SE 402 8 pH Scale & Indicators
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Transcript of SE 402 8 pH Scale & Indicators
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4.1 – Describe how acids and bases in solution affect certain indicators
4.2 Determine the pH of a solution using a universal indicator
pH SCALE
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A scale of values that show how basic or acidic a substance is based on an
assigned number
http://www.downsizingamerica.com/images/ph_scale.gif
Strongest Strongest
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You have a glass of orange juice that has a pH of 3. What can you conclude about the orange juice?
It is an ACID
You have some drain cleaner that has a pH of 13.5. What can you conclude?
It is a BASE
You have some distilled water. What can you conclude about the pH? It is NEUTRAL, so pH = 7
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Which of the following substances would definitely have a pH under 7?
H2SO4 HCl H2OCaCl2 CH4 KOH Mg(OH)2
pH under 7 = ACIDS
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http://www.fishdoc.co.uk/images/pH_scale.gif
5
X 10 x 10 x 10 x 10….and so on
If substance A has a pH of 1 & substance B has a pH of 3, which is MORE ACIDIC?
Substance A – it is actually 100 times more acidic!!!
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Rank from most acidic to least acidic:
Vinegar pH 2Bleach pH 13Milk pH 6.5Coffee pH 5
Vinegar Milk BleachCoffeeLeast acidicMost acidic
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Rank from least basic to most basic:
Blood pH 7.4Sea Water pH 8Bananas pH 5Drain Cleaner pH 13.5
Bananas Sea Water Drain CleanerBloodMost BasicLeast Basic
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http://www.miamisci.org/ph/
Great internet site to explore…..Try the following three links on this site (EXCITE, EXPLORE and EXTEND) and play the interactive activities which will help you better understand pH!!
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Indicators are chemical dyes that turn different colours when they are placed in
acidic and alkaline (basic) solutions
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Methyl Red is an indicator & its colour change is shown below.
pH ScaleIndicator
1 2 3 4 5 6 7 8 9 10 11 12 13 14Methyl
Red RED Orange Yellow
If this indicator where placed in a solution with a pH of 6, what colour would it turn?
Orange
If this indicator where placed in a solution with a pH of 11.5, what colour would it turn?
Yellow
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The table below shows various indicatorsIf you have a solution of pH 5, what colour will it turn in each indicator?
YellowRedRedYellow/Orange
ColorlessYellowYellow
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•Universal Indicator (pH paper) is a special indicator.
•Like Litmus Paper, it uses color, but a much larger range of colors, closely identifying the pH of a solution relatively accurately.
Notice the colour range…•red shows very strong acid•orange/yellow is a weaker acid •green is neutral•blue/indigo shows weak base•purple/violet shows strong base
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Worksheet #7
Study guide, Module 3, page 22, 23, 24, 25 and 26
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References:
Google Images Microsoft Clip Art