OBJECT:
- Part I: To determine the density of two solids, one of which is heavier and the other lighter than an equivalent volume of water.
- Part II: To measure accurately the density of various liquids by means of the Westphal balance.
- Part III: To measure the specific gravity of these liquids by means of a hydrometer.
METHOD: A body is weighed in air and then immersed in a liquid. The apparent loss in weight of the body when immersed in the liquid is, by Archimedes’ principle, equal to the weight of liquid displaced by the body. From these measurements the density and specific gravity of either the solid body or the liquid may be determined.
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OBJECT: To determine the densities of a liquid and a gas by using a balance.
METHOD: Suitable closed vessels of known volume are weighed empty. Each is then filled with either a liquid or a gas and again weighed. By knowing the mass of the liquid or gas, its density is readily calculated.
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OBJECT: To study the manner in which the deflection of a beam depends upon its length, and to determine Young’s modulus by the method of flexure.
METHOD: A uniform rectangular bar supported horizontally on two knife-edges is subjected to a vertical force applied midway between the supports. The deflection of the beam at the midpoint is measured by means of a micrometer screw equipped with an electrical contact. A series of observations is made with a constant load and a varying length of beam (distance between supports). From a logarithmic graph of the deflection versus the length, the mathematical relationship between deflection and length is ascertained. A second series of observations is made in which the load is varied, the length remaining constant. From the slope of a graph of load versus deflection, a value for Young’s modulus is obtained.
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In general, pipets are used to measure and transport very precise volumes of liquids between containers or solutions. The term micropipet is used to describe a pipette that is used to work with very small volumes, less than 1000 ul (1 ml). Research assistants, scientists, and medical laboratory workers are just some of the professionals that utilize pipets in their laboratories.
There are almost countless makes and models of micropipets. Some of the functional features that may differ between models include volume range, incremental units, mode of operation (electronic or mechanical), autoclavability, and various ergonomic design features. To choose a model that is best for your laboratory and the proposed activity it is important to consider these features.
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OBJECT: To make an experimental determination of the mechanical equivalent of heat using a continuous flow calorimeter.
METHOD: A stream of water flowing through a glass tube is heated by an electric current passing through a heating element contained in the tube. The temperature difference between the water entering and leaving the tube depends upon the amount of energy supplied per unit time to the heating element (power input) and upon the mass of water flowing through the tube per unit time. A uniform rate of flow of water is maintained and several determinations of the temperature difference are made for corresponding values of the power input. From the measured rate of flow and the slope of a graph of power input versus temperature difference, the value of the mechanical equivalent of heat is determined.
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OBJECT: To study the properties of a compound pendulum, and to determine the acceleration due to gravity by the use of such a pendulum.
METHOD: An experimental pendulum is suspended successively about several axes at different points along its length and the period about each axis is observed. A graph is plotted of the period versus the distance of the axis of suspension from one end of the pendulum. The nature of the graph shows the physical properties of the compound pendulum. From values of the period and the corresponding length of the equivalent simple pendulum as determined from the graph, the acceleration due to gravity is calculated. From the mass of the pendulum and its radius of gyration as obtained from the curve, the rotational inertia of the pendulum is computed.
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