 The use of fossil fuels is releasing greenhouse gases into the atmosphere, raising their concentrations, in particular carbon dioxide. Now that carbon dioxide in turn can dissolve in the oceans, making them more acidic. That's a process called ocean acidification. Sea life, anything from plankton to mollus, indeed the whole food chain can be affected by ocean acidification. In this lesson we're going to explore how carbon dioxide increases acidity, and how that increase in acidity can affect marine life, in particular living things with calcium carbonate exoskeletons or shells. How are we going to demonstrate the concept of ocean acidification? OK, so we're going to do it through three experiments. All the experiments are linked. So we first find out what carbon dioxide does to the water. We then look at what a seashell in that type of environment is going to produce, the carbon dioxide bubbling. And then if they're exposed for any length of time to it, how that is going to affect those organisms. For the first experiment, you need salt water. Each group needs two beakers or cups, one lid, two straws, a pH meter or universal indicator, and a stopwatch. For the second part, we need salt water plus household vinegar. Two cups or beakers, one shell that has been soaked in vinegar for two days and three shells that haven't been soaked. Each group will need a stopwatch and some one kilogram masses. The first experiment we're going to be looking at the effects of carbon dioxide in sea water. The first thing they'll be doing is putting their straw into the sea water through the lid, and they're blowing continuously. After 30 seconds, they take the actual pH of the solution. So they're investigating it with a lid or without a lid. So we're looking for a change of pH from slightly alkaline to slightly acidic. As more carbon dioxide is produced, more carbon dioxide is dissolved into the ocean and therefore it tends to move more towards the acidic range on the pH scale. If you've got pH meters, by all means try them, maybe do a comparison between those and the universal indicator, or just do the universal indicator. How does the lesson then progress? Now what we need to do is we need to get a couple of beakers again. Same size beaker, small preferably. We're going to make a couple of solutions up. One which is about 30 centimetres cubed of sea water and then 30 centimetres cubed vinegar. It doesn't have to be that quantity, so long as it's a half and half mix. And then in the other beaker, we have the same volume but just vinegar. What this is to do is this is to see what the effect of an acidic environment would have on a sea shell. When we place the shells in them, we would see a difference in the number of bubbles produced in the full acid compared to the half and half solution. The students will write down their observations of what they see. And then can you substitute anything for shells? Yeah, you can. You don't have to use shells from the beach and when we're lucky we live by the seaside but you can use eggshells as well or anything with some form of calcium carbonate in it. We can now look at the effect of acidification on the strength of shells. We then take a shell that has already been exposed to an acidic environment. What we do with these shells is we soak them in vinegar for about 48 hours. Then we move on and we take a cardboard guide tube, we place that in the centre of that and then it's a case of every 15 seconds or so. You could do it less than that or more than that if you wish. You place a weight, a mass on top of the shell and just make sure that that is in that guide tube. And then you wait a certain amount of time just in case you hear any crack in or any split on it. Any health and safety configuration. There's plenty of health and safety considerations. Not only are we worried about the masses falling off the table but we're also worried about trap fingers underneath them as well. And it's important that students don't drop them onto the shell. They place them gently and as I say if you have it facing inwards on the table like you have then we've got less chance of them falling off. So today we're going to be doing an experiment to, we're going to take salt water, so sea water and we're going to add carbon dioxide to it and you're going to do that by breathing into it and we're going to see how that changes the acidity of the sea water and then afterwards we're going to see how that change in acidity affects marine life. Now all the stuff we're using today has some form of irritation in it and we don't want it on our bodies or in our eyes so we will all be wearing goggles. Okay so we've got two beakers with 60 centimetres cubed in of sea water. You're then going to place a lid on one of them which is a tin foil. Using the sharp pencil I put on your desk you're going to place a hole in there because that's where your straw is going to go and then place a second hole because that's where the pH probe is going to be able to go. Okay so I take a deep breath, I hold it for a few seconds and then I start blowing. On that 30 seconds you stop breathing into it, a little stir with the pH probe, okay and then let it and then you should take the reading off the pH meter, place it into your table. You then do the same thing again for another 30 seconds. You continue this for two minutes. After two minutes you stop. You need to be very careful when you are blowing through this straw because it will bubble and come up over the side okay. Do we have to measure zero seconds before we start? Absolutely yes, we do measure at zero because we need a base point for what our solution is at in terms of pH. Right remember, blow, do not suck okay. You will not want to get this water in your mouth okay. So just be aware of that okay and don't blow too hard. One, stop. How long is that? What does it say? 6.57. What did we see with no lid and then with lid? No lid started quite high and then it made its way down but then it went back up again and with a lid it started high and then made its way down. What do we think the lid has done then? It might have trapped some of the gas. It has trapped some of the gas in there hasn't it? Okay so what we are looking at now is the effect of that slightly more acidic seawater on living things like seashells which have calcium carbonate in their exoskeleton. On your desk you should have two beakers. You are going to take seawater and in the first beaker you are going to put that up to 30 and then you are going to add 30 vinegar. Okay it is white vinegar. And in the second beaker you are going to do 60 vinegar. It is a very easy experiment in this one. If you spill that on yourselves you will smell like a chip shop all day so just be aware of that. We are now going to take the two of the three shells. What you are going to do is you are going to place them both at the same time in the beaker and you are going to write down some observations. So does anybody have any predictions what is going to happen? So one shell is in the full vinegar and the other shell is in the half seawater, half vinegar. The shell in the vinegar will dissolve quicker or break down quicker because the vinegar is more acidic. So it is one more obvious than the other one? The full vinegar one is more bubbly compared to the more down one. The water is going more like grain. We are now looking at the long term effect of those same organisms that have been subjected to an acidified ocean. We are going to look at the effect that could have on their shells. So this is kind of a strength test. The way we are going to do that is you have got a shell on its own in your little dish here. It will look really white because these have already been subjected to acid conditions. You are comparing that against the other shell you had left which you will notice the difference in them if you look at it. Observation wise you will notice there is a difference in between them. One of them has still got colours on the outside of it and the other one is like a white kind of chalky effect on there. Now the way we are going to do this is set back on your table because health and safety we need to think about that still. We are going to place our shell within the guide tube and what you are going to do is you are going to be placing the masses on top of it carefully. You are going to wait. Now you can set a timer for this. What we are looking at is any weakness in the structure of those shells caused by an acidified environment. A little bit more worn away. We will see if that changes anything. I think I had a crack there. Yeah, that is cool. Right, take them off. Can you hear anything? Yeah, roofs caved in. Yeah, caved in after about four. OK, next one. I was surprised it would break completely because it felt really weak. Yeah. Thank you. I am just going to hold it because... Hey! It is interesting. We talked about it, didn't we? What effect it will have. Of course it is not going to produce organisms that just shatter. That is not what happens. But it will result, we think, in organisms that are smaller and more brittle. And so it will change the balance of life in the ocean. We have got to remember that we are not saying that the oceans are acidic. They are not acidic. What we are getting is a slight increase in acidity. If we look at it on a pH scale, we still cannot call it an acidic ocean. All we can say is the acidity is increasing slightly. I suppose there are lots of connections between these simple experimental results that you can demonstrate in the classroom and much wider global issues. So most people know about the rising levels of CO2, but they don't necessarily link that into things like coal bleaching and the habitats that that destroys. It is this type of activity is more accessible to the students and by doing a practical it kind of puts an idea into the head of, oh, hang on, this is happening because they are actually hands on and seeing it happen. Reading it in their newspaper or hearing it on the news because they are not physically doing it. They tend to not make those links. I thought this lesson was wonderful. I think the students really enjoyed it because it was very visual. They could see this change in acidity, ocean acidification and with the shells they could see the link between that process and climate change.