Determination of Density of Solids and Liquids

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Determination of Density of Solids and Liquids
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Terms to Learn

• Accuracy
• Precision
• Absolute Error
• Relative Error
• Linear Regression
• Intensive Property
• Extensive Property
• Density

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Accuracy

• Accuracy refers to the degree of agreement
  between a measured value and the true value or
  accepted value.
• You can say in another way Accuracy is telling
  the truth

Accuracy
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Precision

• Precision is the degree of agreement between
  replicate measurement of the same quantity.
• In another way Precision is telling the same
  story over and over again

Precision
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Accuracy and Precision

• All accurate data are Precise but all Precise
  data are not accurate.

Accuracy with Precision
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Errors

• Multiple measurements are necessary to avoid
  errors.
• Standard Deviation represents the precision in a
  measurement.
• The accuracy of a measurement can be expressed by
  another terms are called
• 1. Absolute Error
• 2. Relative Error

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Absolute Error

• Absolute error is the simple difference between
  measured value and the true or accepted value.
• This will have the same unit as the measured
  quantity.
• Absolute Error Measured Value Accepted Value

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Relative Error

• The relative error nothing but the absolute error
  divided by the True or Accepted value
• The percent relative error is the relative error
  times 100.
• Relative error is a dimensionless quantity.
• Measured Value Accepted Value Accepted
  Value

Relative Error
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Linear Regression

• A simple regression model includes two variables.
• One independent variable and One dependent
  variable.
• A (simple) regression model that gives a
  straight-line relationship between two variables
  is called a linear regression model

Linear
Non Linear
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Linear Regression

• How to draw a best fit line in Excel.
• I am going to draw a graph of Temperature Vs Ice
  Cream Sale.
• Independent Variable goes to X-axis.
• Dependent Variable goes to Y-axis.

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Properties of Matter

• There are two important properties for matters
• 1. Intensive Property
• 2. Extensive Property

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Intensive Property

• Intensive property independent of the amount of
  the substance.
• Also called Intrinsic Property
• Example Melting Point, Boiling Point, Density

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Extensive Property

• Extensive Property depends on the amount of the
  substance.
• Also called Extrinsic Property
• Example Mass, Concentration, Volume

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Density

• Today we are going to find the density of an
  unknown solid and unknown liquid.
• Density Mass / Volume.
• The unit is g / mL (SI Kg / m3).

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Density

• Archimedes, the Greek Mathematician discovered
  the principle of Density and Buoyancy (Also known
  as Archimedes Principle), when he was taking a
  bath!!!

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Density of Solids

• Get your unknown sample from the centre desk.
• Find the mass of each metal piece.
• Partially fill a graduated measuring cylinder and
  note down the reading.
• Add your metal piece into the cylinder and again
  note down the reading.

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Density of Solids

• The sample must be completely submerged into
  the liquid.
• The difference in two volume readings is the
  volume of your sample

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Density of Liquids

• Take a 50 mL of Erlenmeyer Flask and find its
  mass.
• Get your unknown liquid from the centre desk.
• Take a pre-washed burette.
• Rinse your burette with small portion of the
  unknown liquid.
• Then fill the burette with your unknown.
• Do not forget to fill the burette tip!
• Note down the initial reading.

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Density of Liquids

• Dispense 5 mL of the liquid from the burette
  into the pre-weighed Erlenmeyer Flask.
• Note down the burette reading again.
• Find the mass of the flask (with the liquid)
  again.
• Dispense 5 mL of the liquid again, note down
  the burette reading and weigh the flask again.

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Density of Liquids

• Do this step 3 more times.
• Make a plot Mass Vs Volume using Excel.
• Find the density of the liquid from the graph.
• Find the standard deviation of the slope.