purple when iodine was added and because of how it fizzed with all three liquids. Baking powder is a mixture of solids, which can include baking soda, a dry base, and a dry acidic material such as corn starch (3). Since baking powder contains a dry base and a dry acid, its reaction to all the liquids is explained. When an alkaline and a base mix, they react and produce a gas (4), which explains the fizzing. The dry acid in the baking powder was likely corn starch, explaining its color change to the iodine. Also, the corn starch (dry acid) reacted with the water and iodine--both bases, causing the frothing. Additionally, the baking soda component of the baking powder was responsible for the fizzy reaction to the vinegar because baking soda is a base and the vinegar is an acid. Powder D can be identified solely as baking soda because it only reacted to vinegar in the way that the baking soda in the baking powder did with the vinegar. Also, its white, grainy, powdery texture resembles baking soda, as well as its ability to mix with the other two liquids to form a pasty substance.

V. CONCLUSIONS

Overall, the experiment enforced the ability to use chemical indicators and basic chemistry and knowledge to identify simple unknown powder substances. Iodine is a chemical indicator that turns purple and was required to test the substances for starch in the experiment; this knowledge was acquired due to the experiment and the research conducted prior. Also, the information of basic base and acid reactions was learned throughout the experiment conducted. When a base and an acid react, the reaction may produce a gas, enforcing the formation of bubbles and showing a fizzing reaction. Lastly, the difference between physical and chemical changes was enforced during this experiment because some substances could only be identified through the physical appearance and physical changes that occurred when the liquids were mixed in.

Throughout the experiment there were various experimental errors, such as the amount of powder that was placed into each well. This could negatively affect the data, because the

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measurements were not accurate. Another experimental error was cross contamination of the powders because the wooden stick was a difficult measuring tool to use due to its flat narrow shape. A better instrument to measure and a specific amount of time allotted for the mixtures to finish reacting can be used for another experiment. Another thing that can be done next time would be the addition of new chemical indicators, such as Benedict's solution, and the addition of different acidic and alkaline liquids. The addition of various acids and bases could be used to test each individual substance with multiple liquids of differing pH levels and would allow the recording of the similarities and differences between the reaction.

VI. BIBLIOGRAPHY

1. Iodine solution Meaning in the Cambridge English Dictionary. (n.d.). Retrieved October 2, 2015,

2. Iodine (I) | chemical element. (n.d.). Retrieved October 2, 2015

3. The Difference Between Baking Soda and Baking Powder | . (n.d.). Retrieved October 2, 2015

4. Helmenstine, P. (n.d.). What Happens If You Mix an Acid and a Base? Retrieved October 2, 2015

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