Year 10 Cooling by evaporation - why does hand sanitiser feel cold?

Look at this photograph of the ball bearing model of Kinetic Theory. Kinetic Theory says that all atoms are always moving. But look carefully at the ball bearings in the photograph. Most of them are at the bottom. They have low energy. A few are at the top because they have high energy. In fact, one or two had so much energy that they jumped out of the tube.
Now, the kinetic energy of atoms tells you the temperature. High kinetic energy = high temperature. Low kinetic energy = low temperature. If the high energy atoms jump out, then what is left are the low energy atoms. High energy atoms jumping out is called EVAPORATION. If you put hand sanitiser onto your hands, it evaporates. the high energy atoms jump out into the air leaving the low energy atoms behind. Low energy = low temperature. Hand sanitiser feels cold.

Year 10 Air pressure and kinetic theory experiment

 We started with a can full of air and with a small amount of water in the bottom. We heated the water until it boiled. Steam was coming out of the top of the can and it pushed the air out of the can. So now we had a can full of steam.

Next we very quickly tipped the can upside down into cold water. The cold water made the steam condense and turn back into water. Water doesn't take up as much space as liquid water so now most of the inside of the can was an empty space - a VACUUM. The air particles outside hitting the can and causing pressure (kinetic theory) crushed the can because there were no air particles inside the can pushing outwards to stop it crushing.

Year 10 Kinetic Theory and Pressure

We saw this model of atoms in the air. The tiny metal ball bearings are like the atoms and they are constantly moving at high speed. The fact that atoms are always moving is called KINETIC THEORY. In the picture above, the atoms crash at high speed into the polystyrene block. This pushes the block up. Pressure in the air exists because atoms in the air are crashing into objects at high speed all the time.

What happened when Isaac Newton was self-isolating

Here's a picture of Isaac Newton's famous apple tree from his home at Woolsthorpe, in the countryside near Grantham. When the plague hit Cambridge, the university students were sent home. He did his best work there. I'm working out how we can do some home experiments during this time. https://www.washingtonpost.com/history/2020/03/12/during-pandemic-isaac-newton-had-work-home-too-he-used-time-wisely/

Marie Curie book

This month's Wigton Library Book Club has been "Marie Curie and her Daughters" by Shelley Emling. It deals with the second half of Marie Curie's life, starting on 1911 with her second Nobel Prize for Physics. It was written by an American author and deals therefore with the American angle on the Curie family story. I did once see a documentary about this - about how a friendship with an American journalist led to American charity donations funding Marie Curie's research institute. One thing that I really admire about Marie Curie is that she believed obstinately in research being made freely available so she never patented her work. The other thing I took from the book is that I have long neglected the work of her daughter and son-in-law who were awarded the Nobel Prize as well for discovering artificial radioactivity - when bombarding an unradioactive element makes it then become radioactive.

Paul Dirac on In Our Time

Well, not in person. He was the subject https://www.bbc.co.uk/programmes/m000fw0p

Range and resolution in the Victorian kitchen at Penryn Castle

This lovely spring balance has a range up to 200 lb. I'll call that a Full Scale Deflection like I would for an analogue ammeter because the needle is actually deflected. The resolution is usually taught to be the smallest scale division: in this case +/- 1 lb. But this is a single point measurement so +/- 0.5 lb would be better. For a ruler where it is being lined up at either end, the +/- 0.5 divisions error at each end then gives you the +/- 1 scale division resolution.