Water acts like a solvent to very many things and is the basis for many chemical and physical interactions that we depend on every day. Oil is one exception to this.
- Always Preform Experiments Under Adult Supervision!
- Wear Safety Glasses and Gloves!
- Always Read and Understand Instructions Before You Begin!
- Only Perform Experiments In A Clean Safe Workspace!
What This Experiment Will Demonstrate:
That water and oil will not mix under normal circumstances and how we can alter the mixture to make the two blend.
- A Clear Glass or Plastic Container With a Lid
- Cooking Oil
- Liquid Dish Soap
- Optional – Food Coloring
Set Up: Fill the container about 1/3 full of water. If you want to, add a few drops of food coloring to the water. Carefully add cooking oil until the container is 2/3 full and then put on the lid.
Prediction: What do you think will happen when the water and oil are shaken? Will they mix? Will they stay apart? Write down your predictions to check at the end.
Procedure: Make sure that the lid is on tight and then shake the container hard for thirty seconds. Set the container down and watch what happens. After the oil and water separate and settle take off the lid and add a little dish soap. Put the lid back on and shake the container again for 30 seconds. Set the container down and observe what happens this time.
Results: The oil and water from the first trial quickly separate, but in the second trial the dish soap caused them to mix and stay mixed.
What Happened: Water is a “polar” molecule. That means it has one side with a negative charge and another with a positive charge this makes water very good at dissolving other molecules that have positive or negative charges ‘Hanging Out’. Sugar and Salt are both molecules that dissolve rapidly in water. Oil on the other hand is made of long chains if carbon atoms bound to hydrogen in a way that makes them non-polar and ‘hydrophobic’ (water hating). As a general rule only polar substances dissolve in polar solvents and non-polar solutes only dissolve in non-polar solvents.
The soap we added in the second part of the experiment acted as an emulsifier. An emulsifier is a molecule with two end one that is hydrophilic (water loving) and the other is hydrophobic (water hating). These molecules attach one end to oil and one to water and cause them to mix together.
Real World Application: There are many times in cooking and cleaning that we need oil and water to mix. When you are washing your hands or washing the dishes the soap helps oil and other compounds to mix with water so they can be rinsed away. In cooking and baking oil and water are often used in the same recipe and the food would turn out poorly if they separated, but you would not like soap I your food so most propel use eggs to help oil and water stay mixed together. Depending on what type of product or process that needs oil and water to mix there are many specialized emulsifiers.
Additional Study and Resources:
Projects Using This Effect