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Change in Volume, H-Bonding (Ethanol and Water)

  • Page ID
    128793
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    Required Training

    Required PPE

    UC Lab Safety Fundamentals

    Lab coat, safety glasses/goggles,

    nitrile gloves

    Equipment

    Chemicals

    Two 250 mL Volumetric flask with

    DI water and YELLOW food coloring

    500 mL Volumetric flask

    Absolute ethanol and BLUE food coloring

    Digital Thermometer

    Funnel (optional)

    Procedure:

    1) Pour the water solution into the larger flask followed by slowly adding the ethanol without allowing the two to mix and without using a funnel:

    a. The volume is about 500 mL.

    b. Two color layers are visible.

    2) Mix well and note:

    a. The volume decreases due to the “tightening” of the hydrogen bond structure.

    b. The solution changes color.

    Discussion:

    The volume deficit should be about 17.5 mL. If 95% ethanol is used, the shrinkage is still about 15 mL. The structure of liquid water is open because of hydrogen bonding (that is to say, a network holds water molecules with specific orientations towards each other). Crudely we can say that the open (relatively low-density) structure of liquid water is broken much like when ice freezes. The more dense form is reflected in a more compact volume.

    Hazards: clipboard_ec15a24d3ef31b7c1a02ed809da87616e.png

    Ethanol is flammable. Avoid spills, but if one occurs, isolate ethanol from any sources of ignition. Wash affected areas with copious amounts of water.

    Disposal (by Storeroom):

    The mixture will be disposed as hazardous waste.


    Change in Volume, H-Bonding (Ethanol and Water) is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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