Science Buddies: "Ask an Expert"

My project question is What is the freezing time for ice cream using ice, rock salt and ice, and table salt and ice?

This sounds like an interesting science project to work on. Do you have specific questions about your project that you are looking for help with? If you run into questions as you work on your experiment, please post back in this thread, and our Experts can offer input.

Amy
Science Buddies

What is happening when things freeze?
what is freezing?
why do things freeze?
what does chemistry have to do with ice cream?

Hello,
Freezing is a phase change, and phase changes are very familiar to all of us. A phase change is when one state of matter - usually solid, liquid, or gas - changes to another state. The temperature of a substance describes the energy and movement of its particles. The particles of a liquid have some freedom of movement and can slide past each other to take the shape of their container. When a liquid's temperature is lowered to its freezing point, some energy leaves the substance (which is called an exothermic process) so that the particles move around less. They usually settle into a crystal structure, and there you have a solid. What makes ice cream special is that it does not have large ice crystals. Ice cream is churned as it freezes to keep the crystals small and work in air, which makes the ice cream smooth.

Chemistry has a whole lot to do with ice cream, and with everything we encounter. Someone like a food science technician uses chemistry to improve ice cream's texture, flavor, and shelf life with additives.