68 The puzzle: Cathy Coldridge is an aspiring NYC chef who works in a very busy
ID: 1046126 • Letter: 6
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68 The puzzle: Cathy Coldridge is an aspiring NYC chef who works in a very busy kitchen in downtown Manhattan. Last week Cathy prepared a dish that contained boiled red cabbage. When she was draining the cabbage she noticed that the water she had used to boil it in had changed color from clear and colorless to purple. Cathy was fascinated by this and decided to pour the colored water into 5 glasses that were lying around the kitchen to observe the color more closely. When she poured the solution into the 5 glasses she was surprised to see the color of the solution change AGAIN. Cathy observed different color changes in each glass Her observations are summarized in the table below: Coe Glass # Observation Solution turned pink/red Solution turned green Solution stayed purple 4Solution turned yellow Solution turned blue Cathy is confused by these color changes and has come to you seeking help. 1. Identify the household chemicals that may remain in the bottom of each glass and hence cause the color of the solution to change. Quantify the acidity of each of these substances. 2. Rules of the game: 1. 2. 3. You must work on your puzzle in groups of 2 students. Each group will be given 1 leaf of red cabbage You have access to a selection of standard pH solutions and a selection of household substances. You may not use more than 5 mL of any solution at a given time. 4. Clues to help you solve the puzzle: 1. A standard pH solution is a solution of known pH. 2. A pH indicator is a solution that changes color in response to changes in pH. 3. To quantify the acidity of each substance you need to determine its pH value. Laboratory Experiment 7Explanation / Answer
The organic compounds that gives red cabbage it's red color are very sensitive to acidity. As long as they are acidic they stay red, but when they become non-acidic they turn blue. Red cabbage contains a water-soluble pigment called anthocyanin that changes color when it is mixed with an acid or a base. The pigment turns red in acidic environments with a pH less than 7 and the pigment turns bluish-green in alkaline (basic) environments with a pH greater than 7.When you boil red cabbage, the pigment dissolve into water and if the water turns purple, that means the pH of the water is neutral in nature. We can use the water in which red cabbage was boiled as an indicator to test the pH or chemical nature (in terms of acidic or basic) of other household chemicals.
1. For the first glass, the color turns to red/pink which is indicative of acidic substance in the glass such as vinegar which is essentially weak acetic acid or substance might be lemon juice which is citric acid.
2. For the second glass, the color turns to green which is indicative of a basic substance in glass such as baking soda, a weak base.
3. For the third glass, the solution stayed purple which indicates there might be drinking water in the glass as it is essentially neutral in nature.
4. For the fourth glass, the solution turned to yellow indicating a strong base. This might be household ammonia used for cleaning purposes.
5. For the fifth glass, the solution turned to blue indicating a very weak acid such as milk which contains lactic acid.
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