DP1&2 Fun With Liquid Nitrogen

Background

Heating and cooling substance may bring about one or more physical changes in a substance as a result of a change in the energy content of the particles the substance is made up of. The particular changes in energy of a particle in the sample of substance may be either kinetic or potential energy or both. Kinetic and potential energy of a particle is a function of its motion and position relative to the other particles surrounding it. Energy change (whether kinetic and/or potential) in the particles of a sample of substance is accompanied by changes in Entropy as a whole. Regardless of the change, changes in the motion of particles can be at times be dramatically demonstrated.

Resources:
M4 Chemistry Matter II: State and Energy. PowerPoint slides on the relationship between state of matter and energy content of particles in a sample of the matter.

Discrepant Event

The video below shows three different demonstrations looking at the effect of cooling a squash ball, a rose and a small balloon filled with air using liquid nitrogen. Watch the video to see what happens.

And the questions are:

  1. Why did the squash ball and the rose shatter like glass?
  2. Why did the balloon deflate when introduced into liquid nitrogen and then spontaneously re-inflate when taken out?

Concepts involved:

  • cooling, heating, heat, energy/heat transfer/exchange,  pressure, temperature.
  • entropy, energy content, energy (enthalpy) and state, motion of particles, speed of particles.
  • (Additional concepts: degree of freedom, vibrational motion, rotational motion, translational motion)

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