Remembering magnitudes and units In this unit well use these units, you must learn them by heart MAGNITUDE UNIT SI Remember Kg MASS 1 Kg = 1000 g (kilograme) 1 m3 = 1000 L VOLUME m3 1 L = 1000 mL (cubic meter) 1 L = d m3 1 cm3= 1 mL Pascal 1 atm = 101300 Pa PRESSURE (Pa = N/m2) 1 atm = 760 mm Hg KTEMPERATURE T( K ) = T (º C) + 273 (Kelvin)
Properties of matter● Matter has two kinds of properties: – General properties: they are common to all kinds of matter: ● mass, volume, temperature,... – Specific properties: they are different for every kind of matter: ● Melting temperature, boiling temperature, density, electric conductivity,...
Macroscopic behaviour Macroscopic properties of solids, liquids and gasses. SOLID LIQUID GASIt has its own shape It adapts to the shape of its container It is not easily compressible It is easily compressible. It doesnt flow It flows It flows It tends to fill all aviable spaceIt has its own volume It has its own volume Any two gasses are mixed easily
Kinetic Theory● The kinetic theory explains the behaviour of solids, liquids and gasses.● Its based on three ideas: – Matter is made of particles – The particles are in continuous motion: ● Temperature is a measurement of the average kinetic energy of the particles. ● If the system is hotter, its particles move faster – All particles attract each other with a force.
Kinetic Theory MICROSCOPIC BEHAVIOR OF THE DIFFERENT STATES SOLID LIQUID GAS The only possible Every particle can Every particle has a Particles motion movement is slide over its uniform rectilinear vibration neighbours motion Every particle is in Every particle is in The distance is muchDistance between contact with its contact with its bigger than particles particules neighbours neighbours size There are almost no Atractive force Very strong forces Weak forces forces betweenbetween particules particles
Kinetic Theory and solids● These questions about solids can be answered using the kinetic theory: – Why do solids keep their own shape? – Why do solids increase their volume when they are heated? – Why do solids became liquids when their temperature increase enough? – Why cant solids be compressed?
Kinetic Theory and liquids● These questions about liquids can be answered using the kinetic theory. – Why can they flow? – Why cant they be compressed? – Why do liquids increase their volume when they are heated?
Kinetic Theory and gasses● The temperature is related to the average kinetic energy of the particles of a system. – If the temperature raises, the particles move faster.● Gasses exert pressure on the container walls: – Pressure is a consequence of the collision of particles with the container walls.
Kinetic Theory and gasses● A few questions that we can answer with the kinetic theory (I): – Any two gasses can be mixed together. Why? – Why can gasses be compressed easily? – Why can gasses flow? – ...
Kinetic Theory and gasses● A few questions that we can answer with the kinetic theory (II): – ... – Does pressure change when a gasses is heated? How? Why? – Does pressure change when we reduce the volume of the container of a gas? How? Why? – Why do gasses tend to fill all available space?
Gasses Laws● Charles Law: describes how gasses expand when heated.● At a constant pressure, the volume of a gas increases or decreases proportionally to its absolute temperature. – Dont forget: T(K) = t(ºC) + 273 V = constante T V1 V2 = T1 T2
Gasses Laws● Charles Law ● Use the Internet for more information: ● Practise doing numeric exercises about this law: http://www.educaplus.org/gases/e ● A simple experiment about Charles Law http://youtu.be/ATje2S5YZNo ● An interactive on-line software about Charles Law http://www.educaplus.org/gases/fl
Gasses Laws● Gay-Lussacs Law: describes the relationship between pressure and temperature in gasses contained in rigid containers (V = constant)● At a constant volume, the pressure of a gas increases or decreases proportionally to its absolute temperature. Dont forget: T(K) = t(ºC) + 273 p = constant T p1 p2 = T1 T2
Gasses Laws● Gay-Lussacs Law ● Use the internet for more information: ● Practise doing numeric exercises about this law: http://www.educaplus.org/gases/e ● A simple experiment about Gay-Lussacs law: http://youtu.be/VNU6YpKmLtM
Gasses Laws● Boyle-Mariotes Law: describes how gasses are compressed.● At a constant temperature, the pressure and the volume of a gas are inversely proportional. p · V = constant p1 · V 1 = p 2 · V 2
Gasses Laws● Boyles Law ● Use the internet for more information: ● Interactive on-line software about this law: http://www.educaplus.org/gases/fl ● A experience about this law: http://youtu.be/J_I8Y-i4Axc ● Practice doing exercises about this law: http://www.educaplus.org/gases/e
Gas Equation● The three laws we saw before can be reduced to an only equation: the gas equation● We must use it if p, T and V change at the same time. Be careful: T must be expressed en Kelvin p·V = constant T p1 · V 1 p 2 · V 2 = T1 T2
Changes of State● All matter can move from one state to another.
Changes of state● Sometimes matter absorbs energy when its state changes (progressive changes of state) – (Graph: from left to right)● In other occasions, matter gives off energy (regressive changes of state) – (Graph: from right to left)
Changes of state.How Kinetic Theory explains them ● When a solid is heated up its particles move faster. ● The forces between particles cant keep them vibrating around fixed positions. ● The particles can now See in the internet slide past one other. ● The solid becomes a liquid.
Changes of state.How Kinetic Theory explains them ● When a liquid is heated its particles move faster. ● The forces between particles cant keep themselves together. ● The particles can now separate each other. See in the internet ● The liquid becomes a gas.
Changes of state. Evaporation and boiling● Vaporisation can happen in two different ways. There are two ways of changing liquid into a gas: – Evaporation: the particles that are the nearest the surface are weaklier united to its nearby particles. They can separate from the others more easily. – Boiling: if the motion of particles is fast enough, all particles can separate from each other.
Changes of state. Evaporation and boiling● There are two main differences between both of them: – Evaporation occurs only in the surface of the liquid and boiling takes place in inside the liquid (bubbles of gas appear and go up to the surface of the liquid). – Boiling happens at a specific temperature (boiling point), there are not a specific temperature for evaporation
Changes of state Heating curve ● When we heat a solid, its temperature changes with time as we can see in the graph ● The temperature keeps constant during every change of state. ● Tf: melting point: The system can be solid, liquid or a mixture of both. ● Te: boiling point: The system can be liquid, gas or a mixture of both.
Changes of state Cooling curve ● When we cool a gas, T keeps constant at boiling and melting points. ● Tf: melting point: – The system can be solid, liquid or a mixture of both. ● Te: boiling point: – The system can be liquid, gas or a mixture of both.
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