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The Effects of Anti-freeze on Water (Physical Properties)

Purpose/Objective

The aim of performing this experiment was to:

  1. Evaluate the heating curve of water
  2. Determine the freezing and boiling points of water.
  • Determine the influence of an anti-freeze agent on water’s melting point
  1. Prepare a temperature rate curve of water under the influence of the anti-freeze.
  2. Calculate the molar mass of antifreeze

Introduction

All kinds of matter have boiling and freezing points, temperatures at which they transform from one physical state to another. It is usually affected by certain things as pressure of the surrounding medium and impurities. The ‘normal’ melting and boiling points are the temperatures at which this transformation takes place under atmospheric pressure, for open systems. Closed systems cannot be used to determine the normal temperature because of the controlled conditions of temperature, volume, and pressure, which ate dependent on each other, but independent in the case of open systems.

The boiling and melting points of substances are highly specific, and can, thus, be used to distinguish and separate particular elements and substances from mixtures. For instance, ethanol and water are highly miscible. There exists only one way to physically separate them, which is through a fractional distillation setup. This is possible because alcohol boils at 78.37o C (173.1o F) (Owens and Dikty 25).

An anti-freeze agent (ethylene glycol) is an impurity. Melting and boiling processes take place because individual atoms within these substances acquire enough energy to overcome the intermolecular forces holding them within their static positions. The strength of these forces depend on the types of bonds formed in the chemical structures. Examples include ionic bonds and covalent bonds. They influence the vapor pressure, which is the pressure of gaseous form of a substance after achieving an equilibrium with its liquid counterpart (“Vapor Pressure”). It is usually inversely proportional to the strength of intermolecular forces, and increases with temperature rise until it is equal to the atmospheric pressure. Impurities have the effect of lowering the melting point and increasing the boiling point because less solvent molecules are found on the surface in comparison to those of an impurity. As a result, anti-freeze substances are used to prevent the boiling of water in car radiators. The properties that are affected by the addition of a nonvolatile solute into a solvent are referred to as colligative properties, and include melting and boiling point, and osmotic and vapor pressure.

Formulas

The molarity of a solution manifests in its boiling and melting points.

Changes in the melting, ΔTf, and boiling points, ΔTb are expressed as

ΔTf =Kf

ΔTb =Kb

Where Kf and Kb are constants of proportionality

Pre-lab questions

  1. What is the effect of anti-freeze on water?
  2. What are the new boiling and freezing points?
  • What is the molar mass of antifreeze

Procedure

  1. Water’s heating curve and anti-freeze
  2. The MicroLab program was opened and a new experiment launched.
  3. Temperature sensors were added and calibrated as per directions, and the calibrations file saved for the experiment. It was dragged to the y-axis.
  4. A Timer sensor was added, and dragged to the x-axis.
  5. Heating was initiated and continued up to the boiling points, shown by the constant reading of temperature.
  6. The data was saved in the file ‘___________’.

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