Segments in this Video

Chemical Reaction Energy Overview (01:34)


The first law of thermodynamics says energy can neither be created nor lost. Chemists use enthalpy to describe heat, and are interested in its effect on system pressure and volume. View the enthalpy equation.

Exothermic and Endothermic Reactions (03:58)

Reactions releasing heat cause a negative enthalpy change. View a flame tornado demonstration using isopropyl alcohol and oxygen. Heat absorbing reactions cause a positive enthalpy change; view a demonstration using ammonium chloride and barium hydroxide to produce ammonia.

Measuring Heat (01:34)

Sodium hydroxide added to water in a Styrofoam cup increases temperature by 5 degrees Celsius. The temperature change is converted to calories or joules.

Mississippi Biofuels (02:52)

Agricultural scientists use calorimeters to calculate which crops would serve as alternative fuel sources. They measure the energy potential of crop residues. Sweet potato farmers could enhance productivity by selling imperfect produce.

Testing Potential Biofuel Sources (03:50)

Scientists process crop samples and measure energy content in a bomb calorimeter. Hear the difference between food and chemistry calories. They record water temperature difference before and after calorimeter ignition.

Potential Biofuel Results (02:02)

Using a bomb calorimeter, scientists calculate remaining ash weight of crop samples, water temperature, and heat capacity to determine energy content. Sweet potatoes produce the most calories and could be used for local fuel production.

Bond Enthalpy (02:20)

Chemists can calculate molecular bond enthalpy to predict reaction behavior. For instance, they can create a model of the reaction of MMH combined with nitric acid.

Heat to Work Conversion (01:21)

Work is any change in system energy that is not a heat transfer. 19th century scientists discovered it is impossible to convert 100% heat to mechanical energy—leading to the second law of thermodynamics.

Fighting the 2nd Law of Thermodynamics (01:59)

Automotive researchers work to improve engines efficiency. Hear why spark plug timing is important in the combustion chamber.

Improving Engine Efficiency (04:14)

A PV diagram represents work extracted in a spark plug cycle. In addition to pressure and volume, exhaust temperature indicates wasted heat. Earlier spark timing is more efficient.

Credits: The Energy in Chemical Reactions: Chemistry: Challenges and Solutions (00:26)

Credits: The Energy in Chemical Reactions: Chemistry: Challenges and Solutions

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The Energy in Chemical Reactions: Chemistry: Challenges and Solutions

Part of the Series : Chemistry: Challenges and Solutions
3-Year Streaming Price: $149.95



Many chemical reactions involve explosions, bubbling gases, flames, and smoke because energy is being transferred from one form to another—the realm of thermodynamics. Thermodynamics, the rules for predicting the progress of a reaction and harnessing the energy released, is key to solving engineering problems, such as making cleaner and more efficient automobile engines.

Length: 28 minutes

Item#: BVL110254

Copyright date: ©2014

Closed Captioned

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