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ACIDS Vs ALKALIS
Chemistry Part 1
* start by welcoming them back
* repeat the rules of the club: if necessary play again the rules animation
* choose two assistant dearests with the swap and stop method
* award points to each team of two or three as you see fit
* Recap last week's class contents
1) a solid (either in one piece or in powder forms) and a liquid can react and the reaction can generate gases. Do you remember how we proved it? (A: WE used lemon juice and baking soda and we poured them in an empty film canister. The gas, wanted to be free and pushed the canister up in the sky, producing a little rocket)
and
2) if we use a reactant which takes up more space, the chemical reaction goes faster and can be more dramatic. Do you remember how we proved that?
(WE first poured water in the canister with a whole vitamin c tablet - the chemical reaction too 15'' or more
when we ground a tablet and added it to the water, the chemical reaction took a few seconds and was more dramatic - the rocket reached the sky. That's because the ground tablet takes more space than the unbroken tablet)
STEP 1: Today's adventure is: acids and bases/alkalis
Acids and bases/alkalis are all around us:
understanding acids and alkalis not only helps you understand chemistry but it also helps you understand the world around you
FOR SENIOR CLASSES ONLY:
* it also helps you understand the challenges we face: have you heard that oceans are becoming more acidic because of pollution? It's bad news because they should be alkaline. How can you FIND A SOLUTION TO THIS DISASTER if you don't understand the problem in the first place? You can only understand the problem if you understand acids and bases/alkalis
STEP 2: The pH scale helps us understand if something is an acid or an alkali. How?
How do you know how tall you are? You don't just feel it, you don't just decide, you measure yourself. That's what pH does; it measures if something is acidic or alkaline
STEP 3: the interesting part is that you can detect the pH of a substance in WATER or to use the proper term; ' in aqueous solutions' . Aqua is Latin for 'water'.
STEP 3: ANY pH value between 0 and under 7 is an ACID
7 IS NEUTRAL
ANY PH VALUE between over 7 and 14 is a BASE/ALKALI
Curiosity corner:
the LOWER the number between 0 and 6, the STRONGER the acid BUT the higher the number between 8 and 14 is STRONGER the base/alkali.
For example: pH 2 is a strong acid but ph8 is a weak base. A pH value of 12 shows a strong alkali.
Now let's play ACIDS Vs ALKALI
split the teams in two groups and let them line up (single file)
Get the assistants to take a position in the middle of the classroom (if you have outdoors space, do this out of the classroom)
one assistant represents acids, the other bases/alkalis
Now say a pH number between 0 and 14.
if it is a value between 0 and 6 the child at the top of the queu should run to the assistant that represents acids, (gently) fist bump her/him and then sit down on the side. If the number is 7, the participant needs to run between the two assistants and spin, id the ph value is between 8 and 14, the child needs to run to the assistant who represents alkalis and gently fist bump her/him
Step 4: now go to each team and fill one of the small cup with an acid of your choice (e.g.: vinegar) and one with al alkali of your choice (e.g.: water and washing up liquid) and use a litmus paper and the mini pH scale attached to each litmus paper wallet. Get them to compare and contrast colours with numbers and ask them what each number means. For example; if you get bright red it' usually a pH 2. WHAT IS A pH2? It's an acid
