- Water heated on a stove receives heat from the bottom, where the pan or container in which it's being heated makes contact with the stovetop. Water heated in a microwave gets hit with microwaves from every angle. Stove heating creates convection currents that ensure the water is heated evenly throughout. This doesn't happen with water heated via a microwave, and since the microwave molecules hit the water at random, it's not heated evenly. This is the reason why sometimes liquids heated in a microwave have cold and hot spots.
- Heating water via the convection action created on a stove takes more time than heating via microwave, because the microwave particles very quickly cause the water molecules to vibrate, and the vibrations result in heating.
- When water heated on a stove reaches its boiling point, it stays at that point until you remove it from the heat and allow it to cool. This is not so with water heated in a microwave, which will heat water to a temperature above the boiling point. This is sometimes referred to as "superheating." Yet because a microwave does not heat water evenly, some parts of water in a container may be above boiling while others are below that temperature.
- If you need to heat a cup of water fast, the microwave is your best bet. However, sometimes slow is best. For instance, if you're making a cup of tea, you may want to heat your water on the stove top. This will ensure that your water has the same temperature throughout, which means you won't burn your tongue on a super hot spot and your tea won't cool down too quickly because of cool spots. If heating water in a microwave, avoid superheating by putting a wooden stir stick or other nonmetallic item in your cup before turning on the microwave. This will help avoid your cup of water exploding when you take it out.