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Water Displacement Method |
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When trying to measure the volume of an irregularly shaped object, the "water displacement method" is the most commonly used technique and the one you will use most often in this chemistry course. The procedure for the water displacement method is listed below. PROCEDURE: 1) Find a graduated cylinder that will be large enough to fit the object(s) being measured. 2) Fill this graduated cylinder enough so that when placed in the graduated cylinder, the object(s) in question will be fully submerged in the water. Also be careful not to put in so much water that the water level will rise past the graduated cylinder’s markings when the object(s) are placed in the graduated cylinder. You must use your own judgment to determine what amount of water meets these requirements. 3) After filling the graduated cylinder to a satisfactory level, record the volume of the water as (a) in your data. Make sure to read the meniscus when determining volume. 4) After the water’s volume has been recorded, carefully place the object(s) in the graduated cylinder and record this volume as (b) in your data. 5) In order to calculate the volume of the irregularly shaped object(s), subtract the volume of the water alone from the volume of the water and object(s) [(b) – (a)]. HINTS & TIPS: * Note that if the object(s) are not fully submerged in the water, the recorded volume of the object(s) is invalid. * Also, if placing the object(s) in the graduated cylinder causes the water level rises past the graduated cylinder’s markings, an accurate reading cannot be made. * Always mass the object(s) before determining volume with the water displacement method. By massing the object(s) after placing them in water, one allows the chance for water to remain on the object(s) after being removed from the graduated cylinder. This could result in the water being massed and, in turn, lead to a source of error. * Use the smallest possible graduated cylinder that is sufficient for measuring the object(s). Smaller graduated cylinders are oftentimes capable of making more accurate measurements than larger graduated cylinders. * The object(s) being measured should not be dropped into the graduated cylinder. This could result in water splashing onto the sides if the graduated cylinder. This water’s volume would go unrecorded and alter the recorded volume of the object(s) in question resulting in a source of error. Please forward all questions, comments and criticisms to Gregory L. Curran.
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