The Ideal Gas Law: Crash Course Chemistry #12
Gas Behavior and Boyle's Law
The Ubiquity of Gas
- Gas is omnipresent, found in various forms such as in space, on Mars, and even dissolved in blood and soda.
- Despite its prevalence, gas behavior can often be overlooked; it interacts with our environment constantly.
Understanding Gas Behavior
- Gases are theoretically easy to describe when they behave predictably; however, they rarely do.
- The first mathematical relationship for gas behavior links pressure and volume, known as Boyle's Law.
Boyle's Law Explained
- Boyle's Law states that the product of pressure and volume remains constant if temperature and amount of gas are unchanged.
- Robert Boyle is credited with this law, but his work was significantly influenced by Richard Towneley’s contributions.
Historical Context of Boyle's Law
- Henry Power conducted experiments that were foundational to understanding gas relationships but received little recognition due to social hierarchies.
- The misattribution of credit highlights issues within scientific history regarding acknowledgment of contributions from less privileged individuals.
The Ideal Gas Law
Development of the Ideal Gas Law
- Over a century later, Jacques Charles and Amedeo Avogadro expanded upon earlier findings leading to the Ideal Gas Law.
- Charles established a relationship between volume and temperature at constant pressure; Avogadro linked volume with the number of moles under similar conditions.
Key Equation: P V = n R T
- The Ideal Gas Law combines these principles into one equation: Pressure times Volume equals the number of moles times a constant times Temperature (P V = n R T).
Understanding Variables in the Ideal Gas Law
- Each variable represents fundamental properties: pressure (force per area), volume (space occupied), number of moles (amount of substance), and temperature (thermal energy).
Pressure Measurement
Measuring Pressure
- Pressure is measured in pascals (Newtons per square meter); however, kilopascals or atmospheres are commonly used for convenience.
- One atmosphere is approximately equal to 101325 pascals but is often rounded to 100 kPa for simplicity.
Relationship Between Volume and Pressure
Understanding the Ideal Gas Law
Key Components of the Ideal Gas Law
- Definition of N: N represents the number of moles of gas in a system. A decrease in gas quantity leads to a decrease in both volume and pressure within a balloon.
- Universal Gas Constant (R): R is defined as 8.3145 liters kilopascal per kelvin mole, although it is neither universal nor constant, as will be discussed later.
- Temperature and Kinetic Energy: Temperature affects how we perceive heat; at an atomic level, it relates to kinetic energy—the speed at which particles move. An increase in temperature results in increased pressure due to more frequent collisions with container walls.
Demonstration of the Ideal Gas Law
- Experiment with Soda Can: The speaker demonstrates the Ideal Gas Law by boiling water inside a soda can, replacing atmospheric gas with water vapor. When exposed to ice water, rapid condensation occurs.
- Pressure Dynamics: As temperature drops significantly when exposed to cold water, both pressure and volume decrease. The external atmospheric pressure crushes the can due to low internal pressure.
Understanding Deviations from Ideal Behavior
- Ideal vs. Non-Ideal Gases: While understanding gases through the Ideal Gas Law is useful, not all gases behave ideally—especially under low temperatures or high pressures. This topic will be explored further in future discussions.
Important Terminology
- Standard Temperature and Pressure (STP): Defined as 0 degrees Celsius and 100 kilopascals; one mole of an ideal gas occupies 22.4 liters at STP.
- Absolute Zero: The theoretical temperature where all particle movement ceases, equivalent to zero kelvins or -273.15 degrees Celsius.
Conclusion Insights
- The episode emphasizes how various scientific thinkers contributed to formulating the Ideal Gas Law and highlights its practical applications for calculating any one variable if three are known.