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“PLANTS AS pH INDICATORS”
A Research Proposal Presented to
Mindanao State University Tawi-Tawi College of Technology and Oceanography SCIENCE HIGH SCHOOL Bongao, Tawi-Tawi
In Partial Fulfillment for the Requirements for Graduation
MORENA E. DAIL PARAMISULI S. AMING SHEA ISSEY M. ANUDDIN ALNEEHADA BIANCA A. KAMSA
TABLE OF CONTENTS
Title Page Table of Contents CHAPTER I – INTRODUCTION Background of the Study Statement of the Problem Significance of the Study Hypothesis Scope and Delimitation of the Study Operational Definition of Terms CHAPTER II – REVIEW OF RELATED LITERATURE CHAPTER III – MATERIALS AND METHODS Research Method Materials Equipments/Apparatus Procedure Preparation of pH Indicators Collection and Preparation of Samples Extraction of Coloring Matter/pH Indicator Testing Different Items for pH level/Determination of the Color Changes of Different Plants when used as Indicator Comparing Color Changes Flow Chart of the Procedures
CHAPTER I INTRODUCTION Background of the Study pH is a measurement that will denote the level of chemical activity of hydrogen in a given solution. The lowest possible pH rating is a pure acid at 0, and the highest possible pH rating is a pure acid at 0, and the highest possible pH is at 14, which is a pure base. (Litherland, 2009) Commercial pH indicators are hard to find. Though they are cheap, many people have trouble finding them. People really don’t have to use them, as nature provides us with pH indicators in the form of plant pigments known as anthocyanins, which change color over different pH ranges, depending on source. The plants that have anthocyanins are called natural pH indicator or plant pH indicators which are cheaper and easier to find than the commercial ones. Methods of determining the pH of a solution can be expensive as well as indeed cumbersome to use. Natural indicators, on the other hand, are relatively inexpensive by comparison. This cheap cost is what makes them ideal for situations where a large number of tests will have to be done. Some examples of this could be in a high school or college chemistry lab. There are schools that lack pH indicators, particularly in some remote areas. One such is the MSU TCTO Science High School. Sometimes, it is not available in a specific area. Some are forced to go to other places just to acquire some samples. That is why this study
will focus on the production of the available pH indicator out of different plants as alternative for the commercial pH indicators. In recent years, the demand for measuring pH has grown dramatically. This includes agricultural, wastewater, pharmaceutical, and educational applications, critical measurement in industries, testing a sample against a legal requirement, and is also of outstanding importance in water and environmental analysis. Since almost any highly colored fruits, vegetables, or plants contain anthocyanin, then it is hypothesized that pH indicators can possibly be produced out of different plants and that they can be used to identify the color changes of different household and laboratory chemicals. Moreover, there has been a growing need to utilize indigenous resources as materials in the laboratory. The results of this study can be a basis for use of plants that are locally available in the province and in the country, as a cheaper, alternative, and important aid in chemistry.
Statement of the Problem/Objectives This study aims to produce pH indicators out of different plants. Specifically, it will seek to answer the following questions: 1. What are the colors produced by the household chemicals and the laboratory
chemicals after the addition of each plant extract? 2. What are the colors produced by the laboratory chemicals after the addition of
each plant extract?
Significance of the Study This study will focus mainly in the production of pH indicators using different plants. Though there are many commercial indicators in our modern world today, there is still a possibility that a time of scarcity of indicators may occur. If time of scarcity happens, one knows how to easily make an indicator out of natural materials.
Scope and Delimitation of the Study This study will focus on the production of pH indicator out of different plants. Aluminum sulfate will be used as an additive that will be applied on each test. The household chemicals that will be used in this study are muriatic acid, calamansi extract, feminine wash, vinegar, shampoo, distilled water, monosodium glutamate, bath soap and detergent bar powder solution and household chemicals such as HNO3, H2SO4, CuSO4, K2Cr2O7, Cr(NO2)3, Pb(NO3)2, Ammonium Hydroxide, Ca(OH)2, and NaOH. The study will be conducted in the MSU Science High School Laboratory Room. A total of ten (10) indicators will be used. Eight (8) of which are plant indicators: Red Cabbage, Purple Heart Plant leaves, Areca Nut, Eggplant, Muntingia, Red Onion, Malabar Nightshade, and Mangosteen; the other two are synthetic: phenolphthalein and litmus paper. Operational Definition of Terms
For the purpose of clarification, the following key terms are hereby operationally defined.
Acid – a compound usually having a sour taste and capable of neutralizing alkalis and reddening blue litmus paper Anthocyanin – are water-soluble vacuolar pigments that may appear red, purple, or blue according to the pH. It may occur in tissues of most ph indicating plants, including leaves, stems, roots, flowers, and fruits Base – it is a compound usually having a slight bitter taste and capable of turning blue a red litmus paper Strong Acid/Base – an acid or base that completely dissociates into ions Weak Acid/Base – an acid or base that only partially ionizes in solution pH – measure of the acidity of a substance; a ph of less than 7 is acidic (lower number=more acidic) and a pH of greater than 7 is basic, in general the scale goes from 1 (very acidic) to 14 (very basic) pH indicator – substances that changes color depending on the pH of the solution it is mixed with. Indicators are often made from plant extracts plant indicators – plants that can be used as an indicator. The plant extracts are usually used as an indicator
CHAPTER II REVIEW OF RELATED LITERATURE
This chapter presents the review of related literature that provides information about “Plants as pH Indicators” which also serves as guidance in the research process, formation of research problem, hypothesis, and definition of terms. A pH (potential of Hydrogen) measurement reveals if a solution is acidic or alkaline (also base or basic). If the solution has an equal amount of acidic and alkaline molecules, the pH is considered neutral. Very soft water is commonly acidic, while very hard water is commonly alkaline, though unusual circumstances can result in exceptions. (Kayne, 2003) pH is defined as the negative logarithm of the hydrogen ion concentration. This definition of pH was introduced in 1909 by the Danish biochemist Soren Peter Lauritz Sorensen. The pH value is an expression of the ratio of [H+] to [OH-] (hydroxide ion concentration). Hence, if the [H+] is greater than [OH-], the solution is acidic. Conversely, if the [OH-] is greater than the [H+], the solution is basic. At pH of 7, the ratio of [H+] to [OH-] is equal and, therefore, the solution is neutral. pH is a logarithmic function. A change of one pH unit represents a 10-fold change in concentration of hydrogen ion. (Kohlmann, 2003) An indicator is a chemical substance that, by being able to change color, provides visual evidence of the nature of chemical system in which it is placed. Most indicators are complicated organic molecules that exists in two different color form (sometimes one form is colorless) in different chemical environments such as acidic and basic solutions. The most common acid-base indicator is litmus paper – paper that is treated with a chemical that appear red in acidic solutions (low pH) and blue in basic solutions (high ph). (Knecht, 1996 quoted by Manulon, 2007)
The most common method to get an idea about the pH of solution is to use a pH indicator, which is also called an acid-base indicator. An indicator is a large organic molecule that works somewhat like a “color dye”. Whereas most dyes do not change color with the amount of acid or base present, there are many molecules, known as acid-base indicators, which do respond to a change in the hydrogen ion concentration. Most of the indicators are themselves weak acids. (Ophardt, 2003) Indicators are complicate organic weak acids or bases with complicated structures. They are also called acid-base indicators or neutralization indicators. Their conjugate sac indicators and ions for basic indicator. The ionization of acidic indicator in a solution is represented by the equilibrium. (Khan et al., 2011) Indicators work because they are weak acids which, when in solution, exist in equilibrium with their conjugate base. The acid and its conjugate base each have different colors, and as the equilibrium shifts from one direction to the other, the color of the indicator solution changes. Some indicators exhibit only two colors and some exhibit wide range. Each indicator must be individually studied to determine its behavior as a function of pH. (Malapit, 2010) Chemists pick selective natural dyes to indicate specific pH levels based on their color changes. For example, a commonly used acid-base indicator, named Bromthymol Blue, is yellow in acid and blue in base and intermediate in between at pH 7. Yellow form of Bromthymol Blue, (acid form HBb) when it donates a proton to OH- ions at higher pH changes to anion, (base-form, Bb) which is blue. The point at which a color changes from intermediate
to blue gives information on the acid strength of the acid-form, HBb. Chemists test various indicators for their acid strength and choose an indicator for specific pH levels. (Withers, 2010) There are hundreds of different acid-base indicators, many of which can be extracted from common plants. (Malapit, 2010) Anthocyanins are water soluble pigments found in many plants. These pigments have several functions in the plant, and they are also of nutritional interest, because they have been linked with nutritional benefits such as cancer prevention. People eat anthocyanins everyday, and many people have a diet rich in these pigments. Depending on pH, anthocyanins can be red, blue, or violet. The bright red color of an apple is due to the presence of anthocyanins, as is the rich blue of a blueberry. These pigments can be found in fruit, stems, and leaves, and their levels may fluctuate. (Smith, 2003) Anthocyanin is probably the most readily available acid/base indicator; it is the plant pigment that makes red cabbage purple, cornflowers blue, and poppies red. It changes color from red in acid solution to purplish to green in mildly alkaline solution to yellow in very alkaline solution. (Senese, 1997) Many plant pigments act as acid-base indicators, and one can know appreciate why some of these pigment molecules behave the way they do. The blue and red pigments of flowers were isolated and extensively studies by R.M. Willstatter, just before the outbreak of the First World War. Many indicators can be extracted from plants. The substance in the plant changes at the molecular level which causes their color to be different at different pH levels.
Red cabbage juice a natural pH indicator which is known to contain anthocyanins which are pigments that react in a different way to acids and bases. (Chandrasekaran, 2001) The substances in plant products such as tea, red cabbage or grapes react with acids (or bases) resulting in changes at the molecular level which causes their colors to be different at different pH levels. All pH indicators, such as litmus paper, change color depending whether they donate or accept protons, (acids are proton donors and bases are proton acceptors). Therefore, pH indicators are themselves acids or bases. (Withers, 2001) Natural indicators have been used for hundreds of years, long before chemists made synthetic acid-base indicators. The 17th century chemist, Robert Boyle described indicator extracted from roses and other plant materials in his book “The Experimental History of Colours”. Boyle included the ability to turn plant juices red among the properties of acids. Red cabbage is not the only natural indicator that goes through a variety of color changes but there are some other compound from plant origin that can act as indicators. Many of the natural dyes have extracted and isolated from different parts of plants which have different colors at different pH. It is also observed that some extracts exhibit different color at different pH values. Cherry juice, for example, may be red (pH=7), or green (pH=10). Roses, turnip skins, violets, plum skins, primroses, radish skins, hydrangeas, rhubarb skins, cherries, blue berries, red grapes, beets, red wine, curry powder, geranium petals, grape juice concentrate, etc. are only a few of many that have different colors in acid or base. Almost any highly colored fruit, vegetable, or flower petal has the potential use as an acid-base indicator. (Khan, et al., 2011)
CHAPTER III MATERIALS AND METHODS
This chapter presents the methods, research design, data collection, materials and the procedures that will be used in the study. Research Method The study is a descriptive one but will utilize an experimental design. Materials The materials that will be used in the study are the following: household chemicals, such as muriatic acid, calamansi extract, feminine wash, vinegar, shampoo, distilled water, monosodium glutamate, bath soap, detergent bar and powder solution, toothpaste, laboratory chemicals such as HCl, HNO3, H2SO4, CuSO4, K2Cr2O7, Cr(NO3)3, Pb(NO3)2, Ammonium Hydroxide, Ca(OH)2, NaOH, Aluminum Sulfate and 1000 grams of each plant indicator such Red Cabbage, Purple Heart Plant leaves, Areca Nut, Eggplant, Muntingia, Red Onion, Malabar Nightshade, Mangosteen, and synthetic indicators, such as litmus paper strips, and phenolphthalein. Equipments/Apparatus and Utensils Nine beakers (100 mL), 190 test tubes, medicine dropper, knife, pot, strainer, and stirring rod will be used in the study.
Procedure Collection and Preparation of Samples
One thousand grams of each plant will be gathered and washed thoroughly. Each plant may either be placed in a pot to boil or in a blender. In the case of mangosteen or red cabbage, for example, both of them may just be boiled. Extraction of Coloring Matter/pH indicator Each plant will be chopped into smaller pieces and 500 g of each chopped plant will be placed in a blender with 350 ml distilled water. The plants will be blended separately. Each plant extract or liquid will then be poured into separate containers. In the case of mangosteen or red cabbage, the pieces will be placed in separate container with enough boiling water to cover for at least 10-30 minutes. The contents of the bowl will then be gently tipped into a sieve to drain it into another bowl. Coffee filter will be used to remove the smaller pieces. The liquid will then be poured into separate containers.
Testing Different Household/Laboratory Chemicals for pH level/Determination of the
Color Changes of Different Plants when used as Indicators
Twenty test tubes will be labeled for each plant extract (ten for household chemicals and another ten for the laboratory chemicals). 5 ml of each household or laboratory chemical will be poured into each test tube. In the case of powdery ingredients such as the washing powder, we will be mixed with water to form the solution, just like liquid chemicals. Drops of each plant extract will be added into each test tube. Each mixture will be stirred very well to see if there are any color changes in each solution. The procedure will be the same for all plants and synthetic indicators (like litmus paper of phenolphthalein) will also be used to determine the acidity or basicity of the chemicals.
Comparing Color Changes The results will be recorded to compare the color changes of the household chemicals when treated with each plant indicator and with synthetic ones.
REFERENCES Books Kohlmann, Frederick J. “What Is pH and How is it Measured?” Hach Company, 2003; 3-6
Ophardt, Charles E. “Virtual Chembook: Acid and Base Indicators,” Elmhurst College. 2003 Theses and Journals Chandrasekaran, Jayanthi. “Chemistry of Colours,” Jawaharlal Nehru Center for Advanced Scientific Research Bangalore, India. 2001. Khan, Pathan Moh’d Arif et al, “Journal of Advanced Scientific Research, Mumbai India. 2011; 2(4):20-27 Malapit, Christian, “Plant Extracts as Acid-Base Indicators,” Ateneo de Manila University: Department of Chemistry. 2010 Manulon, Yusuf Khan N. et al, “Mangosteen Rind (Garcinia Mangostana) : A Potential pH Indicator,” an Investigatory Project, a Requirements for Graduation, MSU TCTO Science High School, Bongao, Tawi-Tawi. 2009 Tangkusan, Denzy Rose I. and Alih, Raisha T. “Red Onion (Allium Cepa Linn): A Potential pH Indicator,” an Investigatory Project, a Requirements for Graduation, MSU TCTO Science High School, Bongao, Tawi-Tawi Vedad, Jamela R. “Cassava Leaf Extract as Acid Base Indicator,” an Investigatory Project, Philippine Science High School Bicol Region Campus, 2005-2006 Internet Sources Helmenstine,
Kayne, R. “WiseGeek: What is pH?” ed. Wallace, O. Conjecture Corporation. 2003 Litherland,
Smith, S.E. “WiseGeek: What are Anthocyanins?” ed. Wallace, O. Conjecture Corporation. 2003 Withers, Gayathri. “NATURAL INDICATORS: HOW DO THEY WORK?”. GIPSE. 2001
SCIENTIFIC NAME Brassica oleracea var.
capitata f. rubra Purple Heart Plant
Areca catechu L.
Solanum melongena L.
Muntingia calabura L.
Flow Chart of the Procedure
Collection of the Plants
Allium Cepa L. Brasella
Add drops to
Color Outcome/Color Change
Color Outcome/Color Change