Thermal Energy and Heat Matter

What is everything made of?

Atoms are incredibly small. They’re so small in fact, that in one drop of water there are… 1,700,000,000,000,000,000,000 atoms!

If that number of atoms were… sheets of paper, divided into a million equal piles, each pile would be so tall that it would stretch from the Earth to the Sun and beyond.

If that number of atoms were… pennies placed side by side, they would stretch for more than a million light years.

If that number of atoms were… Counted at a rate of one atom per second, for 48 hours per week, it would take the entire population of the world 10 million years to reach it T h e y’ r e p r e t t y s m a ll

Matter – anything that takes up space and has mass. It’s EVERYTHING!!

Particle Theory of Matter

Everything is made of particles (atoms)

Particle Theory of Matter Everything is made of particles (atoms) These particles are always moving

Particle Theory of Matter Everything is made of particles (atoms) These particles are always moving Each pure substance has it’s own type of particle

Particle Theory of Matter Everything is made of particles (atoms) These particles are always moving Each pure substance has it’s own type of particle When these particles gain energy, they move faster and need more space

Particle Theory of Matter Everything is made of particles (atoms) These particles are always moving Each pure substance has it’s own type of particle When these particles gain energy, they move faster and need more space

Particle Theory of Matter 1. Everything is made of particles (atoms) 2. These particles are always moving 3. Each pure substance has it’s own type of particle 4. When these particles gain energy, they move faster and need more space 5. When these particles lose energy, they move slower and need less space

Thermal Energy and Heat Expansion and Contraction

Question – What would happen to the atoms in a piece of matter if we heated it?

When objects are heated, the particles gain energy, move faster, and need more space so the object expands – increases in volume “gets bigger”

When objects are cooled, the particles lose energy, move slower, and need less space so the object contracts – decreases in volume “gets smaller”

Experiments Ball and ring

Balloon experiment

Engineers must think about expansion and contraction before they build things because if they didn’t, their structures would be destroyed. e.g. bridges, railway ties, teeth fillings, etc.

Special case - water Water is Weird !? Chemically speaking, water is very weird. It doesn't behave at all like it should. Ice shouldn’t float

Water is the only substance that expands as it freezes (it should contract!)

- question – In which season would you expect the telephone lines to sag the most? The least? Why?

Thermal Energy and Heat States of Matter

There are four states or phases of matter:

1. Solids – a solid has a definite shape and size (volume) -it’s particles are very close together and are moving (vibrating) very slowly. -(They have the least amount of energy)

2. Liquids – a liquid has a definite size (volume) but no definite shape. Liquids take the shape of whatever container they are in. It’s particles are further apart than in solids and are moving faster (have more energy)

3. Gasses – a gas has no definite size (volume) or shape. The particles will expand to fill any space they are in. The particles are the furthest apart and are moving the fastest (have the most energy)

4. Plasma – a high energy form of matter – it’s the only form of matter that gives off electromagnetic radation

Thermal Energy and Heat Changes of State

Solid Liquid Gas

Solid solidification Liquid Gas

Changes of State Solidification (freezing) – when a liquid turns into a solid (because the particles slow down and lose/release energy)

Solid solidification Liquid Gas

Solid solidificationfusion Liquid Gas

Fusion (melting) – when a solid turns into a liquid (because the particles gain energy and move faster)

Solid solidificationfusion Liquid Gas

Solid solidificationfusion Liquid condensation Gas

Condensation – when a gas turns into a liquid (because the particles slow down and lose/release energy)

Solid solidificationfusion Liquid condensation Gas

Solid solidificationfusion Liquid condensationevaporation Gas

Evaporation– when a liquid turns into a gas (because the particles gain energy and move faster)

Solid solidificationfusion Liquid condensationevaporation Gas

Solid solidificationfusion sublimation Liquid condensationevaporation Gas

Solid solidificationfusionsublimation Liquid condensationevaporation Gas

Sublimation – when a gas turns into a solid or a solid turns into a gas without turning into a liquid.

Thermal Energy and Heat Thermal Energy, Kinetic Energy, and Heat

Thermal Energy, Kinetic Energy, and Heat Kinetic Energy – the energy of moving particles.

The more kinetic energy something has, the warmer it feels – the more the particles move around, the more it expands.

The less kinetic energy, the cooler it feels, the more it contracts

Grab the metal leg of your chair – What does it feel like? Why? Touch your face with the same hand – what does it feel like?

Thermal Energy – the total kinetic energy (moving particle energy) of all of the particles in a substance

(a lake filled with freezing cold water has more thermal energy than a cup of boiling water because it has trillions times more particles.) Which would have more thermal energy? The ice sculpture has more energy – believe it or not

It takes twice as much energy to raise the temperature to 40 degrees because there are twice as many particles to be heated.

What is heat?

Heat – The transfer of thermal energy from one object to another because of a temperature difference Heat always travels “downhill” from high energy to low energy.

Assessment: Is any “heat” (thermal energy) transferred between two objects at the exact same temperature? Why would you freeze to death if you went swimming for 10 hours in 25 degree water in the middle of summer?

Thermal Energy and Heat Heat Travel

There are three ways that heat can travel:

1. Conduction – the transfer of thermal energy through a solid (by the collision of particles).

2. Convection – the transfer of thermal energy through a liquid or gas

3. Radiation – the transfer of thermal energy in the form of electromagnetic waves.

#1. Conduction In solids, particles are packed closely together As one particle is heated it gains energy, moves faster, and bumps into the other particles which transfers the energy. These collisions continue and the thermal energy is transferred through the solid object.

Which metal is the best conductor? Aluminum Brass Steel Copper Nickel

Best conductor

Thermal Energy and Heat Conductors and Insulators

Conductors and Insulators Most metals are excellent heat conductors (thermal energy easily passes through them). Copper was the best conductor of the metals we tested, but silver, gold and platinum are even better.

Fork and Match Experiment What do you think will happen when the flame reaches the fork?

Fork and Flame experiment

Screen and candle experiment

Other solids, however, are not very good at transferring thermal energy. These are poor heat conductors or heat insulators Some examples are glass, wood, styrofoam, pink insulation, goose down feathers, etc.

Conduction thawing pad Melt ice faster

Most insulators are used to slow down the transfer of thermal energy (i.e. they are used to keep objects warm or cold for as long as possible) like in a house.

Thermal Energy and Heat Convection

Why doesn’t conduction work as well in liquids and gasses?

2. Convection – the transfer of thermal energy through a liquid or gas In liquids and gasses, the particles are too far apart to collide with each other to pass on thermal energy by conduction. Instead, thermal energy moves in convection currents (which are flowing particles).

Experiment – Convection Box

Explanation the particles above the candle: 1. gain kinetic energy, 2. move faster, and 3. spread out which 4. makes the air less dense (lighter) so 5. it rises. 6. Cool, more dense air falls into the box to replace the warm air that rose.

Example – Candle or cup of hot water in front of a projector screen

Thermal Energy and Heat Radiation

Radiation? What do you think of when you hear the word radiation? What words pop into your head?

Radiometer Radiometer and heat lamp What do you think radiation is now?

3. Radiation – the transfer of energy in the form of electromagnetic waves Radiation can transfer energy through many different materials including empty space (a vacuum)

Electromagnetic Spectrum There are many different kinds of radiation:radiation:

All of these different kinds of radiation share three characteristics: 1. They all behave like waves 2. They can all be either reflected or absorbed by objects 3. They can all travel through a vacuum at very high speeds (the speed of light 300,000 km/sec)

When radiation is absorbed by an object, it causes the particles to move faster so they gain kinetic/thermal energy and they become warm. (Like in a microwave or when you sun bathe)

When radiation is reflected from an object, nothing happens to its particles they do not gain or lose energy. (like a mirror)