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7E Acids and alkalis

7E Acids and alkalis. 7E Acids and alkalis. Acids and alkalis. Indicators. Neutralisation. 7E Acids and alkalis. Acids and alkalis. 7E Acids and alkalis - Where are they found?. 7E Acids and alkalis - Concentrated and dilute. concentrated acid. weak acid.

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7E Acids and alkalis

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  1. 7E Acids and alkalis 7E Acids and alkalis Acids and alkalis Indicators Neutralisation

  2. 7E Acids and alkalis Acids and alkalis

  3. 7E Acids and alkalis - Where are they found?

  4. 7E Acids and alkalis - Concentrated and dilute concentrated acid weak acid Compare the particle model of a concentrated acid with a weak acid. Which sentence best describes which acid? A. This acid has only a few acid particles compared to water particles. B. This acid has a lot of acid particles compared to water particles. Why is a dilute acid less hazardous than a concentrated acid?

  5. 7E Acids and alkalis - True or false? True or False? 6. The acid some people like to put on pancakes is called ethanoic acid. 1. The word acid comes from the Latin word “acere” meaning “sweet”. 2. The word “alkali” comes from the Arabic “al-qily” which means “plant ashes”. 3. All acids are dangerous and can burn skin. 4. Acids and alkalis that are dangerous to taste and touch are called caustic. 5. Pure water is not an acid or an alkali. FALSE! Only strong acids are dangerous. Weaker acids, like citric acid, are not harmful to skin. FALSE! Ethanoic acid is the chemical name for vinegar. Vinegar on pancakes - YUCK! Most people prefer citric acid in lemon juice. TRUE! Pure water is called neutral. In nature, rainwater is weakly acidic and seawater is weakly alkaline. TRUE! Arabic chemists used to make alkalis from the remains of plant ashes. FALSE! They are called corrosive. Dangerous alkalis are sometimes called caustic. FALSE! The Latin word “acere” means “sour”. Acids have a sour or bitter taste.

  6. 7E Acids and alkalis Indicators

  7. 7E Indicators - What is an indicator? Some chemicals have different colours in acid or alkaline solutions. These coloured chemicals are called indicators. Litmus indicator is a vegetable dye. Litmus is always blue in an alkali. Litmus is alwaysred in an acid. Litmus is purple in water. How can you tell if a solution is an acid or an alkali?

  8. 7E Indicators – Litmus test

  9. 7E Indicators – Universal and pH scale To tell the strength of an acid or alkali we need an accurate indicator called … Universal indicator is a mixture of several indicators. It shows the strength of acids and alkalis based on the… pH FACT: The pH scale was invented in 1909 by Soren Sorenson, a Danish chemist who was working on beer quality! How can you tell if an acid or alkali is weak or strong? universal indicator pHscale

  10. 7E Acids and alkalis Neutralisation

  11. 7E Neutralisation - What is neutralisation? alkali + universal indicator acid + universal indicator An acid has a pH less than 7. An alkali has a pH greater than 7. What happens to pH when an alkali is added to an acid?

  12. 7E Neutralisation - What is neutralisation? Mix an acid and an alkali together and a chemical reaction takes place. Why has the indicator turned green?

  13. 7E Neutralisation - What is neutralisation? If the right amounts of an acid and an alkali are added together the pH of the mixture changes to neutral (pH 7). acid + alkalineutral solution This reaction is neutralisation. What would happen to the pH value if more acid was added to the mixture? What would happen to the pH value if more alkali was added to the mixture?

  14. 7E Neutralisation - Using neutralisation Neutralisation can be a very useful reaction. Acidic problem Neutralising treatment 1. Indigestion caused by too much stomach acid A. Rub with leaves of alkaline plant 2. Acid rain pollutes lakes and poisons wildlife B. Regular brushing with alkaline toothpaste 3. Power stations produce gas which forms acid rain C. Antacid tablets D. Calcium carbonate neutralises acidic gas before it is released 4. Nettle sting contains acid which irritates skin 5. Mouth bacteria produce acid from sugary foods E. Calcium carbonate reduces acidity of water Match each problem with the correct neutralising treatment.

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