Performing Experiments
Contents
A learner wondered whether the rate of evaporation of a substance was related to the boiling point of the substance. Having done background research they realised that the boiling point of a substance is linked to the intermolecular forces within the substance. They know that greater intermolecular forces require more energy to overcome. This led them to form the following hypothesis:
The larger the intermolecular forces of a substance the higher the boiling point. Therefore, if a substance has higher boiling point it will have a slower rate of evaporation.
Perform the following experiment that the learner designed to test that hypothesis.
The boiling points and rate of evaporation experiment is a very simple one meant to introduce the learners to the concept of the scientific method in a practical way. It has been broken up into three parts: performing the practical investigation, analysis of results, drawing conclusions.
The learners should be as accurate as possible when measuring the drop in volume as they will be required to plot a graph of their data.
Experiment: Boiling Points and Rate of Evaporation Part 1
Aim
To determine whether the rate of evaporation of a substance is related to its boiling point.
Apparatus
You will need the following items for this experiment:
- \(\text{220}\) \(\text{ml}\) water, \(\text{20}\) \(\text{ml}\) methylated spirits, \(\text{20}\) \(\text{ml}\) nail polish remover, \(\text{20}\) \(\text{ml}\) water, \(\text{20}\) \(\text{ml}\) ethanol
- One \(\text{250}\) \(\text{ml}\) beaker, four \(\text{20}\) \(\text{ml}\) beakers, a thermometer, a stopwatch or clock
Method
Warning:
All alcohols are toxic, methanol is particularly toxic and can cause blindness, coma or death. Handle all chemicals with care.
- Place \(\text{200}\) \(\text{ml}\) of water into the \(\text{250}\) \(\text{ml}\) beaker and move the beaker to sunny spot. Place the thermometer in the water.
- Label the four \(\text{20}\) \(\text{ml}\) beakers \(\text{1}\) – \(\text{4}\). These beakers should be marked.
- Place \(\text{20}\) \(\text{ml}\) methylated spirits into beaker 1, \(\text{20}\) \(\text{ml}\) nail polish remover into beaker 2, \(\text{20}\) \(\text{ml}\) water into beaker 3 and \(\text{20}\) \(\text{ml}\) ethanol into beaker 4.
- Carefully move each beaker to the warm (sunny) spot.
- Observe each dish every two minutes. Note the volume in the beaker each time.
- Continue making observations for \(\text{20}\) \(\text{minutes}\). Record the volumes in a table.
Results
Record your observations from doing the investigation in a table like the one below.
Substance
Methylated spirits
Nail polish remover
Water
Ethanol
Boiling point (\(^{\circ}\)C)
\(\text{78.5}\)
\(\text{56.5}\)
\(\text{100}\)
\(\text{78.4}\)
Initial volume (ml)
\(\text{20}\)
\(\text{20}\)
\(\text{20}\)
\(\text{20}\)
\(\text{2}\) \(\text{min}\)
\(\text{4}\) \(\text{min}\)
\(\text{6}\) \(\text{min}\)