Here's how you can quickly open Chrome apps in their own window, outside of your browser.
1. Hold the Shift key.
2. Click on the app shortcut in the Chrome App Launcher.
3. Your app will launch in its own window.
Chrome OS is built around a browser, but not every Chrome app has to run inside a browser tab. Sometimes it makes more sense to break out an app from the confines of Chrome; particularly if you have a large-screen Chromebook or use Chrome OS on an external monitor.More at Gigaom
Additional resources for Chrome OS