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Discover how sensitive a shark’s sense of smell is.
What You Need:
- Six large jars or beakers.
- Red food coloring.
- Some cologne, perfume or other smelly liquid.
To Do and Observe:
Pour 500 ml (17 oz) of clean water into each beaker / jar. In one beaker place 10 drops of red food coloring. Stir gently to mix. In the second beaker place 5 drops of food coloring. Stir gently to mix. In the third beaker place only one small drop of food coloring. Stir gently to mix. Examine each jar. The remaining three beakers should be well separated in the room. In one beaker place 10 drops of cologne. Stir gently to mix. In the second beaker place 5 drops of cologne. Stir gently to mix. In the third beaker place only one small drop of cologne. Stir gently to mix. Sniff each beaker and note any differences.
What's Going On:
The shark’s ability to detect prey by its sense of smell is exceeded only by its ability to detect sounds or vibrations in the water. Some sharks can smell potential prey from a distance of up to 90 meters (about the length of a football field). A shark’s minimum sensitivity to smell blood is about one part per million (ppm). The beaker with 10 drops of coloring / cologne represents a concentration of about 1000 ppm (parts per million). The beaker with 5 drops represents about 500 ppm. The beaker with one drop represents about 50 - 100ppm. This concentration is still 50 times the minimum amount a shark can detect.
Try changing the concentrations of your mixtures and see how sensitive your noses are. Parts per million (ppm) can be calculated using the ratio: one drop in 1000ml of water = 50 ppm.