We've started a new topic for 4 credits at the end of Term 3! And depending on how hard we work, we could even do ANOTHER 4 credits in Term 4! On Thursday we started looking at different types of metals, making observations, and we weighed 1 cm cubed samples of them.
Then yesterday we graphed their density (g/cm3) before learning what density actually is - the amount of particles packed into a given area. Objects or liquids that are more dense have more particles packed into the same volume.
First we watched this video.
Next I revealed to students the list of the liquids available to them and gave them each a piece of paper with two blank test-tubes drawn on it. Students got to draft a density tower that they thought would be most accurate, and then have a second guess by drawing a second test tube with some of the orders of liquids changed around.
The liquids we used were:
water (pink food colouring)
dishwashing liquid (green)
olive oil (yellow)
water + corn starch (bright red, lots of food colouring)
golden syrup (golden)
soy sauce (brown)
baby shampoo (yellow)
I quite liked this activity because there was a lot of discovery learning happening. I didn't know the exact order in advance, and there were a lot of questions being thrown around like "is soy sauce going to sink through water?" which I got to answer with "I don't know, go and get a test tube and find out before you add it to your density tower." There was also some logical thinking happening, like when Duui decided that dishwashing liquid would be more dense than water because when he uses it at home it moves to the bottom of the sink, and Brandon had a think about oil spills and water.
I discovered that soy sauce is more dense than dishwashing liquid, because it sank right through the dishwashing liquid in my tower and sat on top of the conditioner layer.
Most students guessed that the golden syrup would be the most dense.
Here are some photos from our class:
Mac, David and Duui gently adding the next layer to their beakers.
Mac's first attempt
Students working and cleaning out their beakers after failed attempts. It was quite good to get it wrong and have a layer sink through, because then they knew to add it earlier as it was more dense.
Mac's best "scientist face" as he studies his density tower - many more layers this time!
I think that this lesson (messy, loud, and a little silly) was a good one to illustrate density.
Next week we'll have to start thinking about why cars and planes might be best made from more or less dense metals.. hmm...