The hottest part of a candle flame is the outermost zone in which complete combustion takes place.

The hottest part of a candle flame is the zone called the "blue zone."

Explanation:

When a candle burns, it undergoes a process called combustion, which involves the chemical reaction between the wax (fuel) and the oxygen in the air. During this process, the heat generated causes the wax to vaporize and release volatile gases. These gases then mix with the surrounding oxygen and ignite, creating a flame.

A candle flame consists of several distinct zones, each with different temperatures and characteristics. These zones are:

1. Blue Zone: This is the innermost part of the flame and is the hottest region. It appears blue in color due to the complete combustion of the hydrocarbon molecules in the wax vapor. The temperature in this zone can reach up to 1400-1800 degrees Celsius (2552-3272 degrees Fahrenheit).

2. Yellow Zone: Surrounding the blue zone is the yellow zone, also known as the luminous zone. This region is slightly cooler than the blue zone and has a temperature range of around 800-1400 degrees Celsius (1472-2552 degrees Fahrenheit). The yellow color is a result of incandescent soot particles that are not completely burned.

3. Outer Zone: The outermost part of the flame is the outer zone, also called the non-luminous zone. This zone has the lowest temperature, ranging from approximately 300-800 degrees Celsius (572-1472 degrees Fahrenheit). It is primarily composed of unburned hydrocarbon molecules that are still undergoing combustion.

Summary:

The hottest part of a candle flame is the blue zone, which is the innermost region of the flame. It is characterized by intense heat and appears blue due to complete combustion. The temperature in this zone can reach up to 1400-1800 degrees Celsius.