U3 s1 L1 Systems - revisted

Systems and Their Surroundings a system is a substance or a group of substances undergoing a thermal, physical, chemical, or nuclear change. The surroundings is anything that is in thermal contact with the system. Together, system and its surroundings make up a universe.

3 types of systems 1.Closed open to the flow of energy, but closed to the flow of matter For example, a gel filled freezer pack is a closed system. Heat can flow out of the pack when it is put into the freezer, or into the pack when it is placed in a portable cooler. The gel however, stays inside the plastic packaging. System – gel Surroundings – outside environment. –a sealed bottle of soda cooling in a refrigerator –a reaction taking place in an aqueous medium e.g. acid-base neutralization reaction –nitrogen dioxide reacting to produce dinitrogen tetraoxide in a closed reaction vessel

2. Open –A system that is open to the flow of energy and matter An open glass of cold water on the counter. It can absorb energy from the outside air and it can lose mass via evapouration of the water. For example, a “cold pak” contains a inner pouch of NH 4 NO 3(s).inside a larger sealed pouch of water. When the pouch of NH 4 NO 3(s) is broken it dissolves in the water. The process of dissolving absorbs energy from the water and the water cools. –System – dissolving NH 4 NO 3(s). –Surroundings – water in the pouch. –This is an open system in the sense that energy flows from the sys to the surroundings and the system combines and becomes part of the surroundings

3. Isolated –A system that is closed to the flow of energy and matter