How are gases different from solids and liquids?

What is pressure? -start by asking students: you guys looked at different properties of gases and how they behave in different scenarios, or under different conditions. What type of properties were you guys looking at (Chemical or Physical)? Physical -So today we are going to talk about pressure, what it is, and why it might be important to understand if we are to make a case for understanding or doing inquiry into atmosphere. SO first, what do you THINK pressure is—who can define it?

Pressure: the amount of force applied over a given area Force = weight Area = size of a surface or amount of space the surface of an object takes up Area = length x width

Pressure is a mathematical relationship Pressure = _Force_ Area P = __F__ A As amount of force applied increases, pressure increases (Direct Relationship) As area increases, pressure decreases (Inverse Relationship)

Which would you rather be stepped on by? Why?

Gas molecules exert pressure on the walls of their container List at least one piece of evidence of that you observed of this during the lab. How do you know? TPS: have student write evidences on slide/notesheet

Standard Unit for force = Newton (N) Force is a function of mass and gravity Standard Unit for area = Meters Squared (m2) A wireless mouse, a medium-sized apple, and a stick of butter each exert about 1N of force.

Standard Unit for pressure = Pascal (Pa) 1Pascal = 1N of force exerted over an area of 1m2 1Pa = pressure exerted on a slice of bread by a thin layer of butter Other units for pressure: pounds per square inch (psi), millimeters of mercury (mmHg), atmospheres (atm), kiloPascals (kPa)

International System of Units (SI) Base units: express one measurement (Ex: length, mass) Derived units: combine two or more base units (Ex: density, pressure)

Units for Pressure – must be able to use all (conversion factors!) 1 atm = 760 mmHg = 101.3 kPa 1 kPa = 1000 Pa 1lb/in2 = 6,894 Pa

Is each brick exerting the same total force on the ground? Explain.

To Do: Due at end of the period. 1) Complete A.3 Applications of Pressure (#1-4) 2) Read A.4 - (Atmospheric Pressure: pressure exerted by weight of the atmosphere) 3) Choose two investigations from the A.1 Properties of Gases Lab and explain how they showed the effects of atmospheric pressure.