The reason a glass dish does not get as hot in the microwave compared to Pyrex or certain plastic containers is due to differences in the materials' properties and how they interact with microwave radiation.
Microwaves heat food by emitting electromagnetic waves that excite water molecules within the food. These excited water molecules produce heat, which then heats the surrounding food. However, microwave ovens work differently when it comes to heating containers.
Glass, being a non-polar material, does not easily absorb microwave energy. Instead, it allows the microwaves to pass through it largely unchanged. As a result, the glass dish does not directly absorb much microwave energy and remains relatively cool.
Pyrex and some plastic containers, on the other hand, are designed to be microwave-safe and are specifically formulated to absorb microwave energy. Pyrex is a type of borosilicate glass that contains materials like boron oxide, which allows it to absorb microwave energy more effectively than regular glass. As a result, it gets hotter as it absorbs more energy from the microwaves.
Certain plastic containers are microwave-safe because they are made from microwave-absorbing materials, such as polypropylene or polyethylene. These materials contain molecules that can absorb microwave energy and convert it into heat. Consequently, the plastic containers can get hot as they absorb and retain more of the microwave energy.
It's important to note that not all plastic containers are microwave-safe, and some can melt or release harmful substances when exposed to high heat. Always check the labeling and instructions on your plastic containers to ensure they are safe for microwave use.
In summary, the differences in heating between glass, Pyrex, and plastic containers in the microwave are primarily due to variations in their material composition and their ability to absorb microwave energy.