Download Notes on Heat, temperature and kinetic energy

Energy, Temperature, and Kinetic
Energy
States of matter
Solids

fixed volume and shape

particles are held tightly in place

particles vibrate slightly

not easily compressed
Liquids

fixed volume but not a fixed shape

particles slide past one another

only slightly compressible
States of matter
Gas

composed of neutral particles

neither fixed volume nor shape

particles constantly in motion at high speeds

easily compressed
Plasma

similar to gas except the particles are charged

most common state of matter in the universe
but rare on earth
Energy….
• …is the capacity to do work
• …is measured in Joules ( calories in the English
system)
• …is released when chemical bonds are broken and
stored when bonds are formed
• …comes in many forms including light, heat and
electricity, chemical, sound
Endothermic Processes
Involves the absorption of energy
Ex: melting of ice and evaporation
Exothermic Processes
Involves the release of energy
Ex: freezing of water and condensation of water vapor
Endothermic Reactions
• Endothermic reactions absorb energy from
their surroundings.
• If a substance is undergoing an endothermic
reaction would it’s surroundings usually get
warmer or colder? __________
• Endothermic reactions occur when the bonds
of a substance are broken.
Useful Endothermic Reactions
• Cooking is an endothermic reaction.
– The food takes in heat provided by the oven/stove.
– The chemicals of the food undergo a chemical reaction
making them easier to digest.
• Cold packs for sports injuries rely on endothermic
reactions.
– When you twist or shake the pack the chemicals in the
pack start reacting.
– When they undergo an endothermic reaction they take
heat in from their surroundings.
– This makes the pack cold.
Exothermic Reactions
• Exothermic reactions give off heat.
• They occur when chemical bonds are formed.
• If substances are undergoing exothermic
reactions will their surroundings get hotter or
colder? ____________
Useful Exothermic Reactions
• Combustion: all combustion reactions give off
heat.
• Neutralization (acid reacting with a base)
reactions are exothermic.
• Hand warmers
– When the hand warmer is shaken, chemicals
inside undergo an exothermic reaction
– This releases the heat which helps to warm
up your hand.
Laws of Conservation
• Law of Conservation of Mass states that
matter cannot be created or destroyed by
ordinary physical or chemical means.
• Law of Conservation of Energy states that
energy cannot be created or destroyed by
physical or chemical means but can be
changed from one form to another. (Also
known as First Law of Thermodynamics)
Examples of Transfer of Energy
• During photosynthesis light energy is converted
into chemical energy
• Activation of a light stick converts chemical energy
to light energy
• During digestion, food (stored energy) is
converted to chemical energy
• When a falling object (kinetic energy) hits the
ground some of the KE is converted to sound
energy and some to heat energy
Heat…..
• …. is the transfer of energy between objects that are at
different temperatures.
• …… is always transferred from the higher temperature object
to the lower temperature object. An object becomes cold as
heat is removed from it, not from the transfer of coldness to
the object. A cold object will still have some heat energy.
• …… is not the same thing as temperature.
What is heat measured in? _________
Temperature….
• …is the measurement of the average internal
kinetic energy of the particles of a substance
• ....increases when kinetic energy increases
• Kinetic energy is energy due to motion, so
when motion increases, kinetic energy
increases, thus temperature increases
Temperature Scales
• The English unit for temperature is Fahrenheit.
• In Science, we use Kelvin and Celsius (also
known as Centigrade) Scales
• Absolute zero (0 Kelvin or -273 ºC) is the
temperature at which all motion of particles
should hypothetically cease.
• The Kelvin unit does not use the degree symbol.
Temperature
Comparison
Boiling Point and Condensation Point of
water: 212 ºF or 100 ºC
Freezing Point and Melting Point of
water: 32ºF or 0ºC
Human Body Temp: 98.6ºF or 37ºC
Temperature Conversion
• To convert from Celsius to Kelvin, add 273.
• To convert from Kelvin to Celsius, subtract 273.
• Kelvin temps can not be negative.
Temperature Conversion
• Convert the following:
1. 43ºC = ________K
2. 367 K = _______ºC
3. -123º C = ______K
4. 198 K = _______ºC
5. 290ºC = _______K
6. -6 ºC = ________K
7. 12 K =________ºC
Temperature Conversion
• Convert the following:
1. 43ºC = __316_K
2. 367 K = __94_ºC
3. -123º C = 150 K
4. 198 K = _-75_ºC
5. 290ºC = _563_K
6. -6 ºC = _267__K
7. 12 K =_-261__ºC