---
title: "System — AP Chemistry Definition & Exam Guide"
description: "In AP Chem, a system is the specific part of the universe you're studying, like a reaction in a calorimeter. It's the foundation of every heat transfer problem in Unit 6."
canonical: "https://fiveable.me/ap-chem/key-terms/system"
type: "key-term"
subject: "AP Chemistry"
---

# System — AP Chemistry Definition & Exam Guide

## Definition

In chemistry, a system refers to a specific portion of matter that is being studied or observed. It can be as small as an individual molecule or as large as an entire container of gas.

## Review

### Related Terms

- [Closed System](/ap-chem/key-terms/closed-system): A type of system that allows for the exchange of energy with its surroundings but not matter.
- [Open System](/ap-chem/key-terms/open-system): A type of system that allows for both the exchange of energy and matter with its surroundings.
- [Isolated System](/ap-chem/key-terms/isolated-system): A type of system that does not allow for any exchange of energy or matter with its surroundings.