A heat engine is used to lift a 4500-kg load to a height of 3 m at a constant speed. During the lifting process, the engine received 400,000 J of heat from the fuel burned in its interior. What is the efficiency of the engine?

Sphere 1 has an emissivity of 0.85, its radius is 1 m, and its temperature is 35 °C. Sphere 2 has an emissivity of 0.45 and a radius of 1 m. What should be the temperature of Sphere 2 so it emits radiation at the same power as Sphere 1? 

A student does 1290 J of work while studying.  In the process, her internal energy decreases by 2490 J.  Determine the value of Q, including the algebraic sign.

A student does 1500 J of work while studying.  In the process, her internal energy decreases by 2600 J.  Determine the value of Q, including the algebraic sign.

A circular hole in a copper plate is 2.435 cm in diameter at 20.0 °C.  What is the diameter of the hole if the temperature of the plate is raised to 160.0 °C?  The coefficient of linear expansion of copper is 17 × 10–6/C°. 

A heat engine operates between a hot reservoir at 2500 K and a cold reservoir at 500 K.  During each cycle, 2.5 × 105 J of heat is removed from the hot reservoir and 5 × 104 J of work is performed. Determine the maximum possible efficiency of this engine.

When is hydrolysis used?

Which indicator changed from blue to orange/red as a positive result?

Which substance was used as the control when testing for the presence of organic molecules?

Match the organic molecule with its description. Letters can be used more than once.