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NOTES

NOTES. 3.3 Temperature Scales 3.4 Energy. Teacher Copy. There are 3 Temperature Scales to be familiar with:. Fahrenheit Celsius ( o C ) Kelvin (K). 1 o C and 1 K both measure the same amount of energy change. 1 o F measures a much smaller amount of energy change than the o C or the K.

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  1. NOTES 3.3 Temperature Scales 3.4 Energy

  2. Teacher Copy

  3. There are 3 Temperature Scales to be familiar with: • Fahrenheit • Celsius (oC) • Kelvin (K) 1oC and 1 K both measure the same amount of energy change 1oF measures a much smaller amount of energy change than the oC or the K In fact, for every 9oF there are only 5oC or Kelvin The word “degree” is not used with the Kelvin Scale

  4. You should know the following for both the Celsius and Kelvin Temperature Scales: Phase ChangeCelsiusKelvin Freezing/ melting point of water 0oC 273 K Boiling/ condensation point of water 100oC 373 K Celsius Scale the Celsius Scale was specifically designed to mirror the phase changes of water Kelvin scale was designed to mirror the kinetic energy (EK) of the particles of a substance – the less EK the lower the Kelvin temperature and vice-versa When there is NO MORE EK (no particle motion) the Kelvin scale reads 0 K - that point is absolute zero

  5. You should know how to convert Celsius Temperatures to Kelvin Temperatures and vice-versa: ConversionFormulaExample Celsius to Kelvin oC + 273 100oC + 273 = 373 Kelvin Kelvin to Celsius K – 273 373 K – 273 = 100oC Both the Fahrenheit and Celsius Temperature Scales have negative numbers – for example -20oC or -10oF The Kelvin Temperature Scale does NOT have negative numbers – there are NO negative temperatures on the Kelvin Scale The Kelvin Temperature Scale goes down to zero, 0 K, and no further - zero Kelvin is called absolute zero

  6. You should know exactly what it is that temperature is measuring: Temperature is a measure of the average EK of a substance The faster particles move the more often they ‘bump into’ each other – this transfers energy from one particle to another – this transfer of energy is known as heat – and it is this heat that is being measured by a thermometer As particles move faster more energy is transferred and temperature goes up As particles move slower less energy is transferred and temperature goes down It would be impossible to measure the energy being transferred between each and every particle of a substance – instead the thermometer is measuring the “average” energy transfer among all the particles

  7. ALL matter is made of atoms and ALL atoms are ALWAYS moving • Therefore, ALL atoms have kinetic energy, (EK) =the energy of motion • Atoms can lose EKin exothermic processes • When this happens the atoms slow down, object getscolder • Slow down enough = ‘freeze’ into position • Absolute Zero = ALL motion stops • Atoms can gain EK in endothermic processes • When this happens the atoms speed up, object gets hotter • Speed up enough = unfreeze and become liquid • Speed up more = lose contact with one another and become gas

  8. Chemical Kinetic Energy consists of: • Vibrating particles and bonds • Translational (straight-line) movement of particles • Torquing (twisting) movements of particles and bonds

  9. Chemical Potential Energy (EP) consists of: • Chemical bonds • The position of particles relative to one another • The amount of movement (EK) of the particles

  10. How can EK be considered EP? Moving atoms have the potential to transfer some or all of their energy to other slower moving particles Remember – the transfer of energy is called heat, or more formally – thermal energy

  11. How can Chemical EP be changed? • Chemical bonds • Break bonds = energy IN (resulting particle HIGER in ENERGY • Make bonds = energy OUT(resulting particle LOWER in ENERGY • Particle Position • Think of a house of cards – it takes energy to keep all those cards stacked in that precarious position – blow on the hose of cards and the energy is released as the cards fall to the table (resulting position of cards in LOWER in ENERGY than when they were stacked) • EK of the particles • Change the temperature by changing the thermal energy – as T↑ EK ↑ and as T↓ EK ↓

  12. How can Chemical EK be changed? By adding or removing thermal energy This can be done in many ways – in the lab the most common way to add thermal energy is with a Bunsen burner – anything that would increase the motion of the particles would increase the EK and vice-versa

  13. The sum of the EKand EPof ALL the atoms of an object is called that object’s internal energy • The more mass an object has the more internal energy it has and vice-versa • The faster an object’s atoms are moving the more internal energy it has and vice versa

  14. Which of the following has more internal energy? An Iceberg A boiling Cup of Coffee b/c has more mass

  15. Which of the following has more internal energy? 32 oz. of iced coffee 32 oz. of boiling coffee b/c atoms moving faster

  16. Most internal energy stays locked inside an object and it’s impossible to know how much total internal energy an object has…….however…..it IS possible to measure the averageEKportion of internal energy

  17. Temperature is a measure of the averageEKof all the atoms of an object • Temperature ↑ means EK↑ HOT • Temperature ↓ means average EK↓ COLD

  18. Which of the following has atoms with a higher average kinetic energy? An Iceberg A boiling Cup of Coffee higher temperature = atoms moving faster = higher average EK

  19. Which of the following has atoms with a higher average kinetic energy? 32 oz. of iced coffee 32 oz. of boiling coffee Higher temperature = atoms moving faster = higher average EK

  20. Which of the following has atoms with a higher average kinetic energy? 16 oz. of boiling coffee 32 oz. of boiling coffee same temperature = atoms of both moving at same speed = same average EK!!

  21. energy will always flow in a predictable direction between two object…. From the hotter (higher average EK) object ….. ….to the colder (lower average EK) object

  22. Which way will the energy flow? 0oC from the hand to the ice cube ≈ 37oC

  23. Which way will the energy flow? air = 42oC air = – 4oC From the air to the skin From the skin to the air

  24. Energy flowing between two objects which are not at the same temperature is given a special name….. ……….it is called Heat Energy or heat for short AKA: Thermal Energy

  25. The old-fashioned unit of energy is the calorie (cal) The food Calorie (Cal) is equal to 1,000 regular calories Note the capital C, which means 1,000 calories or 1 Kilocalorie Note the lower case c, which means just 1 calorie

  26. The calorie was later replaced with the SI unit of energy, the joule (J) 1 cal = 4.184 joules 1 joule is a VERY SMALL amount of energy It takes about 75,000 J just to heat a cup of tea

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