Most of the commodities people use at home are either basic or acidic. Acidic components can be identified through their ability to make things sour while basic or alkaline components have a slippery feel. The quantity of hydrogen ions in a substance determines if it is a base or an acid. The scale used to rate the number of hydrogen ions is called pH scale. It is numbered 1-14, with 1-6 being the pH levels for acids, bases having a pH of 8-14 and 7 being the pH for neutral items. pH indicators are used to measure pH and tell if a substance is either acidic or basic. While we have commercially made indicators, a person can make their indicator paper using some fruits or vegetables that contain the chemical that changes color when exposed to either acid or basic substance. This paper will cover the preparation of such an indicator using red cabbage, its use in measuring pH of common household commodities and compare the results to a universal indicator.
Purpose of Experiment
This experiment aims at making a homemade pH strip using red cabbage juice as the indicator and testing it on common household commodities to determine their pH and comparing the result with a commercial pH strip.
Null: There is no difference between commercial pH strips and homemade pH strips results when used on household substances
Alternative: There is a difference between commercial pH strips and homemade pH strips results when used on household substances
Acids ns bases are ancient concepts that have defined modern chemistry through their adoption and refinement. These groups have been known to be two of the largest, most significant groups in chemistry due to their numerous uses and effect on other components. These compounds have helped scientists account and understand countless chemical reactions. The knowledge of these compounds also helps in classifying household items and has been used in understanding biological systems, environment, and many industrial processes.
Acids are a distinct class of compounds that act as the proton (H+) donor. They can be an anion, cation or a neutral molecule. They exhibit the following characteristics: They are sour in taste. Acids react with certain metals to produce hydrogen gas, with bases to form water and salt and change blue litmus paper red. Their solutions conduct electricity due to the presence of free ions in a dissolved state. Examples include Vinegar, stomach acid HCl, and Citrus fruits.
Bases are compounds that act as proton (H+) acceptors. Bases are bitter, and their solutions produce a slippery, soapy feeling.They turn red litmus paper blue, and their solutions conduct electricity as they also form free ions; they break down in water to form negatively charged hydroxide ions (OH-) in water (Khan Academy, 2017).
A substance is classified as either basic or acidic based on the number of hydrogen ions relative to pure water. Acids have a higher concentration of H+ than water while a basic solution has lower H+ concentration. A pH scale is a numeric measure of H+ in a solution. It spans from 0-14, with compounds with a pH of 0-6 being acidic, those with 8-14 being basic and those with seven being neutral.
pH indicators are compounds that change their color to signal the concentration of H+ in a solution. Indicators exist as either dye infused paper strips or liquid dyes. pH indicators can be found in nature in flower petals (hydrangeas and Roses), fruits (strawberries, cherries) and vegetables (cabbage).
Red cabbage contains anthocyanin a chemical that changes color based on the acidity of the environment. It turns reddish-pink when acidic, purple when neutral and bluish green or yellow when basic. Figure 1 is the red cabbage indicator scale (DiscoveryExpressKids, 2015). It will be compared to the universal indicator scale (fig 2) (BBC, 2017).
Figure 1: Red Cabbage Indicator Scale
Figure 2: Universal Indicator Scale
Method and materials
1. Red Cabbage head
3. Chopping knife
5. A large glass bowl
6. Large glass measuring cup
7. Chemical splash goggles
8. Coffee filters
9. Cotton swabs
10. Small plastic cups
11. Ceramic dish
13. Distilled water
14. Universal indicator solution
15. Household substances
a. Clean shower
b. Rid of a bug
c. Palmolive soap
1. The experiment entails the use of knives and blender use care while handling them.
2. Wear goggles during the whole experiment, indicators and some if the household substances are chemicals. Do not mix any of the chemicals as it might cause a dangerous reaction.
3. All containers should be well-labeled
4. Red cabbage stains fabrics and clothes hence protect the working bench with newspaper. Wash your stained hands and skin with warm water and soap.
5. Test strips and cotton swabs should be thrown in the waste bin
6. Cabbage juice can be drained in the sink
7. List of household commodities can be flushed down the drain.
Preparation of pH Indicator Paper
1. Chop the red cabbage into small pieces using the chopping knife till you fill about 1 cup
2. Put the chopped cabbage in a blender and add 800ml of water. Blend till the cabbage is finely chopped
3. Using a strainer separate the liquid from the cabbage. Throw away the solid cabbage.
4. Pour the liquid into a large ceramic dish and label ‘red cabbage indicator.'
5. Cut the coffee filters into 2 * 6 cm strips.
6. Immerse the strips in the ceramic dish and allow the paper to soak till it is uniformly wet.
7. Remove the paper and let it dry in an area away from acid and alkaline vapors
Testing Household Substances
1. Cut the dried indicator paper into strips
2. Place small samples of household chemicals into cups and label the cups
3. Dip a cotton swab into one solution and spread it on an indicator paper
4. Do not reuse any of the strip indicator paper or the cotton swabs
5. Compare the color of the strip to the cabbage juice indicator scale and record your results
6. Repeat the tests using the universal indicator solution on household substances
7. Record our results
8. Clean up your workstation, discarding all cotton swabs and test strips according to the precautions stipulated and clean the plastic cups appropriately
These are the results acquired in the experiment.
Table 1: Results of pH levels using Commercial pH Strip and Homemade pH Strip
Well Plate Item tested Commercial pH Strip Homemade pH Strip
Color pH Color pH
1 Hydrochloric acid (HCl) Red 2 Red 2
2 Sodium Hydroxide (NaOH) Blue 12 Light Green 8
3 Distilled Water Dark green 10 Green 8
4 Gain Green 8 Light green 8
5 Palmolive soap Orange 6 Green 8
6 Rid a Bug Blue 12 Blue 12
7 Pine Sol Green 8 Dark green 10
8 Lysol Dark Green 10 Orange 6
9 Shout Green 8 Orange 6
10 Fabulous Green 8 Dark Green 10
11 Clean Shower Dark Green 10 Green 8
12 Awesome Blue 12 Dark Green 10
Discussion and Conclusion
Table 2: pH of Different Household Solutions Based on the Practical
Well Plate Item tested Acid/Base/Neutral Explanation
1 Hydrochloric acid (HCl) Acid pH falls below 7
2 Sodium Hydroxide (NaOH) Base pH falls above 7
3 Distilled Water Base pH falls above 7
4 Gain Base pH falls above 7
5 Palmolive soap Base pH falls above 7
6 Rid a Bug Base pH falls above 7
7 Pine Sol Base pH falls above 7
8 Lysol Acid pH falls below 7
9 Shout Acid pH falls below 7
10 Fabulous Base pH falls above 7
11 Clean Shower Base pH falls above 7
12 Awesome Base pH falls above 7
pH scale has a great significance in the scientific world because if helps test different products and in determining if they are acidic or basic and their level of acidic or basicity. According to the practical, homemade pH strips are just as effective as commercial pH strip in determining the pH of household commodities. We see no huge difference between the two results and they both lead to the same inference of basicity and acidity.
It can be inferred that the commercial pH strip is more sensitive though as it gives a vivid color change and hence better at reading. The colors for the home made strips are less vivid and hence harder to identify in the red cabbage indicator color scale. This can be due to human error during the process of making the homemade scale.
The practical provides sufficient evidence to support the null hypothesis that there is no significant different between homemade and commercial pH strips. The results for both strips are quite similar and lead to the same conclusion.
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