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: 1.43 º C = ________K K = _______ º C º C = ______K K = _______ º C º C = _______K 6.-6 º C = ________K 7.12 K =________ º C

Temperature Conversion Convert the following: 1.43 º C = __316_K K = __94_ º C º C = 150 K K = _-75_ º C º C = _563_K 6.-6 º C = _267__K 7.12 K =_-261__ º C