Crushing Chemistry
In chemistry we have been learning about the Kinetic Molecular Theory (KMT) and different gas laws! To learn the concept we completed a series of experiments. Different aspects of the Kinetic Molecular Theory and gas laws include pressure, temperature, volume, matter, and the amount of molecules. Today we’d like to focus solely on pressure, Charles’ law, and Boyle’s law.
Temperature changes the volume of gas. One experiment we did, Experiment 6, portrayed this concept well. It had the following procedure:
Pour 10mL of water in a clean, empty aluminum can.
Place the can on a hot plate, and bring the water to a rapid boil.
Use tongs to lift the can and immediately invert the can and plunge into a container of ice water.
We predicted that when the hot can was plunged in the ice water, the can would crush. Make your own prediction and then enjoy the following slow motion clip of the experiment to see what happened!
Was your prediction right?!? Ours was! After the experiment was conducted, it was obvious that once the can filled with boiling water was placed into the ice water, the can was crushed and the empty space inside the can decreased, making the can crumple. To explain what scientifically happened, the water changed to steam from the heat and the steam escaped the can, so there were fewer gas particles inside the can. By turning it upside down, the amount of gas in the can was held constant. The temperature decreased, so the steam changed to water and the water vapor particles slowed down and moved closer together needing less volume. The internal pressure decreased, and the external pressure crushed the can. This is a great visual to help show Charles’ Law and what happens to volume when temperature is changed. Check out this experiment done on a large scale by watching “Myth Busters Impossible Tank Car Implosion” by following the link below!
Another principle we learned is when the pressure on the interior is increased, there is less space, and when the pressure is decreased there is more space. A great experiment we conducted that shows both of these principles quite well was Experiment 8, another experiment we did that day, which had the following procedure:
Observe the size and shape of the marshmallow in the syringe. Plug the end with your finger.
Push in the plunger.
Pull the plunger out as far as possible without removing it.
We predicted that the marshmallow was going to get squished at the end of the syringe. Which looking back is not very scientific but what can we say, it was just a prediction. Why don’t you take a guess and then watch another sweet video to figure out what actually happened!
How’d your prediction turn out?? Were you close? Our group sure wasn’t. We predicted the marshmallow was going to get squished and that didn’t really happen at all! Instead, Boyle’s law was demonstrated and the marshmallow either inflated or deflated depending on if there was higher or lower pressure in the syringe. Want another great visual of this experiment? Check out this picture!
Charles’ gas law (the law of volumes) states that gases tend to expand in volume when heated (directly proportional). Experiment Six, where we boiled water inside a can them submerged it in ice water, portrayed this law because when the hot gas inside the can was shocked by the ice water it crushed, therefore losing volume and demonstrating that temperature and volume is a direct relationship. Boyle’s gas law (the pressure-volume law) states that with more volume there will be less pressure, so particles don’t collide as often (indirectly proportional). In the marshmallow experiment when pressure was added inside the syringe the marshmallow shriveled, and vise-versa. This portrayed Boyle’s law because when the marshmallow was shriveled (less volume) there was more pressure, and when the marshmallow expanded (more volume) there was less pressure. These experiments are simple and can be done at home! Comment below how they go for you!