Question

Rationalize the following observations. a. Aerosol cans will explode if heated. b. You can drink through a soda straw. c. A thin-walled can will collapse when the air inside is removed by a vacuum pump. d. Manufacturers produce different types of tennis balls for high and low altitudes.

Short answer

Aerosol cans explode when heated due to an increase in pressure inside the can caused by the ideal gas law. Drinking through a straw is possible because suction creates a pressure difference that pushes the liquid up the straw. A thin-walled can collapses when air is removed due to the external pressure overwhelming the reduced internal pressure. Different tennis balls are produced for high and low altitudes to compensate for changing air pressure and density, ensuring consistent gameplay.

Step-by-step solution

Observation a: Aerosol cans will explode if heated.

This observation can be explained using the ideal gas law equation, \(PV = nRT\), where P represents pressure, V represents volume, n represents the number of moles, R represents the ideal gas constant, and T represents temperature. When an aerosol can is heated, the temperature (T) inside the can increases. Since the volume (V) remains constant and heat adds energy to the molecules in the gas, the pressure (P) inside the can must increase. If the pressure becomes too great for the can to handle, the can explodes.

Observation b: You can drink through a soda straw.

The process of drinking through a straw is related to the pressure difference created when suction is applied. When we suck the air out of the straw, we reduce the air pressure inside the straw. As the atmospheric pressure outside the straw is greater than the pressure inside the straw, this creates a pressure difference that pushes the liquid up into the straw and eventually into our mouth.

Observation c: A thin-walled can will collapse when the air inside is removed by a vacuum pump.

When the air inside a thin-walled can is removed by a vacuum pump, it lowers the internal pressure of the can, causing it to become significantly lower than the atmospheric pressure outside the can (as observed in the soda straw explanation). Consequently, the greater external pressure applies force on the thin walls of the can from all directions, causing them to buckle and eventually collapse inwards.

Observation d: Manufacturers produce different types of tennis balls for high and low altitudes.

The reason behind producing different types of tennis balls for different altitudes lies in the change of air pressure and air density with altitude. At higher altitudes, air pressure and air density are lower than at sea level. As a result, a tennis ball used at higher altitudes will experience less air resistance, causing it to travel faster and bounce higher. To compensate for these conditions, manufacturers produce tennis balls with a lower internal pressure for use at high altitudes, preventing them from bouncing too high and allowing for more consistent gameplay. Conversely, tennis balls with a higher internal pressure are produced for use at lower altitudes where air pressure and density are greater.

Key concepts

Gas Pressure

When discussing the behavior of gases under various conditions, understanding gas pressure is fundamental. Gas pressure is the force that a gas exerts on the walls of its container per unit area and results from the collision of gas particles with the walls. This concept is crucial when we explore everyday phenomena, such as why aerosol cans might explode when heated. According to the ideal gas law, \(PV = nRT\), pressure (P) is directly proportional to temperature (T) when the volume (V) is fixed. So, as the temperature rises, the gas particles move more rapidly, collide with the walls more frequently and with greater force, leading to an increase in pressure. This increase in pressure can result in a can's explosion if the pressure exceeds the can's ability to contain it.

Moreover, understanding pressure is essential when considering drinking through a soda straw. Creating a pressure differential by sucking air out from a straw lowers the pressure inside it, causing the atmospheric pressure to push the liquid up and into our mouths. Similarly, a vacuum pump can cause a thin-walled can to collapse due to the significant pressure difference between the inside and outside of the can. In physical chemistry, we use these principles to predict and explain the behavior of gases in both theoretical and real-world applications.

Chemical Principles

Chemical principles are the fundamental concepts that underlie the behavior of matter, particularly atoms and molecules, including reactions, energy changes, and interactions. These principles guide us to understand the molecular level changes when dealing with different physical states or chemical reactions. For example, when a thin-walled can collapses under the influence of a vacuum pump, it's the principles of gas behavior and pressure differences that explain the phenomenon. The removal of air reduces the number of gas molecules inside the can, decreasing the internal pressure. As per Boyle's law, when the volume is constant, the pressure is inversely proportional to the number of gas molecules. Therefore, a lower number of molecules means less pressure, which can't counteract the atmospheric pressure, resulting in the collapse of the can.

Chemical principles also play a role when manufacturers create tennis balls for different altitudes. The air's chemical composition affects density and pressure, and therefore, how the tennis ball performs. Thus, an understanding of these principles allows manufacturers to alter the balls' internal pressure to ensure consistent performance under varying atmospheric conditions. This is a crucial aspect of chemical engineering applied within the realm of sports technology.

Physical Chemistry

Physical chemistry is the branch of chemistry concerned with the study of how matter behaves on a molecular and atomic level and how chemical reactions occur. It combines principles from physics and chemistry to explain the physical properties of molecules, the forces that act upon them, and the way they interact and combine. One core aspect of physical chemistry is the study of thermodynamics, which explains heat transfer and the resultant changes in temperature, volume, or pressure of a system. This is evident in our example of an aerosol can, where thermodynamics principles predict the increase in pressure due to temperature rise which can lead to an explosion if not controlled.

Physical chemistry also helps to understand how gas molecules move and interact with their environment, such as why tennis balls are affected differently at various altitudes and need adjustment for optimal performance. By blending real-world observations with theoretical laws from physical chemistry, we can predict and manipulate matter's behavior to suit our everyday needs and innovations in technology and materials science.