Ch.10.acids and alkalis (2nd week)
Transcript of Ch.10.acids and alkalis (2nd week)
![Page 1: Ch.10.acids and alkalis (2nd week)](https://reader035.fdocuments.us/reader035/viewer/2022062310/58d0b93f1a28ab1d3a8b5e51/html5/thumbnails/1.jpg)
Acids and AlkalisChapter 10Chemistry
2nd week
![Page 2: Ch.10.acids and alkalis (2nd week)](https://reader035.fdocuments.us/reader035/viewer/2022062310/58d0b93f1a28ab1d3a8b5e51/html5/thumbnails/2.jpg)
Detecting acids and alkalis
- Robert Boyle was an Irish scientist who lived 300 years ago.
- He decided to try and find and easy way to identify acids and alkalis.
- He knew that workers in France used plant juices to dye silk clothes.
- So he began testing plant juices to see if they would solve his problem.
![Page 3: Ch.10.acids and alkalis (2nd week)](https://reader035.fdocuments.us/reader035/viewer/2022062310/58d0b93f1a28ab1d3a8b5e51/html5/thumbnails/3.jpg)
- When he used red cabbage juice he found that:
Red cabbage juice
(purple)+ Acid Juice turns red
Red cabbage juice
(purple)+ Alkali Juice turns green
![Page 4: Ch.10.acids and alkalis (2nd week)](https://reader035.fdocuments.us/reader035/viewer/2022062310/58d0b93f1a28ab1d3a8b5e51/html5/thumbnails/4.jpg)
- When he used violets he found that:
+ Acid Juice turns Purple
+ Alkali Juice turns greenish yellow
![Page 5: Ch.10.acids and alkalis (2nd week)](https://reader035.fdocuments.us/reader035/viewer/2022062310/58d0b93f1a28ab1d3a8b5e51/html5/thumbnails/5.jpg)
- He discovered the colour change in litmus (juice from lichen)
- Litmus was used in laboratories around the world.
- It can be used as a solution of absorbed into paper strips.
![Page 6: Ch.10.acids and alkalis (2nd week)](https://reader035.fdocuments.us/reader035/viewer/2022062310/58d0b93f1a28ab1d3a8b5e51/html5/thumbnails/6.jpg)
![Page 7: Ch.10.acids and alkalis (2nd week)](https://reader035.fdocuments.us/reader035/viewer/2022062310/58d0b93f1a28ab1d3a8b5e51/html5/thumbnails/7.jpg)
- There are over 20 indicators that scientists use.
- 2 examples:- Methyl orange:Turns pink in acids.Turns Yellow in Alkalis.
- Phenolphthalein:Turns colourless in acid solutions.Turns Pink in alkaline solutions.
Acid Alkali
AlkaliAcid
![Page 8: Ch.10.acids and alkalis (2nd week)](https://reader035.fdocuments.us/reader035/viewer/2022062310/58d0b93f1a28ab1d3a8b5e51/html5/thumbnails/8.jpg)
pH scale- After indicators where found to identify acids and alkalis,
scientists wanted compare the strength of the acids and alkalis.
- In 1909, a Danish scientist called Soren Sorensen invented a scale called pH scale to compare the strengths.
- pH stand for ‘power of hydrogen’ because all acids hydrogen (active part in the chemical reactions)
- The pH scale starts from 0 – 14.
- The strongest acid is 0 and the strongest alkali is 14.
![Page 9: Ch.10.acids and alkalis (2nd week)](https://reader035.fdocuments.us/reader035/viewer/2022062310/58d0b93f1a28ab1d3a8b5e51/html5/thumbnails/9.jpg)
pH Classification0 - 2 Strong acid3 - 6 Weak acid
7 Neutral8 - 11 Weak alkali
12 - 14 Strong alkali
- N.B. An electrical instrument known as pH meter is used to measure pH accurately.
![Page 10: Ch.10.acids and alkalis (2nd week)](https://reader035.fdocuments.us/reader035/viewer/2022062310/58d0b93f1a28ab1d3a8b5e51/html5/thumbnails/10.jpg)
- The pH indicator is made of a mixture of indicators.
- Each indicator changes colour in the range shown in the scale.
- By combining the indicators a solution is made that gives different colours over the whole range of the scale
![Page 11: Ch.10.acids and alkalis (2nd week)](https://reader035.fdocuments.us/reader035/viewer/2022062310/58d0b93f1a28ab1d3a8b5e51/html5/thumbnails/11.jpg)