| A | B |
|---|
| temperature | measure or degree of hotness or coldness of air or liquids measured by a thermometer |
| Fahrenheit | one of two common temperature scales; water freezes at 32°F; water boils at 212°F |
| Celsius / centigrade | one of two common temperature scales; water freezes at 0°C; water boils at 100°C |
| heating surface | the part of the boiler where water is on one side and heat from gases of combustion are on the other side |
| condensate | steam that has lost its heat and turned back into water |
| feedwater | water that is treated for use in the boiler |
| compression tank | allows water to expand in the system |
| first law of thermodynamics | law of conservation of energy = energy cannot be created or destroyed but can be changed from one form to another |
| second law of thermodynamics | heat always flows from a material of higher temperature to a material of lower temperature |
| solid | a substance without an internal cavity that has a definite size and shape |
| liquid | a substance that flows freely and has a definite volume but no independent shape; liquids are only slightly compressible |
| gas | a substance that has no definite volume or independent shape that tends to expand indefinitely |
