Acids and Alkalis

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1. Chemistry Acids and Alkalis

2. Contents Acids and Alkalis Neutralization Summary activities What are acids and alkalis? Indicators and the pH scale

3. What is an acid? Acids are a group of chemicals that donate a proton in a reaction. What do you know about acids ? Are all acids dangerous?

4. What is an acid? everyday acids laboratory acids

5. What are acids? Acids are substances that: Have a pH below 7 and turn universal indicator yellow, orange or red.

6. Properties of acids An acid is a substance that releases hydrogen ions (H+) into an aqueous (water) solution. are corrosive. have a sour taste turn blue litmus paper red react with some metals, releasing hydrogen gas and leaving a salt behind conduct electricity are neutralized by bases, producing water and a salt.

7. What is a strong acid? Some acids, like those found in the laboratory or a car battery, dissolve completely in solution. They are very dangerous (too dangerous to taste or touch). These acids are said to be corrosive as they can damage other materials by eating them away! They are strong acids .

8. What is a weak acid? Many acids are found in household items such as food, drink and beauty/skincare products. These acids do not dissolve completely in solution and are known as weak acids .

9. Wear Safety Glasses!!!

10. What is an alkali? everyday alkalis laboratory alkalis Alkalis, or bases, are another group of chemicals, the opposite of acids.

11. A base is a substance that releases hydroxide ions (OH – ) in an aqueous solution. are caustic have a soapy, slimy feel turn red litmus paper blue have a bitter taste conduct electricity are neutralized by acids, producing water and a salt. Properties of Bases

12. What is a strong alkali? Some alkalis, like those in the laboratory or in cleaning materials such as toilet cleaner, dissolve completely in solution and 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, or bases .

13. 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 do not dissolve completely in solution and are known as weak alkalis, or weak bases .

14. Contents Acids and Alkalis Neutralization Summary activities What are acids and alkalis? Indicators and the pH scale

15. 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 color in an acid or an alkali. What is an indicator? Litmus paper and litmus solution are examples of indicators. Litmus is red in acid. Litmus is blue in alkali.

16. Litmus test experiment

17. 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. What is universal indicator? Universal indicator has a range of colors that show how weak or strong the acid or alkali is. stronger alkali stronger acid What is the color for a weak acid? What is the color for a strong alkali? weak alkali weakacid strongalkali neutral strongacid

18. The strength of an acid or alkali is measured by the pH scale . What is the pH scale? Each universal indicator color is given a number called the pH value . Universal indicator can tell you the pH of a solution. What is the pH of a weak acid? What is the pH of strong alkali? weak alkali weakacid strongalkali strongacid stronger alkali stronger acid neutral 1 2 3 4 5 6 7 8 9 10 11 12 13 14

19. What is the pH?

20. Are these substances acidic or alkaline? Are they weak or strong? 1 2 14 13 12 11 10 9 8 7 6 5 4 3 Substance pH Description of acid/alkali soda water 6 car battery acid 1 soap 8 washing soda 10 stomach acid 2 oven cleaner 14 vinegar 4 very weak acid very strong acid very weak alkali weak alkali strong acid very strong alkali weak acid alkali acid What type of substance?

21. Contents Acids and Alkalis Neutralization Summary activities What are acids and alkalis? Indicators and the pH scale

22. 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? ?

23. What is neutralization? The chemical reaction between an acid and an alkali is called neutralization . What happens to the pH value of the reaction mixture during neutralization? acid alkali a salt water The pH value of the reaction mixture becomes closer to 7.

24. What is neutralization? The chemical reaction between an acid and an alkali can be written as: What are the two new substances produced by a neutralization reaction? a salt acid alkali water

25. Neutralization and indigestion

26. Neutralizing stings A bee sting is acidic . A wasp sting is alkaline . Why can bicarbonate of soda ( pH 9 ) be used to treat a bee sting? Why can vinegar ( pH 3 ) be used to treat a wasp sting?

27. 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?

28. 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?

29. Contents Acids and Alkalis Neutralization Summary activities What are acids and alkalis? Indicators and the pH scale

30. 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.

31. Anagrams

32. Word search

33. 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. Facts about acids

34. 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. Facts about alkalis

35. Multiple-choice quiz

36. Guided Notes