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# MU PHY 182 - Intro to temperature and pressure

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PHY 182 1st Edition Lecture 1 Outline of Current Lecture I.Understanding PressureII. The three states of matterIII. Atoms and MolesIV. Temperature and Phase ChangesCurrent LectureUnderstanding Pressure- Pressure - the ratio of the force to the area on which the force is exerted (P=F/A)- Pressure is a scalar, not a vector.- The SI unit of pressure is a Pascal, defined as 1Pa=1N/m^2.- Note that gravity affects the pressure of fluids (liquids and gases). This effect is much more noticeable in liquids than in gases.- In many practice problems, the environment in which the scenario takes place will be a vacuum, which means it is an enclosed space in which the pressure is approximately 0 Pa.- Standard atmospheric pressure is defined as 101,300 Pa or 1atm.The Three States of Matter- The three states of matter that will be dealing with are solids, liquids, and gases.- The change between two different states of matter is known as a phase change.- State variables are parameters used to describe a macroscopic system (volume, pressure, mass, thermal energy, etc.)- Δ is the Greek letter delta, it means a change in valueAtoms and Moles- 1 mole is equal to 6.02x10^23 atoms or molecules, this number is known as Avogadro's number.- To find the number of moles in a particular substance, divide the number of particles in the substance and divide by Avogadro's number.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- A value you may need to know how to calculate is number density. This is found by dividing the number of atoms within a substance by its volume- Molar mass is also an important quantity. It is equal to the mass of 1 mole of a substance.Temperature and Phase Changes- There are a few different temperature scales that you may encounter. In physics, you will be using Celsius and Kelvin. To convert from Celsius to Kelvin, add 273 to the temperature in Celsius. (Kelvin temperature=Celsius temperature + 273)- On the Kelvin scale, absolute zero is 0K. Absolute zero is defined as the temperature at which the internal energy of a substance is zero.- Examples of phase changes include: melting, freezing, condensation, and boiling- A system at its melting point is said to be in phase equilibrium, which means that any amount could be solid and any amount could be liquid.- For a substance to experience a phase change, it must increase or decrease its thermal energy (and thus, its temperature)- Phase diagrams are often used to show how the phases of a substance vary with both temperature and

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