Warren Irwin's enthusiasm for teaching science knows no bounds.
After 51 years teaching he still delights in seeing a student grasp a difficult concept, and loves sharing his passion for the subject.
On Monday he was awarded an Order of Australia Medal for service to science education.
In 1995 the Winmalee resident created a science textbook called Elementary Atoms, which is used in the science curriculum in 300 schools in Australia, and also in select schools in England, the US and Canada.
"I was trying to find a way to explain stuff that's critical to understand but hard to understand if not explained well," the 72-year-old said.
Using images as well as text, Elementary Atoms explains how atoms join together.
"Bottom year 9 students were jumping up and down in their seats saying 'I can do this'," Mr Irwin said.
The textbook received the CSIRO-BHP Science Award, in the science curriculum category in 1995.
Mr Irwin has taught senior science - physics, biology and chemistry - as well as junior science classes at Sydney schools and Wycliffe Christian School at Warrimoo since the 1960s. He's been teaching science at Nepean Christian School in Mulgoa since 2003.
"Biology is my favourite because I also like taking photos of birds," Mr Irwin said.
He also has a fascination with snakes and is the resident "snake remover" at Nepean Christian School and among friends and neighbours. Some of the captive snakes also end up as teaching tools in the classroom before they're released back into their natural environment.
In years past he's made his own version of science equipment. Many years ago he made it to children's television program The Big Arvo on Channel Seven for his take on Rubens' Tube. The 2m long tube was filled with gas and about 100 flames which changed height depending on the sound frequency pumped into the tube.
The physics apparatus invented by German physicist Heinrich Rubens in 1905, is used to demonstrate the relationship between sound waves and sound pressure.
Initially trained as an industrial chemist, in his early 20s Mr Irwin wanted more out of his job, so he tried his hand at teaching science and gained the necessary teaching qualifications and has never looked back.
"Science has been my passion for a long time," he said.
"I'm also a Christian. Science, it shows me how clever God is and what he's done.
"Whatever way you look at it [the evolutionary process] it's still spectacular."