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Density Determinations Lab Title: Density determination of liquids and solids Question: How does type of substance affect its density? Introduction – Purpose: - To determine the density of solids and liquids To practice and learn good lab techniques Introduction – Background Research (paraphrase) For this lab’s background research section in the lab report, you will need to PARAPHRASE the following in your lab report The density of a sample of matter represents the mass contained within a unit volume of space in the sample. For most samples, a unit volume means 1.0mL. The units of density, therefore, are quoted in terms of grams per milliliter (g/mL) for most solid and liquid samples of matter. The density of a sample represents the mass of the specific sample divided by its particular volume. The equation for density is: where D = density, M = mass, and V = volume. Because the density does in fact represent a ratio, the mass of any size sample, divided by the volume of that sample, gives the mass that 1.0 mL of the same sample would possess. In other words, the density of a pure substance will always be the same as the density of another sample of the same substance. The determination of the density of certain physiological liquids is often an important screening tool in medical diagnosis. For example, if the density of urine differs from normal values, this may indicate a problem with the kidneys secreting substances which should not be lost from the body. The determination of density is almost always performed during a urinalysis. Several techniques are used for the determination of density. In general, a density determination will involve the determination of the mass of the sample with a balance, but volume measurement will differ from situation to situation. For irregular solids, it may be possible to determine the volume of the solid from Archimedes’ principle, which states that an insoluble, nonreactive solid will displace a volume of liquid equal to its own volume. An irregularly shaped solid is added to a liquid in a container such as a graduated cylinder and the change in liquid level is determined. For liquids, a routine method for density determination is to weigh a particular volume of liquid as contained in a graduated cylinder. Introduction – Hypothesis (fill in the blanks) Since ______________________________________________________________________________, If water, oil, rubbing alcohol, and 40 volume clear developer’s densities are measured, Then _______________________________________________________________________________. Materials Graduated Cylinder Scale Beaker Distilled water 70% rubbing alcohol 40 volume clear developer Metal BBs Baby oil Methods Density of BBs 1. 2. 3. 4. 5. 6. 7. Take mass of beaker Place BBs in beaker Take mass of beaker and BBs. Pour 25 mL of tap water into graduated cylinder Pour BBs into graduated cylinder with water Measure new volume in graduated cylinder Take difference of volumes to get volume of BBs, calculate density Density of Liquids 1. 2. 3. 4. 5. 6. Take mass of graduated cylinder Pour between 15-25 mL of distilled water into graduated cylinder Take new mass of graduated cylinder, take difference to get mass of liquid Read volume of liquid from graduated cylinder Calculate density Repeat steps 1-5 with rubbing alcohol, 40 volume clear developer, and baby oil (ONLY USE GLASS GRADUATED CYLINDER FOR BABY OIL) Data Tables Table 1. Density of Metal BBs Unit (fill in) Mass of BBs and Beaker grams Mass of Beaker by itself Mass of BBs Volume of Water + BBs Volume of Water by itself Volume of BBs Density of BBs Table 2. Density of Liquids Liquid Unit (fill in) Mass of Liquid + Graduated Cylinder Mass of Mass of Graduated Liquid Cylinder by itself Volume of Liquid Density of Liquid