? energy

Our task is to determine how much energy is required to accomplish this.From the discussion in the text, we know that 4.184 J of energy is re-

quired to raise the temperature of one gram of water by one Celsius degree.

4.184 J

Because in our case we have 7.40 g of water instead of 1.00 g, it will take7.40 � 4.184 J to raise the temperature by one degree.

7.40 � 4.184 J

However, we want to raise the temperature of our sample of water by morethan 1 �C. In fact, the temperature change required is from 29.0 �C to 46.0 �C. This is a change of 17.0 �C (46.0 �C � 29.0 �C � 17.0 �C). Thus we will

7.40 g waterT � 30.0 �C

7.40 g waterT � 29 �C

1.00 g waterT � 30.0 �C

1.00 g waterT � 29.0 �C

7.40 g waterT � 46.0 �C

7.40 g waterT � 29.0 �C

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C H E M I S T R Y I N F O C U S

Nature Has Hot Plants

The exotic-looking voodoo lilyis a beautiful and seductiveplant. The voodoo lily featuresan elaborate reproductivemechanism—a purple spikethat can reach nearly 3 feet inlength and is cloaked by ahoodlike leaf. But approach tothe plant reveals bad news—itsmells terrible!

Despite its antisocial odor,this putrid plant has fascinat-ed biologists for many yearsbecause of its ability to gener-ate heat. At the peak of itsmetabolic activity, the plant’sblossom can be as much as 15�C above its surrounding tem-perature. To generate thismuch heat, the metabolic rateof the plant must be close tothat of a flying hummingbird!

What’s the purpose of thisintense heat production? For aplant faced with limited foodsupplies in the very competi-tive tropical climate where it

grows, heat production seemslike a great waste of energy.The answer to this mystery isthat the voodoo lily is polli-nated mainly by carrion-lovinginsects. Thus the lily preparesa malodorous mixture ofchemicals characteristic ofrotting meat, which it then“cooks” off into the surround-ing air to attract flesh-feedingbeetles and flies. Then, oncethe insects enter the pollina-tion chamber, the high tem-peratures there (as high as110 �F) cause the insects toremain very active to bettercarry out their pollinationduties.

The voodoo lily is only oneof many thermogenic (heat-producing) plants. Theseplants are of special interest tobiologists because they pro-vide opportunities to studymetabolic reactions that arequite subtle in “normal” plants.

A voodoo lily.

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