When sodium is heated in air, it starts burning with ________ and forms a mixture of sodium oxide and sodium peroxide.

When sodium is heated in air, it starts burning with orange flame and forms a mixture of sodium oxide and sodium peroxide.

When smaller pieces of sodium is taken, it burns with pale orange or yellowish-orange, however, when bigger pieces of sodium is taken, a bright orange flame is produced. 

Regardless of the amount of sodium, it reacts with oxygen in air to form white sodium oxide.