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Unit 3 Topic 5- Change of States. Heat Capacity v Specific Heat Capacity. Heat Capacity v Specific Heat Capacity. So how fast does an object heat up? . Changing of States. What does “changing of states” mean? When something goes from either solid/liquid/gas to another form solid/liquid/gas
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Unit 3 Topic 5- Change of States
Heat Capacity v Specific Heat Capacity • So how fast does an object heat up?
Changing of States • What does “changing of states” mean? • When something goes from either solid/liquid/gas to another form solid/liquid/gas • Water is a great example… • It can melt (solid ice can melt to liquid water) • It can freeze (liquid water to solid ice) • It can become a gas (from liquid water to water vapour - gas - when it is boiled)
Changing of States There is a change of state where it breaks the natural progression … hops from solid directly to gas This is known as sublimation • What does “changing of states” mean? • When something goes from either solid/liquid/gas to another form solid/liquid/gas • Water is a great example… • It can melt (solid ice can melt to liquid water) • It can freeze (liquid water to solid ice) • It can become a gas (from liquid water to water vapour - gas - when it is boiled)
Change of State • Any pure substance can exist in all 3 states • Often easier said than done but it is doable • Time for a review! • Find a partner • Write “Thermal Energy” & “Temperature” & “Energy” on a piece of paper and … • … explain to me the difference between them!
Thermal vs. Temperature Review • Simply put, heat is the flow of thermal energy. • Temperaturerepresents average thermal energy. Heat goes from objects with high temperature to low temperature, not high thermal energy to low thermal energy. (Like diffusion) • For example, a massive glacier will have more total thermal energy than a small hot nail (simply because it has more molecules); however, its temperature is lower because it has less average thermal energy. Therefore, energy will be transferred from the nail to the glacier... • Thermal energy is the total internal energy of the system. i.e. how fast the molecules are vibrating
Evaporation • When you sweat you tend to cool off … why? • Enter Particle Model • Imagine a liquid (we will use water) in a jar … Top = moving fast (enough to escape) Middle/Lower = slower moving particle stay in liquid state WHAT?! That means what is left is cooler … Slower moving = lower temperature
Evaporation • When you sweat you tend to cool off … why? • Enter Particle Model • Imagine a liquid (we will use water) in a jar … Top = moving fast (enough to escape) Middle/Lower = slower moving particle stay in liquid state This is known as… Evaporative Cooling That means what is left is cooler … Slower moving = lower temperature
Examples of Evaporative Cooling • Joggers feel cold as their clothes dry out after a rain storm • Home owners spray water on the roof to cool house in hot some day • First aid worker puts a cool cloth on your head
Examples of Evaporative Cooling • During a change of state (phase) the total energy of a substance … • Increases or decreases • Why? • They don’t change speed they change state
Unit 3 Topic 6- Transferring Energy
Transferring Energy • You hold your hand beside a light bulb … your hand warms up – why? • The light bulb is an energy source • An object or material that can transfer its energy to other objects
Transferring Energy - Radiation • The sun shines billions of kms away but we feel it • Energy is transferred even though no material has travelled from the sun to us, solar cells, etc… • What is this transfer called? • Radiation • Transfer of energy without any movement of matter • Energy transferred this way is called Radiant Energy or Electromagnetic Radiation (EMR)
Transferring Energy - Radiation • EMRs can travel through all kinds of material and they have some unique characteristics … • Behave like a wave • Absorbed & Reflected by objects • Travel really fast (300,000 km/s) • Colours play a role in absorption / reflection of heat radiation (heat waves) • Dark colour absorb • White colours reflect
Transferring Energy - Conduction • Conduction is the transfer of energy when particles collide • Simply put … direct contact • To do this we need two different types of materials • Conductors … most metals as they carry a current or heat well throughout their entire material • Insulator … these are poor conductors such as wood or glass so they are good at trapping heat/cold and preventing it from escaping
Transferring Energy - Convection • Convection is the movement of particles (typically in fluids) carrying its thermal energy with it as it moves • Can create a current … how? • Heat rises, cools off, drops back down, heats back up and rises again, repeat … • Warmer solutions/particles are less dense • Cooler solutions/particles are more dense • Dense = amount of matter/particles in a solution
Transferring Energy - System • Energy Source – The part of the system that supplies the energy to the system • Direction of Energy Transfer – Always transferred away from the concentrated source • Energy Transformation – Not created or destroyed but transferred from place to place
Transferring Energy - System • Waste Energy – Little amount of thermal energy lost to surroundings not involved directly in the transfer • Control System – What controls the energy transfer
Unit 3 Topic 7- Thermal Energy Sources
Thermal Energy • Think back … what is thermal energy? • Correct • Energy generated by the movement or vibration of particles • That being said there must be a whole bunch of different sources! • Oh yes … yes there are!
