BIOLOGY PRACTICAL ACTIVITIES
To Show the Gas Produced When the Food is burned
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A little food substance e.g., maize flour or meat is placed inside a boiling tube. The boiling tube is stoppered using a rubber bung connected to a delivery tube inserted into a test-tube with limewater. The food is heated strongly to bum. Observations are made on the changes in lime water (calcium hydroxide) as gas is produced.
The clear lime water turns white due to formation of calcium carbonate precipitate proving that carbon (Iv) oxide is produced.
Experiment to Show the Gas Produced During Fermentation
Glucose solution is boiled and cooled. Boiling expels all air. A mixture of glucose and yeast is placed in a boiling tube, and covered with a layer of oil to prevent entry of air. A delivery tube is connected and directed into a test-tube containing lime water. The observations are made immediately and after three days the contents are tested for the presence of ethanol.
A control experiment is set in the same way except that yeast which has been boiled and cooled is used. Boiling kills yeast cells. The limewater becomes cloudy within 20 minutes. This proves that carbon (IV) oxide gas is produced. The fermentation process is confirmed after three days when alcohol smell is detected in the mixture.
Experiment to Show Germinating Seeds Produce Heat
Soaked bean seeds are placed in a vacuum flask on wet cotton wool. A thermometer is inserted and held in place with cotton wool . The initial temperature is taken and recorded. A control experiment is set in the same way using boiled and cooled bean seeds which have been washed in formalin to kill microorganisms.
Observation is made within three days. Observations show that temperature in the flask with germinating seeds has risen. The one in the control has not risen. Comparison Between Aerobic and Anaerobic Respiration