ON RESISTING FLOW
Investigating a factor affecting the viscosity of a mixture of liquid
The effect of hydrogen bonding on resisting flow of five different liquids
Viscosity is the resistance of a fluid to flow, either within itself, or to moving past an objects moving through it. A liquid with high viscosity is thick and flows slowly. A liquid with a low viscosity is thin and flows quickly. Different liquids have different viscosities.
Factors, which affect viscosity of a liquid, are:
Size of a molecule: Spherical molecules provide less resistance therefore less viscosity compared to oval shaped or disc-like molecule which provide a greater resistance in the flow of liquid. The more spherical molecule is, the lower the viscosity of a liquid.
Temperature: When a solid or liquid is heated, most of the bonds are being broken between particles. In viscosity, the bonds are closer together and they resists the flow, so when the liquid is heated, the bonds are being broken. The liquids with broken bonds flow faster than before.
Intermolecular force: There are three types of intermolecular force between molecules: Hydrogen bonding, van der Waal’s forces and permanent dipole force. Hydrogen bonding is the strongest bond and also has the highest attraction in terms of intermolecular forces. The attraction between molecules is high; the viscosity of a liquid is high.
In this investigation, the purpose is to compare the viscosities of five different liquids and to interpret the results in terms of hydrogen bonding.
In this experiment there should be only one variable, which is varied. In this investigation, the varied variable is five different liquids. To make the experiment as accurate and reliable as possible the following will be done:
The volume of liquid used will be kept constant. The liquid will be measured accurately using a marked line on the side of the beaker.
The stopwatch will be used to measure how long it takes for the marble to sink.
The whole experiment will be repeated and the results will be recorded into a table, from the recordings of the time taken an average will be calculated.
The liquids, which have more hydrogen bonding will have higher viscosity and flow slowly.
Test a liquid’s viscosity by timing how long it takes for the marble to sink. Variables
- The different liquids, which refer to the different number of hydrogen bonding. 2.Dependent variable
- The time that marbles takes to sink in each of the liquids. 3.Controlled variables
|Variable controlled |Why it needs to be controlled |How it will be controlled | |Room temperature |The lower the temperature, the higher the viscosity. |Use an AC or thermometer, set the same | | |Therefore, room temperature can affect the viscosity |temperature in every time you drop the marble. | | |and the time marble sinks. | | |Volume of liquid |The more volume the liquid contained, the faster the |Use a ruler, every liquid in a beaker should be | | |marble sinks. |in the same height. | | | |Use a marked line on the side of the beaker to | | | |measure the same volume. |
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