Acids and alkalis

7,209 views

Published on

Published in: Education
0 Comments
7 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
7,209
On SlideShare
0
From Embeds
0
Number of Embeds
511
Actions
Shares
0
Downloads
429
Comments
0
Likes
7
Embeds 0
No embeds

No notes for slide
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • The results for the litmus tests are:
    Tube 1. The solution is an alkali which turns blue when red litmus is added to it and remains blue when blue litmus is added to it.
    Tube 2. The solution is an acid which remains red when red litmus is added to it and turns blue when red litmus is added to it.
    Tube 3. The solution is water which remains red when red litmus is added to it and remains blue when blue litmus is added to it.
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • <number>
  • Acids and alkalis

    1. 1. Chemistry Acids and Alkalis 1 of 34 20 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    2. 2. Contents 7E Acids and Alkalis What are acids and alkalis? Hazard symbols Indicators and the pH scale Neutralization Summary activities 1 of 34 20 2 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    3. 3. What is an acid? Acids are a group of chemicals. What do you know about acids? Are all acids dangerous? 1 of 34 20 3 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    4. 4. What is an acid? Acids are a group of chemicals. Which of these items contains an acid? everyday acids laboratory acids Can you think of other examples of acids? 1 of 34 20 4 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    5. 5. What is a weak acid? Acids are found in household items such as food, drink and beauty/skincare products. It is safe to handle these acids and even taste them, if they are for eating! These acids are known weak acids. 1 of 34 20 5 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    6. 6. What is a strong acid? Some acids, like those found in the laboratory or a car battery, are very dangerous (too dangerous to taste or touch). These acids are said to be corrosive as they can damage other materials by wearing them away! They are strong acids. Why must strong acids always be handled very carefully? 1 of 34 20 6 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    7. 7. What is an alkali? Alkalis are another group of chemicals, the opposite of acids. Which of these items contains an alkali? everyday alkalis laboratory alkalis Can you think of other examples of alkalis? 1 of 34 20 7 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    8. 8. What is a weak alkali? Alkalis are found in soaps and other materials used for cleaning. It is safe to handle these alkalis, which can feel soapy. These alkalis are known as weak alkalis. 1 of 34 20 8 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    9. 9. What is a strong alkali? Some alkalis, like those in the laboratory or in cleaning materials such as toilet cleaner, are too dangerous to touch. These alkalis are said to be caustic because they can burn skin and damage other materials! They are strong alkalis. Why must strong alkalis always be handled very carefully? 1 of 34 20 9 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    10. 10. Contents 7E Acids and Alkalis What are acids and alkalis? Hazard symbols Indicators and the pH scale Neutralization Summary activities 1 of 20 10 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    11. 11. What are hazard symbols? How can you tell which chemicals are safe and which are dangerous? Special symbols are used on bottles and vehicles that contain dangerous chemicals. i toxic irritant h harmful corrosive highly flammable These hazard symbols show why the chemical is dangerous. Why is it important that these symbols can be recognised by people from other countries? 1 of 20 11 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    12. 12. What do hazard symbols mean? 1 of 20 12 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    13. 13. Contents 7E Acids and Alkalis What are acids and alkalis? Hazard symbols Indicators and the pH scale Neutralization Summary activities 1 of 20 13 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    14. 14. What is an indicator? How can you test a liquid to find if it is an acid or an alkali? An indicator is a special chemical that changes to a different colour in an acid or an alkali. Litmus paper and litmus solution are examples of indicators. Litmus is red in acid. 1 of 20 14 of 34 Litmus is blue in alkali. © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    15. 15. Litmus test experiment 1 of 20 15 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    16. 16. What is universal indicator? Litmus is used to show if a solution is acid or alkali. Litmus does not show if the acid or alkali is weak or strong. Universal indicator has a range of colours that show how weak or strong the acid or alkali is. stronger acid strong acid stronger alkali weak weak acid neutral alkali strong alkali What is the colour for a weak acid? What is the colour for a strong alkali? 1 of 20 16 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    17. 17. What is the pH scale? The strength of an acid or alkali is measured by the pH scale. Each universal indicator colour is given a number called the pH value. Universal indicator can tell you the pH of a solution. stronger acid 1 2 3 4 5 6 strong acid stronger alkali 7 8 9 10 11 12 13 14 weak weak acid neutral alkali strong alkali What is the pH of a weak acid? What is the pH of strong alkali? 1 of 20 17 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    18. 18. What is the pH? 1 of 20 18 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    19. 19. What type of substance? Are these substances acidic or alkaline? Are they weak or strong? Substance pH Description of acid/alkali soda water 6 car battery acid 1 very weak acid very strong acid soap 8 very weak alkali washing soda 10 weak alkali stomach acid 2 strong acid oven cleaner 14 very strong alkali vinegar 4 weak acid acid 1 of 20 19 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 alkali © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    20. 20. Contents 7E Acids and Alkalis What are acids and alkalis? Hazard symbols Indicators and the pH scale Neutralization Summary activities 1 of 20 20 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    21. 21. Mixing an acid and an alkali What happens when an acid and an alkali are mixed? ? Mixing an acid and an alkali causes a chemical change. This chemical change is called a chemical reaction. How do you know this chemical reaction has taken place? 1 of 20 21 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    22. 22. What is neutralization? The chemical reaction between an acid and an alkali is called neutralization. acid alkali a salt water What happens to the pH value of the reaction mixture during neutralization? The pH value of the reaction mixture becomes closer to 7. 1 of 20 22 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    23. 23. What is neutralization? The chemical reaction between an an acid and an alkali can be written as: acid alkali a salt water What are the two new substances produced by a neutralization reaction? 1 of 20 23 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    24. 24. Neutralization and indigestion 1 of 20 24 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    25. 25. Neutralizing stings A bee sting is acidic. Why can bicarbonate of soda (pH 9) be used to treat a bee sting? 1 of 20 25 of 34 A wasp sting is alkaline. Why can vinegar (pH 3) be used to treat a wasp sting? © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    26. 26. Neutralizing soil Soils in different places can be acidic, alkaline or neutral. Many plants do not grow well in acidic soil. Why do farmers test soil to check the pH? Farmers often add an alkali to acidic soil to make their plants grow better. How does the alkali help to treat the acidic soil? 1 of 20 26 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    27. 27. Neutralizing acid rain Gases emitted by cars, power stations and factories mix with rainwater in the atmosphere. This rainwater has a pH <5.5. Why is it called acid rain? Acid rain can have a harmful effect on the environment killing trees, polluting lakes and damaging buildings. How can the effects of acid rain be prevented? 1 of 20 27 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    28. 28. Contents 7E Acids and Alkalis What are acids and alkalis? Hazard symbols Indicators and the pH scale Neutralization Summary activities 1 of 20 28 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    29. 29. Glossary acid – A chemical that has a pH less than 7. alkali – A chemical that has a pH greater than 7 and dissolves in water. indicator – A special chemical that changes into different colours in acid and alkali solutions. neutral – A chemical with a pH of 7 that is not an acid or an alkali. neutralization – The chemical reaction between an acid and an alkali. pH scale – The range of values that shows how strong or weak an acid or alkali is. universal indicator – The indicator that shows the pH value of a chemical. 1 of 20 29 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    30. 30. Anagrams 1 of 20 30 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    31. 31. Word search 1 of 20 31 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    32. 32. Facts about acids  Weak acids, like lemon juice and vinegar, taste sour.  Strong acids are corrosive and can “eat away” at metal, stone and flesh!  Acids turns blue litmus paper red.  Acids have a pH of less than 7.  Acids can be neutralized with alkalis. 1 of 20 32 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    33. 33. Facts about alkalis  Alkalis feel soapy and are used in household cleaning materials.  Strong alkalis are caustic.  Alkalis turn red litmus paper blue.  Alkalis have a pH of more than 7.  Alkalis can be neutralized with acids. 1 of 20 33 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies
    34. 34. Multiple-choice quiz 1 of 20 34 of 34 © 2011 Excel © Boardworks Ltd 2004 Learning Technologies

    ×