New Topic: Acids and Alkali LO: to list a number of household acids and the pH of numerous substances using pH paper Making your own Indicator to test everyday acids and alkalis 2 important types of solutions are acids and alkali’s Acids taste sour Alkali taste bitter We have also used many acids and alkalis in the lab this year. TASK: Make a list of all the acids and alkalis you have heard of before either in the lab or at home? Who can come up with the most?

5.1b Identifying acids and alkalis Alkalis are the chemical opposite of acids. They feel soapy. Washing powders dissolve in water to make alkaline solutions.

5.1b Identifying acids and alkalis You probably use one alkaline substance every day – toothpaste. Toothpaste helps protect teeth against acid erosion.

5.1b Identifying acids and alkalis Sodium hydroxide is an important alkali. Companies use huge amounts of it to make paper, detergents and aluminium for fizzy drinks cans.

Particle models of a concentrated acid and a weak acid. 7E Acids and alkalis - Concentrated and dilute Particle models of a concentrated acid and a weak acid. concentrated acid 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? A dilute acid is less dangerous than a concentrated acid because there are less acids particles in a dilute acid.

Discuss these questions with your partner Discuss these questions with your partner. Be ready to feedback your ideas to the class What is a strong acid? What is the keyword for strong acids? What is the opposite of a strong acid? What is the keyword for weak acids? How can make a strong acid weak? How can you make a weak acid strong? What does adding water to an acid do? Time: 5 min

Range of colours, tell us how strong acid or alkali is Indicators An indicator is a dye which changes colour according to whether it is in an acidic or alkaline solution. For example, universal indicator Range of colours, tell us how strong acid or alkali is 1 2 14 13 12 11 10 9 8 7 6 5 4 3 Strong acid Neutral Strong alkali Weak acid Weak alkali pH scale

Making your own Indicator Apparatus Pestle and mortar Filter paper and a filter funnel Red cabbage leaves Boiling tube or conical flask Hot water Method 1 Put some red cabbage leaves into the mortar. 2 Add a little hot water. 3 Grind up the leaves so that you get as much of the colour out as possible. 4 Filter the mixture and collect the liquid in a tube or flask.

universal indicator demo In your books, explain what I did and why the universal indicator changed colour

Practical: Safety with acids http://uk.youtube.com/watch?v=s0CyLbiwHkg How should spilled acids be cleaned up?

Part 2: Using your indicator Apparatus •Red cabbage juice Dropping pipette •Spotting tile Substances to test

Investigating the pH of everyday substances Copy the title and table into your book, then go around the class and test the everyday substances to see if they are acids, alkalis or neutral Investigating the pH of everyday substances You will need the following results table: Substance Colour with red cabbage indicator Colour of pH paper and pH number Acid/Alkali or neutral Strong or weak METHOD Wear goggles and tie hair back In your groups, put a few drops of each substance in the white tray. Note down the name of each and your observations in the table. Put a piece of indicator paper in the substance and record what colour it goes.

7E Acids and alkalis - Where are they found?

7E Acids and alkalis - True or false? 6. The acid some people like to put on pancakes is called ethanoic acid. 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. 1. The word acid comes from the Latin word “acere” meaning “sweet”. 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! Arabic chemists used to make alkalis from the remains of plant ashes.   TRUE! Pure water is called neutral. In nature, rainwater is weakly acidic and seawater is weakly alkaline. 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.  

Assessment feedback Homework: Revise for Elements, compounds and mixtures test

Plenary learning log

Hazard!

Hazard!

Hazard!

Hazard Symbols

Hazard Symbols

Hazard symbols What are hazard symbols? What are they used for? What colour are their background? Why do we use them? What are the advantages of using them instead of words?

Homework Produce a leaflet on a famous scientist Note when and where they were born What were they famous for What books or papers did they write Why was their work important? Any other interesting facts about them and their work Remember No CUT AND PASTE and make sure you understand everything you write

Post it notes 2 post notes On one, write 3 things you have liked the most about science last term On the other write down some things that you think could be better Stick them on the board on your way out

Repro test

Combustion demo Write down your observations in your book Why did the money not burn?

Methane bubbles demo Write down any obserations in your book? Why did the bubbles rise?