ENGAGE PHASEOne day, a student drops in at the stall to get a drink. At the stall, she order orange juice and afterdrank she noticed that the orange juice taste sour than usual. So, she wonders how concentrationof orange juice influences its taste and why mostly drink has different taste. She also thinks howpH can lead to disease like cancer.EMPOWER PHASEIntroductionFrom our group discussion, we decided to choose experiment that test the pH level of commondrinks using the data logger. The pH data logger that we choose is DrDAQ data logger. DrDAQis used here as a pH meter with the addition of a pH probe to measure the pH level over theentire pH scale of a range of common drinks. Recently dentists have begun warning about thedangers of drinking acidic drinks. Teenagers, they suggest, who drink large amounts of fizzy„pop‟ drinks suffer from tooth erosion whereby the enamel covering of the tooth is dissolved bythe acid in the drink. Athletes are also at risk from drinking sports drinks. The recommended„safe‟ level for the pH of drinks is 5.5, Anything below this can promote tooth erosion. Thisexperiment looks at the relative pH values of different drinks and can be used to determinewhether a particular drink is „safe‟ according to the above criteria. It can also be used as a goodintroduction to further studies into tooth decay and enamel stripping. It is suitable for ages 14+and requires some knowledge of the pH measurement. Actually, measurement of pH for aqueoussolutions can be done with a glass electrode, pH meter or by using indicator. However, throughthis experiment to test pH level in common drink, the method use to measure the level of pH isby using pH meter by apply DrDAQ as a data logger.All foods and drinks have their own pH levels which have risk to affect the pH of human body.In chemistry, pH is a measure of the activity of the hydrogen ion. More clearly, pH is theuniversally accepted scale for the concentration of hydrogen ions in an aqueous solution. Acommon drinks pH can be measure either in acidic state, neutral or alkaline state. An ideal pH isbetween seven to seven and half on the scale from one to 14. The human body can functionsoptimally at alkaline conditions which is about at pH 7.4. It is necessary to maintain a healthy pH
level to make sure there is not too much acid interferes with our blood cells that have ability totransport oxygen.Drinking certain beverages also can increase our pH level. So that DrDAQ is used as a meterwith the addition of a pH probe to measure the pH level in the common drinks such as orangejuice and apple juice. Orange juice is one of the famous juices among the others in this world.This is according to the Drink Secrets website. Recently, dentists have begun warning about thedangers of drinking acidic drinks. Teenagers, they suggest, who drink large amounts of fizzy„pop‟ drinks suffer from tooth erosion whereby the enamel that covering the tooth is dissolved bythe acid in the drink. Moreover, athletes also face the same problem and have to take riskbecause they drinking sports drink.This experiment looks at the relative pH values of different kinds and can be used to determinewhether a particular drink is safe according to the criteria that had been stated. Moreover, it isalso can be used as a good introduction to further studies into tooth decay and enamel stripping.Furthermore, it is also introduction for using data logging that can operate independently of acomputer unlike many other types of data acquisition devices. Moreover, data loggers morepowerful programmable devices which are capable of handling hundreds of inputs.A data logger is an attractive alternative to either a recorder or data acquisition system in manyapplications. When compared to a recorder, data loggers have the ability to accept a greaternumber of input channels, with better resolution and accuracy. Also, data loggers usually havesome form of on-board intelligence, which provides the user with diverse capabilities. Forexample, raw data can be analyzed to give flow rates, differential temperatures, and otherinterpreted data that otherwise would require manual analysis by the operator.The major difference between a data logger and a recorder, however, is the way the data itself isstored, analyzed and recorded. A common recorder accepts an input, and compares it to a fullscale value. The pen arm is then deflected across the recording width, to produce the appropriateratio of the actual input to the full scale input. For example, using a recorder with a 1 Volt fullscale, an input of 0.5 Volts would move the pen 0.5/1 or 50% of the distance across the recordingwidth. In comparison, a data logger accepts an input which is fed into an analog-to-digitalconverter prior to analysis and storage. This method has advantages in accuracy and resolution,
while only a recorder can provide a truly continuous trend recording. Data loggers can also offeradvantages over dedicated, computer interface systems. A data logger is a self contained unit,which does not require a host to operate. It can be installed in almost any location, and left tooperate unattended. Data loggers have a distinct advantage over conventional interface devices,in that they operate in this stand-alone mode, and yet have the capability to “dump” or transferthe data to a host system, if required. Most data loggers have the ability to work similarly tostandard recorders, in that they provide the user with a hard copy printout of the data recorded.This data can be immediately analyzed for trends, or stored for historical archive purposes. Dataloggers can also monitor for alarm conditions, while recording a minimum number of samples,for economy. If the recording is of a stead-state nature, without rapid changes, the user may gothrough rolls of paper, without seeing a single change in the input. A data logger can record atvery long intervals, saving paper, and can note when an alarm condition is occurring. When thishappens, the event will be recorded and any outputs will be activated, even if the event occurs inbetween sample times. A record of all significant conditions and events is generated using aminimum of recording hardcopy.The differences between various data loggers are based on the way that data is recorded andstored. The basic difference between the two data logger types is that one type allows the data tobe stored in a memory, to be retrieved at a later time, while the other type automatically recordsthe data on paper, for immediate viewing and analysis. Many data loggers combine these twofunctions, usually unequally, with the emphasis on either the ability to transfer the data or toprovide a printout of it. The example of data loggers are temperature, flow and level, pH andconductivity, data acquisition, pressure, strain and force, and heaters. Each data logger can beuse in many experiments such as air velocity indicators, doppler flowmeters, level measurement,magnetic flowmeters, environmental instrumentation, pH electrodes and instruments, water andsoil analysis instrumentation.Equipment required
1. DrDAQ data logger connected to a PC 2. One pH sensor (DrDAQ Part no DD011) 3. Containers for the drinks (we used plastic drinking cups) 4. A selection of common drinks - we used: a) Orange Juice b) Apple Juice c) Black Coffee d) Black Tea e) Lemon Tea f) Original Coke g) Pepsi h) Cherry Coke i) Ribena j) Lemon Squash k) MilkExperiment set up 1. Fill all cups with an equal amount of liquid which will cover the pH probe tip. 2. Mark the cups so that they can be identified later. 3. Plug the pH probe into DrDAQ and run PicoLog software. 4. Optionally, you can calibrate the pH probe using buffer solutions. 5. It is important to allow all the drinks to stabilise at room temperature since pH readings vary with temperature.
Diagram showing the experiment set upCarrying out the experimentHere is a table showing the pH of some common substances for reference.Before starting the experiment, make a table listing drinks that you will test and indicate whatyou expect the pH of each drink to be.
Create your table as shown below: Gently agitate the pH probe in each liquid for a minute or two while the pH reading settles then record the reading in the table and move onto the next liquid. NOTE Take care to thoroughly clean the pH probe in a large container of water between each liquid to reduce cross contamination of the liquids. When you have tested all your available drinks, plot the results on a bar graph with each bar showing the expected value and recorded value for each liquid.Result Drinks pH Apple juice 3.49 Orange juice 3.84 Black tea 6.37 Black coffee 5.51Questions and discussion of results The formula for pH is:Q1. With respect to the results you have obtained, can you make any predictions about the likelypH values of the foods and drinks we consume ?In chemistry, pH is a measure of the activity of the hydrogen ion. Pure water has a pH very closeto 7 at 25°C. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater
than 7 are basic or alkaline. With respect to the results we have obtained, we can predict that thepH of the majority tested drinks are acidic and neutral.Q2. Find the pH of a solution whose is 9.5E-8MBased from the question number 2, when the concentration of hydrogen ion, [H+] is 9.5x10-8 M,the pH value is, pH = - log [H+] = - log (9.5 x 10-8 M) = 7.02Q3. Calculate the of a solution with a pH of 5.45From question number 3, a solution with a pH of 5.45 has the concentration of hydrogen of 3.5 x10-6 M. The calculation is as follow: pH = - log [H+] [H+] = anti -log (-5.45) = 3.5 x 10-6 M Q4. How does the pH reading of a liquid vary with temperature? (possibly heat a buffer solution) Lets begin with the words acidic and basic as extremes which describe solutions as hot and cold are extremes which describe temperature. Just as mixing hot and cold water evens out the temperature, mixing acids and bases can cancel their extreme effects and is then considered neutral. pH is a scale that is used to measure a substances acidity. pH scale can tell if a liquid is more acid or more base, just as the Fahrenheit or Celsius scale is used to
measure temperature. The range of the pH scale is from 0 to 14 from very acidic to verybasic. A pH of 7 is neutral. A pH less than 7 is acidic and greater than 7 is basic. Each wholepH value below 7 is ten times more acidic than the next higher value. For example, a pH of 4is ten times more acidic than a pH of 5 and a hundred times (10 X 10) more acidic than a pHof 6. This holds true for pH values above 7, each of which is ten times more basic (alsocalled alkaline) than the next lower whole value. An example would be, a pH of 10 is tentimes more alkaline than a pH of 9.While an absolutely accurate measurement of pH levels requires advanced equipment, arough measurement can be made with pH test strips. An acid-base indicator is a weak acid ora weak base. A staple of chemistry labs all around the world, these inexpensive strips aresimply dipped into the liquid whose pH level is being gauged. After a short while, the colorof the strip will change, and the final color is then compared to the rainbowlike color paletteon the package, where each shade is assigned a pH number. Darker colors usually mean ahigh pH value, while lighter colors indicate low pH levels. Indicators have a very usefulproperty - they change color depending on the pH of the solution they are in. This colorchange is not at a fixed pH, but rather, it occurs gradually over a range of pH values. Thisrange is termed the color change interval. Each pH indicator is defined by a useful pH range.
For example Phenolphthalein changes from colorless at 8.0 to pink at 10.0. And Bromthymol Blue has a useful range from 6.0 (yellow) to 7.6 (blue). Temperature will have a measurable yet very slight effect on the pH of water. In fact, pure water has a pH of exactly 7 only at 25 degrees Celsius, or 77 degrees Fahrenheit. As the water temperature goes up, pH goes down. The converse is also true, in that colder water has a higher pH value. At 60 degrees Celsius (140 degrees Fahrenheit), pure water will register a pH value of 6.96. In other words, the change is very slight and cannot be registered with crude measurement techniques such as pH test strips. The reason temperature affects waters pH is that water molecules tend to break down into their constituents, hydrogen and oxygen, as the temperature increases. As temperatures increase, a larger proportion of water molecules break up, producing more hydrogen, which then increase the pH of the water.ENHANCE PHASE According to the problem statements in engaging phase, the students tasted his orangesjuice to be sourer than it should be. He was doubt on how the concentrations of the juice affectthe taste and why the tastes of various drinks are different. He also thinks why pH leads todiseases such as cancer. Basically, the tastes are due to the pH value. Technically, the pH of asolution depends on measuring concentration. The pH value in acidic range for the highconcentration of solution is lower than the pH value for the solution that is high in concentration.High concentration solution has high concentration of H+. The concentration of H+ leads thevalue of pH. For example, the concentrations of 0.02 M of solution have low pH than the 0.05 Msolution. The concentration of the juice is maybe higher than usual. The taste for the acidic issour. Besides that, various drinks have different tastes because pH values of the drinks aredifferent. Some of the drinks are sour because it is acidic and the others are bitter because it isbasic or alkaline. There are also neutral drinks with pH 7.
Consumption of many acidic foods can lead to severe diseases such as cancer becauseacidic conditions inhibit nerve action in our human body. That is why we should balance our dietas it helps to maintain the pH balance of the blood. When we consume more acidic food, ourblood will develop a more acidic condition. Then the body will inevitably deposit the excess acidto another area of the body so that the blood will be able to maintain an alkaline condition. Asthis cycle continues, these areas will increase in acidity and some cells will die. The dead cellswill then turn into acids. Some cells may adapt and instead of dying as normal cells do in an acidenvironment, they will survive by becoming abnormal. These abnormal cells are known asmalignant cells. Malignant cells do not correspond with brain function or with our DNA memorycode. Malignant cells grow indefinitely and without order. This malignant cell is known ascancer.