HM_Density Lab 2.pdf - Measuring Density Lab(Hayden-McNeil...

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Measuring Density Lab (Hayden-McNeil Lab Simulation) Background Why Does Ice Float on Water? In general, solid substances are denser than liquids. However, ice floats on liquid water. This occurs because ice is less dense than water. The water molecules that make up ice form an ordered crystal using hydrogen bonds. The crystal structure of ice keeps water molecules farther apart than the water molecules in liquid water are. This gives ice a lower density than water. Therefore, ice floats. All matter has mass and volume , which means it takes up space. The relationship between these values defines a fundamental characteristic of matter known as density . A characteristic property can be used to identify elements or compounds. Density is defined as mass per unit volume of a substance and is computed using the equation : d= m/V where d is the density of a substance, m is its mass, and V is its volume. The standard metric unit for density is grams per milliliter (g/mL). For solids, sometimes the cubic centimeter is used instead, and the unit of density is then grams per cubic centimeter (g/cm 3 ). Numerically the two volume units are equivalent, because 1 cm 3 is equal to 1 mL. The density of a substance is a characteristic property that can be used to identify matter by type. For example, the density of copper is 8.96 g/mL. Therefore, if you calculate the density of an unknown metal to be 8.96 g/mL, the metal is most likely copper. Measuring Mass Much of the practice of chemistry involves taking measurements. It is important to take measurements accurately and record information in an organized fashion so that it can be used at some point in the future. The mass of a substance can be measured using a balance . There are many types of balances, but the one most commonly used is the electronic balance. An electronic balance gives fast results on a digital display. An example of an electronic balance is shown in the figure on the right.
Measuring the Volume of a Liquid The volume of a liquid is usually measured using volumetric equipment, such as a graduated cylinder. Due to the adhesion forces between a liquid and the walls of the cylinder, the surface of a liquid will curve and form a meniscus . The meniscus can be either concave (curving upward) or convex (curving downward). To minimize

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