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

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.gifhttp://www.downsizingamerica.com/images/ph_scale.gif

StrongestStrongest StrongestStrongest

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

Which of the following substances would definitely have a pH under 7?

H2SO4H2SO4 HClHCl H2OH2O

CaCl2CaCl2 CH4

CH4 KOHKOH Mg(OH)2Mg(OH)2

pH under 7 = ACIDSpH under 7 = ACIDS

http://www.fishdoc.co.uk/images/pH_scale.gifhttp://www.fishdoc.co.uk/images/pH_scale.gif

5

X 10 x 10 x 10 x 10….and so onX 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!!!

Rank from most acidic to least acidic:

Vinegar pH 2Bleach pH 13Milk pH 6.5Coffee pH 5

Vinegar Milk BleachCoffee

Least acidicMost acidic

Rank from least basic to most basic:

Blood pH 7.4Sea Water pH 8Bananas pH 5Drain Cleaner pH 13.5

Bananas Sea Water Drain CleanerBlood

Most BasicLeast Basic

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!!

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!!

                                                    

  

Indicators are chemical dyes that turn different colours when they are placed in

acidic and alkaline (basic) solutions

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 14

Methyl 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

The table below shows various indicators

If you have a solution of pH 5, what colour will it turn in each indicator?

Yellow

Red

RedYellow/Orange

Colorless

Yellow

Yellow

•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 color 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

Worksheet #7

Study guide, Module 3, page 22, 23, 24, 25 and 26

References:

Google Images Microsoft Clip Art