William Cullen

Hello! My name is William Cullen, and I want to tell you about my life as a scientist. I was born a long time ago in Scotland, on April 15th, 1710. Even when I was a little boy, I was always asking questions. I wanted to know how everything in the world worked! My curiosity was like a little seed that grew and grew. This love for learning about the world around me made me decide to study medicine when I was old enough. I went to a big school called the University of Glasgow to learn all about science and how to help people.

After I finished my studies, I became a doctor. I enjoyed using my knowledge to help people who were sick feel better. But I soon discovered another great love: teaching! I found so much joy in sharing what I knew with others. In 1747, I started working as a teacher at the same school where I had studied, the University of Glasgow. I taught a subject called chemistry. Chemistry is the amazing science of what things are made of and how they can change, like how water can turn into steam or ice. I loved seeing my students' eyes light up when they understood a new idea. It was wonderful to be both a doctor and a teacher.

One day, I did an experiment that became very famous. I wanted to see what would happen if I made a liquid turn into a gas very, very quickly. Think about how a puddle dries up on a hot day—it turns into a gas called vapor. I found a special way to make this happen almost instantly inside a container. In 1756, I showed my students and other scientists something amazing. As the liquid disappeared into a gas, it pulled all the heat out of the air around it. It got so cold that a small amount of ice formed! It seemed like magic to make ice on a warm day, but it was pure science. This discovery was the very first step that showed people how to create cold, which would one day lead to the invention of refrigerators.

I spent the rest of my life teaching my students and discovering new things about the world. I lived to be 79 years old. My little experiment with making ice was very important. It showed other scientists that it was possible to make things cold on purpose, without needing snow or a chilly day. This idea helped future inventors create the refrigerators and freezers we use all the time. So, the next time you open the fridge for a cold drink or enjoy a yummy ice pop, you can remember my scientific discovery that helped make it all possible.