Bananas turned into hammers, rubber balls shattered like glass, flowers turned to dust.
A chemical engineer ran these liquid-nitrogen experiments at an expo at William Clarke College, Kellyville, to show students in years 9 to 11 the many career paths available in engineering.
Students from nine other schools, including Carlingford High School , attended the event run by Engineers Australia on Tuesday.
Careers adviser at William Clarke College, Maureen Tweed, said students were "gobsmacked" by some of the experiments.
"One of the biggest problems with maths and science is a lot of kids don't see its relevance," she said.
"When they come to something like this where they've got to do the mechanics and calculate angles for car racing, all of a sudden it becomes real."
Engineers Australia Sydney division president Alexandra Meldrum said they wanted to encourage students to participate in science and maths at school and ensure they're aware of the possible careers in the industry.
Engineering course providers including TAFE Western Sydney Institute, the University of Western Sydney, the University of NSW and the Australian Defence Force Academy, were also there to answer students' questions.
Daryl Chiu, of year 11, hopes to become a biomedical or chemical engineer. He studies physics, chemistry and biology and said the day was helpful.
‘‘I’ve learnt a lot about what engineering actually is and all the different career opportunities that engineering can give you,’’ he said.