WJEC Chemistry Practice Exam 2026 - Free Chemistry Practice Questions and Study Guide

The test for identifying oxygen involves placing a glowing splint in the gas. Oxygen supports combustion, which means it is capable of igniting materials and allowing fires to burn more vigorously. When a glowing splint is introduced into a sample of oxygen, the splint will reignite and burst into flames due to the increased oxygen concentration. This characteristic makes the glowing splint test a reliable method for detecting the presence of oxygen.

In contrast, other methods such as placing a burning splint in the gas or lighting the gas with a flame do not specifically indicate the presence of oxygen, as those tests are more aligned with identifying flammable gases or assessing combustion properties. Bubbling gas through limewater is used to identify carbon dioxide, not oxygen, as limewater turns cloudy in the presence of carbon dioxide. This differentiation is key in understanding the specific tests used for various gases.