Q. Why does water simmer before it boils?
A. The particles of water near the bottom of the kettle (being formed into steam sooner than the rest) shoot upwards; but are condensed again (as they rise) by the colder water, and produce what is called “simmering.”
Q. What is meant by simmering?
A. A gentle tremor or undulation on the surface of the water. When water simmers, the bubbles collapse beneath the surface, and the steam is condensed to water again: but when water boils, the bubbles rise to the surface, and steam is thrown off.
Q. Why does a kettle sing when the water simmers?
A. Because the air (entangled in the water) escapes by fits and starts through the spout of the kettle; which makes a noise like a wind instrument, when it is blown into.
Q. Why does not a kettle sing, when the water boils?
A. As all the water is boiling hot, the steam meets with no impediment, but freely escapes in a continuous stream.
Q. When does a kettle sing most?
A. When it is set on a hob to boil.