The Particle Model & Changes of State Topic 5

Heat Capacity Capacity the ability to receive or contain: This hotel has a large capacity. the maximum amount or number that can be received or contained; cubic contents; volume: The inn is filled to capacity. The gasoline tank has a capacity of 20 gallons.

Heat Capacity The amount of thermal energy (heat) that warms or cools an object by 1˚C It describes a particular object It depends on the mass of an object and the material it is made of Heat Capacity

Specific Heat Capacity The amount of thermal energy (heat) that warms or cools 1g of a material by 1˚C It describes a specific material It depends only on the material the object is made of Specific Heat Capacity

Specific Heat Capacity

Heat Capacity

Think About it! Do you think it is possible to boil water in a plastic bag? Survival 101

Changes of State As particles speed up and slow down, they will change state after a certain point Solid  Liquid  Gas Ice  Water  Steam

Changes of State freezing

Changes of State Different substances require different temperatures or amounts of pressure to change state Changes of state are reversible under the right conditions Baking a liquid batter into a solid cake is not a change of state, it cannot be reversed

Melting & Boiling When energy is added to a substance the particles speed up Melting is a solid to a liquid Ice to water Boiling or Evaporation is a liquid to a gas Water to steam

Melting & Boiling All pure substances have melting and boiling points (p.221) Many substances have combustion points that prevent melting – like wood Most substances are gases or solids at regular atmospheric temperatures Many substances are not stable in liquid state

Melting & Boiling Points

Condensation & Freezing When energy is removed from a substance the particles slow down Condensation is a gas to a liquid Drops of water forming on the outside of a cold glass Freezing is a liquid to a solid Water to ice

Sublimation & Deposition When a substance is unstable as a liquid it may change state from solid to gas and gas to solid A solid to gas is Sublimation Dry Ice to gas A gas to a solid is Deposition Water vapor to frost on a window

Liquids Particles in liquids move very quickly As high energy particles escape the liquid, the average energy decreases, cooling the liquid

Liquids Evaporation cools the surface the liquid is on This process is called evaporative cooling Evaporative cooling is useful for: Joggers cooling as sweat evaporates Water cooling a roof on a hot day A wet cloth on a forehead for a fever Kangaroos BUT: Hypothermia can happen because of it!

Changes of State Super-cooled Beer

Transferring Energy Topic 6

Energy Transfer Energy can be transferred 3 ways: Radiation Conduction Convection BY SONG!

Radiation This is the transfer of energy without the movement of particles This is also called Electromagnetic Radiation (EMR) Radiant energy travels in waves It can pass through space, air, glass and many other materials

Radiation – EMR Spectrum

Radiation All radiant waves travel very fast across empty space – at 300million m/s Radiant energy travels in a straight line Most radiation that we are exposed to is natural. Slip Slop Slap Radiation (the radioactivity) can be detected, measured and controlled

Radiation Light waves and radiation waves will travel until they hit something that will: Absorb Let the radiation get part way into an object, often as heat Transmit Allow the radiation to pass through, without absorption Reflect Cause the radiation to bounce off

Radiation - Absorption Dark coloured surfaces: absorb radiant energy when they are cool give off radiant energy when they are hot Light coloured or shiny surfaces do not effectively absorb or give off radiant energy Can you think of animals adapted with this in mind?

Radiation - Absorption Radiant emission (giving off) of energy depends on surface area Animal adaptations show this: Desert animals have large ears to release heat Killer whales have simple bodies and small limbs to keep heat in Polar bear has black skin to absorb radiant energy with transparent hair that transmits ultraviolet radiation to the skin

Conduction Conduction is the transfer of energy through solids Direct collisions between particles pass energy through the objects The space between particles in a solid determines how fast energy is conducted

Conduction Metal particles are often very close together, they conduct well Wood, plastic and glass particles are further apart and are poor conductors – called insulators A metal wire will conduct, but is wrapped in plastic to insulate it

Convection The transfer of energy in fluids It follows a circular pattern called a convection current As fluid particle heat up, speed up, and spread apart, they become lighter and rise Once further from the heat, the particles cool and fall

Convection Convection in the atmosphere causes thermals which birds and gliders use to soar, they also cause turbulence on planes Convection ovens cook more evenly by circulating heat

Convection Currents

Convection Currents

REMEMBER: Energy can be transferred 3 ways: Radiation Conduction Convection BY SONG! Heat energy always flows from the warmer to cooler object or substance

Think About it! Conservation of Energy Energy cannot be created or destroyed Energy can only be transformed from one type to another, or passed from one object, or substance, to another Turn to p.232: follow the transfer of energy

Energy Transfer Energy in her fist transferred to the ball The ball transferred energy to the floor. Conduction occurred, when the energy in her fist was conducted by the particles in her fist to the particles in the ball. The particles in the ball conducted the energy to the particles in the floor. The particles in the air were also warmed by the flight of the ball and the particles transferred this energy by convection currents which were created in the air. CREATE AN ENERGY FLOW SYSTEM

Energy Systems All Energy Systems have 5 features: Energy Source Energy can be mechanical, chemical, radiant, nuclear or electrical Direction of Energy Transfer Energy moves from high to low concentration Transformations Energy changes form as it is transferred Waste Heat Most energy is transferred, but some is always lost to surroundings Control Systems A device to start and stop the transfer of energy