Does coffee cool down faster than tea?

Kia ora koutou
Today I was playing with a supposition that I've had for a wee while, so I carried out a wee experiment with Anne looking on (she was in the midst of trying to eat lunch!). As we chatted and I gathered data, we ended up realising this could be quite an interesting one to share, about the process of our thinking, etc.
I had always thought that when I made myself a cup of tea (regular tea with milk), it always stayed hotter than if I made myself a jarrah coffee that doesn't have milk). These were my noticings, my observations. So today, I set up an experiment with a mug of hot water (for the pre-mix coffee) and a mug of hot water with some milk in (representing the tea). Now, I didn't write this up using a scientific method, this was the exploration period or, as Anne called it, the play. In my PLD sessions with teachers, I often talk about the benefit of letting students do the same experiment twice. There may be a few differences but the first session is the chance for students to have an explore, ask questions, and develop some thinking whilst the second session will build on this and perhaps have a more scientific bent, for example, we better measure the amount of milk carefully or we need to record how many stirs of the spoon.

The initial experiment. The feijoa is just an innocent bystander in all this. 

I recorded the data, a little haphazardly, and then we talked about what I had found out, whether what we were thinking was happening and where to from here. I found that as I did the 'play', I was starting to think more carefully about measuring, about other ideas to try out and what to do with the data. I also found out that my prediction that the hot water and milk mix would cool down at a slower rate wasn't really being reflected in my initial data. As more people tried to eat lunch (with one very concerned that her coffee would end up being experimented on), they started posing questions and wonderings too -the main one being about the milk and it's fat content, with the fat possibly retaining the heat, and how could we check that? We were discussing why the data might be reflecting certain results. Noone used google, we were just chatting about what might be happening.

Version Two!

I tried the experiment again with actual tea and jarrah coffee (and yes, I'm not sure why I didn't start with that either!) and again measured the temperatures of the two liquids. I tried to make them the same way I normally would and that threw up questions -you stir the coffee a lot more than the tea and did you add the same amount of milk to the first cup?
At the end, we talked about the data I had gathered and critiqued some of the recordings. Had I made sure it was exactly every 30 seconds? No, but reasonably close (and is that good enough?). How will you show the data -bar graph or line graph? Bar graph but you could use a line graph as it is measuring time... (which I ended up doing as well!)

 Because I started thinking about this as a science experiment and an opportunity to get critiquing happening, I decided to leave it a little messy... Is the line graph clear enough? Does it need more information? Do children know how to read a line graph and summarise what they can see? Do they understand the function of all the parts of the graph -the table, axis, etc... and now we have maths happening!
Wrapping this all up, we discovered that our initial results seemed to suggest that tea was getting colder faster and that it was all in my head. You can see I'm using tentative language as we haven't tried all the variables -was it the amount of stirring, the type of milk, the coffee powder itself, etc. We needed to have this preliminary activity to start our thinking, to begin to consider the variables at play and develop more wonderings from this. I like the idea of sharing the data with students and perhaps the graph and getting them to critique what I had done -was it scientific enough? Does it matter about the anomalies? From here, I might choose to experiment with a bit more purpose and in a more scientific way, ensuring that the procedure could be replicated by others.
This science idea came from my own wonderings, which I'm hoping we all have... why does tea slop in the cup when I'm walking along or the suitcase wheel around madly when I'm rushing to the terminal at the airport...
What are your wonderings?

Have a great term break, and see some of you next term!

PS, I'm on Facebook... look for science happening NZ and you should find me... I hope! If not, sing out because it means I've done something wrong!