Lesson 5.8: Can Gases Dissolve in Water?

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Carbon Dioxide (CO₂) Molecule

• Carbon dioxide is made up of one carbon atom covalently bonded to two oxygen atoms.
• Although electrons are shared, they are not shared equally between the carbon and the oxygen atoms.
• The oxygen atom has a stronger pull on electrons than the carbon atom.
• This makes the oxygen ends of the molecule slightly negative and the carbon atom slightly positive.

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Carbon Dioxide (CO₂) Dissolved in Water

• Carbon dioxide molecules dissolve in water because the polar areas of water attract the opposite polar areas of carbon dioxide.

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Solubility Curve for Carbon Dioxide (CO₂)

• As the temperature increases, the number of grams of carbon dioxide that can dissolve in water decreases.

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Mentos and Diet Coke Demo

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• Although the candies seem smooth, they have microscopic rough spots.
• The carbon dioxide molecules in the soda attach to these rough spots or nucleation points on the surface of the candies.
• The carbon dioxide builds up into bubbles and the increased pressure pushes the gas and the soda out of the bottle.