Material changes, Acids, AlKali, neutralization reaction

Explore the fascinating world of material changes with this presentation! We'll delve into the properties of acids and alkalis (also known as bases), unraveling the science behind their surprising effects.

1. Unit 7: Material changes

2. Table of contents 7.1 7.3 7.2 7.4 Acid & Alkalis Is it an acid or an alkali The pH scale Neutralisation 7.5 7.6 Neutralisation in action Investigations acids and alkali

3. Whoa! This can be the part of the presentation where you introduce yourself, write your email…

4. Acids and Alkalis 7.1

5. Many thing contain acids. Some foods contain acids. They have sour, sharp, tangy taste. Common acids in laboratory are hydrochloric acid, sulfuric acid and nitric acid. When acids mix with metals or carbonate rocks, they can cause a fizzing or bubbling reaction. Acids are everywhere Some acids are strong. They are corrosive . If a strong acid gets on your skin, you will get a chemical burn. Acids can be diluted with water, this makes them less dangerous. Some acids are dangerous

6. An alkali is a substance that can neutralize an acid, often having a slippery or soapy feel, and a bitter taste. Examples of alkalis include substances like baking soda and certain cleaning agents. When diluted with water, they become less dangerous. Common alkalis are sodium hydroxides, potassium hydroxides and calcium hydroxides. Alkalis are everywhere Stand up to work. Wear safety glasses Take the top off the bottle and place it upside down on the work surface. Replace the bottle top as soon as you finish using the bottle. Work safely with acids & alkalis Do question answers of topic 7.1 (page # 90, 91) on your nb.

7. Properties of acids and alkalis Acids Alkalis Corrosive corrosive Sticky to touch Slippery/soapy touch Sour taste Bitter taste Smell (can burn the nose) Usually no smell Acids turn blue litmus red Turn red litmus blue pH less than 7 pH more than 7 React with alkali to form salt and water React with acid to form salt and water Conduct electricity Conduct electricity Calcium hydroxide solution, commonly known as lime water, is used to test for carbon dioxide. When the gas is bubbled through lime water, it turns milky.

8. Is it an acid or alkali 7.2

9. An indicator is a dye that changes color when it is put into an acid or an alkali and shows whether a solution is acid or alkali. Indicators Litmus is an indicator ; it is a blue/purple die which comes from small plants called lichens. Litmus paper is a quick way to identify an acid or an alkali. Blue litmus paper is used to test an acid. It turns from blue to red , indicating acid. Red litmus paper is used to test an alkali. Red litmus paper turns blue in an alkali solution. Litmus

10. The pH scale 7.3

11. Universal indicator Universal indicator shows how acidic or alkaline a substance is. Type of substances Color of universal indicator Strongly acidic Weakly acidic Neutral Weakly alkaline Strongly alkaline

12. Neutralisation 7.4

13. Neutralisation When an acid and an alkali are mixed together they cancel each other out or neutrali z e each other. The diagram shows what happens when an acid is added to an alkali with universal indicator in it. At the start, before an acid is added, the indicator is purple. A s the drops of acids are added, the alkali is slowly cancelled out. T his causes the indicator to change color gradually. Eventually it becomes green – the solution is neutral.

14. Neutralisation in action 7.5

15. Your stomach produces hydrochloric acid. This gives the stomach the right conditions to digest your food. When your stomach produces too much acid you have indigestion. Alkalis are used to tread indigestion. The neutralizes the acids. They are also called antiacids. The bacteria in our mouth produces acid when they feed on the food particles left on your teeth. This acid damages your teeth and makes them decay. Toothpastes contain alkali and this helps to neutralize the acid. Indigestion Toothpaste

16. Investigation acids and alkalis 7.6