Space between two molecules

I have been thinking about what I should write in my first blog for last few hours. Some of the topics I started writing about were too serious for a first write-up and hence I aborted them. I was trying to remember back old days when I used to write random incidents in my diary. Here I start with the following.
Two years back, when I was at TIFR, Mumbai I attended a seminar on Physics education by Prof. Jyotsna Bijapurkar of HBCSE. She was talking about a study conducted by HBCSE on a class of around 35 students who were taught school level Physical sciences. After each session they would often get a quiz set. It was quite amazing to learn about all sorts of different answers from them. In fact the purpose of the study was to learn about the difficulties in understanding certain concepts of Sciences. On one occasion, the students were taught about the concept of constituents of matter like atoms and molecules. The question was: what is in between the gas molecules in a jar of gas (say Carbon di-oxide)? There was an accompanying diagram showing few Carbon di-oxide molecules in the jar.
The answer of the majority: 'Air' !!