Experiment 4 Fisika

EXPERIMENT 4 AIM To determine the density of a stone (a non-porous solid of irregular shape) BASIC THEORY The density of a material is defined as its mass per unit volume:

Different materials usually have different densities, so density is an important concept regarding buoyancy, metal purity and packaging. In some cases density is expressed as the dimensionless quantities specific gravity or relative density, in which case it is expressed in multiples of the density of some other standard material, usually water or air. For a homogeneous object, the mass divided by the volume gives the density. The mass is normally measured with an appropriate scale or balance; the volume may be measured directly (from the geometry of the object) or by the displacement of a fluid. If the body is inhomogeneous, the density is a function of the coordinates , where dv is elementary volume with coordinates . The mass of the body then can be expressed as

, where the integration is over the volume of the body V. A very common instrument for the direct measurement of the density of a liquid is the hydrometer, which measures the volume displaced by an object of known mass. A common laboratory device for measuring fluid density is a pycnometer; a related device for measuring the absolute density of a solid is a gas pycnometer. Another instrument used to determine the density of a liquid or a gas is the digital density meter - based on the oscillating U-tube principle.

The density of a solid material can be ambiguous, depending on exactly how its volume is defined, and this may cause confusion in measurement. A common example is sand: if gently filled into a container, the density will be low; when the same sand is compacted into the same container, it will occupy less volume and consequently exhibit a greater density. This is because sand, like all powders and granular solids contains a lot of air space in between individual grains; this overall density is called the bulk density, which differs significantly from the density of an individual grain of sand. APPARATUS • A piece of stone • Measuring cylinder • Water • Thread • Balance PROCEDURE 1. Weight the stone to determine its mass (m) 2. Pour water into the measuring cylinder to about one-third of its depth. Record the volume of water in the measuring cylinder, V1 in cm3. 3. Attach the piece of stone to a piece of thread about 50 cm long and lower the stone gently into the water. Record the volume of the water plus the stone in the measuring cylinder, V2 in cm3. 4. Empty the cylinder, dry the stone and repeat the experiment twice using slightly different value of V1. RESULTS Mass, (m) = 50,69 g 1st attempt 2nd attempt 3rd attempt

V1 in cm3 V2 in cm3 50 cm3 59 cm3 3 60 cm 68 cm3 80 cm3 87 cm3 Average volume of stone

Density of stone =

mass Volume

=

50,699 g 8 cm3

Volume of stone = (V1 - V2) in cm3 9 cm3 8 cm3 7 cm3 8 cm3 =

6,33 g/cm3

CONCLUSION The density of stone = 6,33 g/cm3

QUESTIONS 1. Explain why it is not possible to use the experiment to determine the density of cork. → Because the cork absorb the water and float in the water, so that is can’t be determine the density. 2. How should the experiment be modified such that density of cork be determined? →

Asessor:

The experimenters : IL Rahma Pradira Gesari Inayah Nur Utami Khairina Izzati Amalia Konita Septiasti

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