Presentation on theme: "Gases, Liquids and Solids"— Presentation transcript:
1Gases, Liquids and Solids States of Matter, Chapter 10
2Describing a Gas A gas expands to completely fill the container. A gas can flow.A gas can be compressed.Between the particles of a gas there is empty space.
3Gas PressureGas pressure is the force exerted by a gas per unit surface area of an object.It is caused by gas particles colliding with an object.An empty space, with no particles and no pressure, is a vacuum.Atmospheric pressure results from air particles colliding with an object.
6Measuring PressureBarometer – device that measures atmospheric pressureInvented by Evangelista Torricelli in 1643The pressure was measured by finding the height of the Hg column (using the unit mmHg).
7Measuring pressure in a sample of gas: A manometer measures the pressure of a gas in a container.
8Units of Pressure:Metric unit of pressure is the pascal (Pa).A more familiar units include the atmosphere (atm) and the millimeter of mercury (mmHg).Know this:1 atm = mm Hg = torr = kilopascal (kPa)
9ObjectivesDescribe the nature of a liquid in terms of the attractive forces between the particlesDifferentiate between evaporation and boiling of a liquid
10A Model for LiquidsLiquid molecules are free to slide past each other, so liquids, like gases, can flow.Liquids take the shape of their container.Liquids are condensed, not compressible.
11VaporizationVaporization is the conversion of a liquid to a gas or vapor.If the conversion occurs at the surface of a liquid that is not boiling, the process is called evaporation.Evaporation is a cooling process. The particle with the highest kinetic energy tend to escape first, leaving cooler particles behind.
12Vapor PressureVapor pressure that results from the vapor particles colliding with the walls of the container.It is a force due to a gas above the surface of a liquid.(Vapor is the gaseous state of a substance that is a liquid or solid at room temperature).
14Equilibrium vapor pressure… When the rate of vaporization is equal to the rate of condensation, no net change in vapor pressure occurs.This is a dynamic equilibrium.
15Temperature affects the rate of vaporization Increasing the temperature of a contained liquid increases the vapor pressure over the surface of a liquid.
16BoilingBoiling occurs when the vapor pressure is equal to the external pressure.In Denver, where atmospheric pressure is low, boiling occurs at a lower temperature.In a pressure cooker, boiling occurs at a higher temperature.
17Boiling point… the temperature at which boiling occurs. Normal boiling point is the temperature at which boiling occurs at 1 atm pressure (normal pressure).Boiling is also a cooling process.
18The Nature of SolidsThe particles in a solid tend to vibrate about fixed points. They are not free to flow.Most solids are highly organized, dense and incompressible.
19Melting point…. the temperature at which a solid turns into a liquid. Solid liquidFreezing…Liquid solid
20Distinguish between a crystal lattice and a unit cell ObjectivesDescribe how the degree of organization of particles distinguishes solids from liquids and gasesDistinguish between a crystal lattice and a unit cellExplain how allotropes of an element differ
21Solids Crystal Unit cell Allotrope Amorphous solids (glass, soot) Several forms of an element (carbon)Amorphous solids (glass, soot)Supercooled solidsNetwork solids (diamonds, graphite)
22The Solid State: Types of Solids Crystalline solids
26Changes of state Solid to liquid… Liquid to solid… Liquid to gas… meltingLiquid to solid…freezingLiquid to gas…boiling, evaporatingGas to liquid…condensationSolid to gas…sublimationGas to solid…deposition
27Phase diagramsA phase diagram is a graph showing the relationship between pressure and temperature for solid, liquid and gas states of a substance.Triple point describes the set of conditions where all three phases, solid, liquid, and gas, can exist in equilibrium with each other.
30Note:The solid-liquid equilibrium line for CO2 has a negative slope, while the solid-liquid line for water has a positive slope.This shows that increasing the pressure on a solid sample of water can cause the solid to melt, while a solid sample of CO2 would remain a solid.This unique property of water allows a skater to glide over the surface of ice on a layer of water under their thin skate blades.
31Heating curveA heating curve shows the relationship between temperature and time as heat is added to a system.Notice that as a phase change occurs, even though heat is being added, no change in temperature occurs.