Lab Manual: Density of Solid | Lab Manuals for Class 9 PDF Download

Objective

Theory

• Density: The density of a substance is defined as the mass per unit volume,[D = M/V]
  Here, D = Density of the body
  M = Mass of the body
  V = Volume of the body.
• S.I. unit of density = Kgm^-3 or Kg/m^-3
  c.g.s. unit of density = g/cm^-3 or g cm^-3
• Floating bodies: The density of water is 1 g/cm³ (c.g.s. system) and 1000 kg/m³ (S.I. system).
• Case (a) If the density of a body is more than 1 g/cm³ or 1000 kg/m³ then the body will sink in water.
• Case (b) If the density of a body is less than 1 g/cm³ or 1000 kg/m³ then the body will float on water.
• Case (c) If the density of a body is same i.e. 1 g/cm³ or 1000 kg/m³ then the body will half float and half submerge in water.
  

• The force due to the gravitational attraction of the earth that acts on a body is called weight.
• (Weight) Force = mass x acceleration.
  Force = mass x acceleration due to gravity (g)
  Force = mass x g
  i.e     Weight = m x g
• Weight of a body = Force on the body.
• S.I. unit = Newton = 1 kg m/s²
• N =1 kgf= 1 kilogram force,
  i.e    g = 9.8 m/s²
• Weight is measured by spring balance.

Materials Required

Procedure

• Tie a metal bob (or any solid) with the string of cotton to the hook of the spring balance. The spring balance should be checked for any error. Let the zero error be ‘x’.
• Hold the spring balance (or tie it to the stand), suspended with the metal bob in air. Measure the weight of the bob. Let its weight be ‘W_F‘
• Pour the water in the measuring cylinder and record the initial volume of water, let it be   ‘ V₁‘
• Suspend the metal bob into the measuring cylinder with water. The bob should not touch the base, nor the sides of the cylinder.
  The water level rises, measure the increased water level, let this volume be ‘ V_F‘
• Record all your observations in the observation table and do the calculation to find the density of a given solid metal bob.
  

Observations

1. Weight of the given Metal Bob = 400N
2. Mass of the Metal Bob = 400/9.8 = 40.8g

1. Volume of water displaced by solid (metal bob) = 20 mL.
2. Density of a solid (metal bob) =40.8g/20ml = 2.04 g/cm³
   1 mL of water = 1 cm³

Result

Precautions

• The spring balance should be sensitive.
• The zero error in the spring balance should be recorded before it is used to find the weight of solid.
• Record the readings carefully of both spring balance and measuring cylinder by keeping the level of eye and the mark of reading same/parallel.
• The solid/metal bob should not touch the bottom, or sides of the measuring cylinder.
• If the zero error in spring balance is 1 N then subtract this error from the final reading of the weight of solid/ metal bob.