Dr. Bob discussed the overwhelming evidence that the climate is changing and that human-driven fossil fuel burning is is the primary cause of the sudden climate change we are observing. To see how straight-forward is this conclusion, he and his guests performed seven experiments in this debut Family Science Night performance. Here he explains some of the experiments he tried at home and on the show (with appropriate supervision, of course.)
Is CO2 a greenhouse gas?
In this experiment, we heated two identical globes in two identical glass containers with two identical glass lids. One can put any object inside the glass container to absorb the short waves of the heat lamp so long as it leaves space for the gas. I filled the airspace of one container with CO2 by pouring 200 mls (a little less than a cup) of vinegar into a 2 L soda bottle that contained 1 Tbsp of baking soda, then I poured the gas (not the liquid) into the glass container with the globe. I carefully turned on a heat lamp to shine on the two globes and we measured the temperature in the containers over time. The CO2-filled container warms faster partly due to greenhouse effect (and probably partly due to heat capacity). If a container with CO2 does not warm faster, maybe it is farther from the lamp than the air-filled container. I tried using the same container at the same distance from the lamp for each gas and this worked well. And I had to repeat the experiment for sure!
Heat capacity of water - the flame-proof balloon!
90% of the heat we are adding to the atmosphere is going into the oceans. Why? Because water has a high "heat capacity." That means it can absorb a lot of heat without itself changing temperature very quickly. We demonstrated this fact by inflating two identical balloons to the same size - one filled with air and one with water. CAREFULLY (with grown-up supervision and safety glasses) we held the air-filled balloon over the flame of a lighter, and in no time, POP! Next, we tried holding a flame under a water balloon, and although the flame burned and burned for more than a minute until the balloon was charred, the balloon did not pop! The heat went straight through the rubber and was absorbed by the water!
Water expands as it warms.
The heat we are putting into the oceans is slowly warming the oceans. Even if land-based ice were not melting to add water to the oceans (which it is), the warming of the oceans would still lead to sea-level rise because warm water takes up more volume than the same amount of cool water. We demonstrated this by warming water in a container with a narrow neck. Any narrow-necked container showed me the same effect. I just had to fill the container to the neck with water, mark the water level on the neck, warm the water somehow (like in a microwave) and then check its depth compared to the mark I put on when it was cold. The evidence shows that most of the sea level rise we are already seeing is due to ocean expansion. Any land-based ice that melts (think Greenland and Antarctica) makes sea levels rise even faster.
The oceans are not just warming and expanding, they are acidifying.
We did an experiment with purple pH indicator showing that CO2 shaken into water makes the water more acidic. This happens because CO2 dissolves readily in water to make carbonic acid. We showed how bad this would be for shell-making sea creatures by comparing what happened to little bits of seashell dropped into test tubes of water with ones dropped into test tubes of vinegar. The vinegar dissolved the shells quickly! Calcium carbonate shells (like those of snails, clams, and sea urchins) become harder and harder to assemble as the acidity of the oceans rises. This experiment is also possible with chicken egg shells and vinegar.
What gives water such seemingly magical properties? Why were these properties essential to the formation of life? How can this humble molecule be at both fickle and unstoppable? Come hear the evidence, try some experiments, and judge for yourself! This second Family Science Night of 2018 will include demonstrations, activities, and a whole lot of fun science geared to teens, tweens, and their families.
Check back to see the summary after the show.