Oct. 22-26

In chemistry this week, I learned about expansion, contraction, and the relationship between pressure, volume, temperature, and the number of particles.

On Monday, I was reviewing with my class the ethanol and water experiment–both were heated on a machine over a certain amount of time and given energy through the process of heating–and why the ethanol in the tube rose while the water didn't. The answer is expansion. Expansion is when a liquid takes up more volume as its volume is increased by more energy input through heating. Therefore, expansion occurred in the ethanol while heating occurred. The heating caused the particles to spread out over a longer distance, therefore, causing the ethanol level to increase.


Throughout the week, we learned the opposite of expansion–contraction. Contraction is where the volume of a liquid is going down as a result of it cooling down. As the liquid cools down, the particles get closer and closer together. They don't spread out. Therefore, the volume goes down as the particles become more densely packed from cooling.

The connection between expansion and contraction is how they affect the overall density as well as volume of a liquid. Through expansion, the volume increases, meaning that the density is going to decrease since the number of particles and mass remain the same with increasing volume. As for contraction, the volume increases. Therefore, the density will increase since the number of particles and mass remain unchanged with a decreasing volume. Therefore, expansion and
contraction affect not only the volume
of a liquid, but also its density.


Yet, the heat could have caused the water to evaporate and perhaps the ethanol. However, both tubes had stoppers, thus preventing anything from entering or leaving the system. But, the question is: What prevented the liquid from coming out the tube? Well, I speculated that gravity and the attraction (suction) between molecules could have collided the air particles with the water particles. But, what really prevented the water from coming out the tube was pressure–as a pushing force between the air particles and the water particles. Pressure is the physical force exerted from one object onto another object, which can be represented by the formula: pressure=force/given area. In this case, the air particles exerted their physical force onto the water particles.

Pressure, though, is affected based on the force exerted onto the area, which means that the greater the area or volume, the less the pressure. If the area were less, though, then the pressure would be greater. Pressure is affected because the greater the area is, the greater the resistance to apply pressure is. Therefore, the pressure is less than if there were a lesser area that pressure would exert with less resistance.


Throughout the week, the focus was on pressure, volume, temperature, and the number of particles, which were utilized in four experiments including: volume vs. temperature, pressure vs. volume, number of particles vs. pressure, and the number of puffs vs. pressure.

The relationship between volume and temperature was a direct one. The greater the temperature was, the greater the volume. The reason for this is because the greater the temperature, the greater the energy input through the process of heating. This would cause the particles in a liquid to separate farther from each other, thus increasing the volume.

In this class, there were four experiments. My group and I did puffs vs. volume. During the experiment, we used 2 puffs for every mL. So, the data was this:

1/4 puff=228 k/Pa
1/2 puff=220 k/Pa
1 puff=116.14 k/Pa
3/2 puffs=69 k/Pa
2 puffs=63 k/Pa

Therefore, the relationship between Pa (pressure units) and volume is that the greater the number of puffs, the less the pressure. These findings make sense because the volume and pressure are inversely related. Therefore, the more the volume is, the less the pressure is.

Like the puffs lab, the pressure and volume were inversely related to one and another. The greater the volume is, the less the pressure is. This is so because the mass and
the number of particles
remain the same, so if
the volume increases,
then the pressure would
decrease.

The relationship between temperature and pressure is that since increasing temperature would increase the volume, then the pressure would decrease. Therefore, the more the temperature is, the less the pressure is.

The relationship between the number of particles and pressure was direct. Thus, the greater the number of particles is, the greater the pressure is.

However, temperature doesn't influence the number of particles and vice versa because temperature doesn't determine the number of particles. Nor does the number of particles determines the temperature.