DIY Ice Cores: A Hands-On Climate Change Lab
One of the most challenging things about teaching Climate Change is helping students to understand the evidence we have for this alarming phenomenon…how can we know that the changes that are happening on Earth now are not just a natural shift in Earth’s climate? After all, CO2 sensors have only existed since the 1960s (NASA has some excellent articles about the development of gas sensor technologies), so how can we say that the change is problematic after only 60 years? The answer is proxy data, data that gives us indirect measurements of past environmental or climate factors from long ago. Some common examples include tree rings (for temperature and precipitation patterns), ice cores (for atmospheric conditions, Greenhouse gas (GHG) concentration & temperature) as well as layers of sediment. The oldest ice sheets in Antarctica can give us data from up to 800,000 years ago while younger ice in Greenland gives us data from up to about 120,000 years ago. Therefore, this proxy data source is key in our understanding of the long-term climatic patterns of our planet.
As a science teacher I am constantly working to find ways to help my students further develop their lab skills, using tools like mass balances correctly (that darn tare button), measuring the volumes of liquids and other basic skills that students need to have mastered before they move on to more advanced courses like the IB Diploma or AP Sciences. So, when I found this lab at an AP Environmental Science teacher workshop (modified from the Wisconsin Department of Natural Resources) I knew I had science teacher gold! This lab is an excellent way to practice those fundamental skills and connects directly to key understandings when teaching students about climate change.
Lab skills students will use in this lab:
Using a hot plate & working with hot glassware safely
Measuring the volume of a liquid with a graduated cylinder
Measuring mass using an electronic balance (taring/zeroing the balance)
Considering the mass of the container when measuring the mass of a substance
Calculating ice density using their measured masses and volumes
Calculating concentration using mass of particulates and volume
Measuring pH using pH paper or probes
Following a laboratory procedure correctly (in this lab you need to follow the steps in order or you will be unable to collect the data)
Since this lab includes a variety of steps, tools and requires a level of lab skills that not every student will have I make sure to set up my laboratory word wall with all the necessary equipment ahead of time. I also hand out the procedure the class before the lab and make reading the lab as well as making predictions the student’s homework. This ensures that most students have read over the procedure (download it for free below) and hopefully they will be better prepared and I will have less questions to answer during the lab. Finally, depending on the class, I spend some time reviewing key lab skills such as measuring the volume of a liquid (use a graduated cylinder not a beaker & measure from the bottom of the meniscus) and how to use the mass balance correctly (patience with the buttons, tare or zero gives you the mass of anything you add to the container & measure empty containers before you begin and don’t assume that all 150 ml beakers have the same mass!).
The most challenging part of this lab is the prep, it takes about a week to make all of the ice cores, adding one layer in the morning and one at the end of the day (as long as I have time) to each plastic graduated cylinder. My poor Science colleagues know that I’m doing ice cores when the freezer is emptied out and then full of 100 ml plastic graduated cylinders for about 1.5 weeks. It took us a couple of years to buy enough plastic graduated cylinders to do this lab, so if you are like me and you have multiple classes doing the same content you can always stagger the lab if you are short on graduated cylinders.
Here is the ice core building process:
Materials:
one plastic 100 ml graduated cylinder per group of 2 or 3 students
freezer space, the cores need to stand upright to freeze
food colouring (I use different shades & combinations of red, blue and yellow to make each layer a different colour)
about 50 ml of sand, small rocks, ground up cat litter and other sediments
the ash from 2 pieces of paper or about 100 ml of ash from a fireplace
one large bottle of carbonated water, since this process takes several days if you need more for a large class you can pick some up
Procedure:
Clean all the graduated cylinders and make sure they fit in your freezer
Prepare your first layer, I do 8 layers, but you can use less if you like
In some layers you will add some different particulates, use a mix of carbonated water and tap water to change the pH and use food colouring to help make the layers more visible to your students
They key is to make your layers more acidic at the top of the column as this will help them notice a trend in dissolved CO2 – so start with a layer of just tap water then add more and more carbonated water each time (see the table below for an example)
The solids are meant to represent debris from volcanic eruptions as well as pollution, so they can be added at different layers as you so choose, I recommend you measure the pH as you go for your answer key and to make sure it is getting more acidic as you move up the ice core
Do not add any new layers until the previous ones are completely frozen, students will need to separate them in the lab and this is much easier if they haven’t mixed together
Here is a sample of how I add my layers when I do 8 layers, I usually make 25 ice cores at once, so if each layer is about 10 ml I need to make 250 ml of each layer mixture to add:
Layer | Water Mix | Sediments to Add | Food Colouring |
#1 (oldest) | 100% (250 ml) tap water | None | Orange |
100 % (250 ml) tap water | Ash for a volcanic eruption | Blue | |
10 % (25 ml) carbonated water, 90% (225 ml) tap water | None | Red | |
25% (63 ml) carbonated water, 75% (187 ml) tap water | Small bits of sand for sandstorm in the wind | Green | |
50% (125 ml) carbonated water, 50% (125 ml) tap water | None | Light blue | |
75% (188 ml) carbonated water, 25% (62 ml) tap water | None | Purple | |
80% (200 ml carbonated water, 20% (50 ml) tap water | Small kitty litter particles for pollution (small amount) | Yellow | |
90% (225 ml) carbonated water, 10% (25 ml) tap water | Small kitty litter particles for pollution (large amount) | Clear (no food colouring) |
Now that your ice cores are made and your students have the lab sheets set its time to have fun in the lab! I rarely make this lab a graded assessment as I have found that students’ results often vary significantly for a variety of reasons and instead I incorporate it into their unit test. Here are some tips to help make this lab day run more smoothly:
Have a couple of kettles of boiling water ready, use these to extract the ice cores from the graduated cylinders by pouring a small amount of the hot water along the outside of the graduated cylinder, just enough to loosen the ice core without melting it all
Give each group a cutting board with a little groove around the outside so that they can keep their ice core safe and separate the layers more easily with the help of a butter knife
Have students use tape or a glassware marker to carefully label each beaker so that they can keep the layers separate and write the mass of each empty beaker directly on the tape
Make sure students don’t lose too much of their ice when melting it on the hot plate by keeping the temperature relatively low
When trying to evaporate all of the water be aware of splashes, you will soon have a food colouring covered lab bench if students keep the hot plate too hot as some may do as they rush to finish the lab
Make sure students know to put hot glassware from the hot plate onto a cork board or something similar and not directly onto a cold surface, while laboratory glassware is quite sturdy a sudden change in temperature could cause it to crack
I hope you find this useful and enjoy this lab with your students, it is one of my favourites! Thanks for reading, teachers, travelers and curious souls of all kinds.
The Roaming Scientist
