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:
- Why did the squash ball and the rose shatter like glass?
- 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)
