A room that is 40 feet by 65 feet with a 10-foot-high joisted ceiling will be protected with heat detection. The joists are 12 inches deep and run in the 40-foot direction. The engineer specified heat detectors with a 50-foot listed spacing. How many heat detectors are required for this room?

In a laboratory experiment, a fermenting aqueous solution of glucose and yeast produces carbon dioxide gas and ethanol. the solution was heated by burning natural gas in a bunsen burner to distill the ethanol that formed in the flask. during the distillation, the ethanol evaporated and then condensed in the receiving flask. the flame of the burner was kept too close to the bottom of the flask and some of the glucose decomposed into a black carbon deposit on the inside of the flask. during this experiment the following changes occurred. which of these changes involved a physical change and not a chemical change? check all that apply. 1-condensation of ethanol 2-evaporation of ethanol 3- formation of carbon dioxide gas from glucose burning of natural gas 4-formation of ethanol from glucose by yeast 5-formation of a carbon deposit inside the flask

Can someone me with questions 12 and 13 plz.

What best discribes the relationship between wavelength and frequency in a electromagnetic wave