2 TEMPERATUREIs associated with heat but it is NOT HEAT. IT IS NOT A FORM OF ENERGY!!!!( Heat is)Review: What is KINETIC ENERGY?
3 KINETIC ENERGY (KE) Is associated with movement. If an object is moving fast has high KEIf an object is moving slowly it has low KE
4 TemperatureIn scientific measurements, the Celsius and Kelvin scales are most often used.The Celsius scale is based on the properties of water.0C is the freezing point of water.100C is the boiling point of water.
5 Temperature:A measure of the average kinetic energy of the particles in a sample. If an object is at HIGH temperature its particles are moving FAST At LOW temperature particles move SLOWLY
7 FIXED POINTS OF A THERMOMETER BOILING POINT OF WATERFREEZING POINT OF WATER
8 Temperature The Kelvin is the SI unit of temperature. It is based on the properties of gases.There are no negative Kelvin temperatures.K = C
9 TemperatureThe Fahrenheit scale is not used in scientific measurements.F = 9/5(C) + 32C = 5/9(F − 32)
10 2. SI unit for temp. is the Kelvin a. K = C (10C = 283K)b. C = K – 273 (10K = -263C)
11 DO NOWWhat is 35ºC in Kelvin?What is 10 K in ºC?
12 What is the temperature of the beakers? Which one needs more heat to boil?What is the difference between heat and temperature?
13 What is the relationship between heat and temperature?
14 1. Temperature is the average kinetic energy of the particles in a substance.
15 Heat and TemperatureThe temperature of an object tells us how HOT the object is. It is measured in degrees Celsius - °C, with a thermometer.Temperature is NOT a form of energy.HEAT IS A FORM OF ENERGY!!!
16 So how temperature and heat are related? Temperature is NOT the same as HEAT ENERGY although the two quantities are related.
17 They are both a the same temperature. Which contains more heat?
18 Types of energyPOTENTIAL ENERGY :STORED ENERGY. The energy inside the substance.KINETIC ENERGY : Associated with motion.Average KE = TEMPERATURE
19 HEATThe form of ENERGY that flows between two samples of matter due to their difference in temperature.It is measured in Joules. Other units are calories and kJ.It cannot be measured directly!
20 Heat always flows from warmer (HIGH T) to cooler(LOW T) objects. Cup gets cooler while hand gets warmerHeatHeat always flows from warmer (HIGH T) to cooler(LOW T) objects.Ice gets warmer while hand gets cooler
21 Energy The ability to do work. Energy is measured in Joules (J) Any change re quires energy. Changes can be Exothermic or EndothermicExothermic changes- release or give off heat while they occur. (condensation, freezing)Endothermic changes Absorb heat as they occur (melting, boiling)
22 ENERGY AND CHEMICAL REACTIONS EXOTHERMIC REACTIONS: reactions that RELEASE heat as they occur. Example: any combustion.ENDOTHERMIC REACTIONS: reactions that ABSORB heat energy as they occur.
23 Heating and CoolingIf an object has become hotter, it means that it has gained heat energy.If an object cools down, it means it has lost energy
24 a. Some things heat up or cool down faster than others. 6. Specific Heata. Some things heat up or cool down faster than others.Land heats up and cools down faster than water
25 HEAT CAPACITYThe amount of heat needed to increase the temperature of a material by 1oC. It depends on the MASS and the CHEMICAL COMPOSITION of the material.
26 SPECIFIC HEAT CAPACITY The amount of heat needed to increase the temperature of 1 g of substance by 1 C.Depends only on the chemical composition.
27 SPECIFIC HEAT CAPACITY MATERIALSPECIFIC HEAT J/g CWater4.18Alcohol2.43Aluminum0.90Iron0.45Lead0.13Sand0.83
28 Why does water have such a high specific heat? water metalWater molecules form strong bonds with each other; therefore it takes more heat energy to break them. Metals have weak bonds and do not need as much energy to break them.
29 Q = m x T x Cp Q = HEAT m = mass of substance How to calculate changes in HEATThe heat absorbed or released in a chemical reactionQ = m x T x CpQ = HEATm = mass of substanceT = change in temperature (Tf – Ti)Cp = specific heat of substance
33 Aim: How to determine the melting point of a substance? Challenge: To determine the melting point of water.Your write up should include the following components:I. TITLEII. PURPOSEMATERIALS-IV. PROCEDUREV. DATAVI. CALCULATIONS/GRAPHVII.CONCLUSION (including a discussion of sources of error.)
34 What is the freezing point of water? How would the mass of the sample affect the melting point? Explain.Describe the steps needed to determine the boiling point of water.Describe the phase changes that take place as water melts and as water boils.
35 Vocabulary condensation sublimation deposition temperature freezing vaporizationfusionsolidificationgaseous phasemeltheatsolid phaseheat of fusionliquid phaseheat of vaporizationkinetic molecular theory
36 October 17Objective: What are the characteristics of each state of matter?How to determine the amount of heat needed to change state?
37 Phases of MatterThe structure and arrangement of particles and their interactions determine the physical state of a substance at a given temperature and pressure.The three phases of matter (solids, liquids, and gases) have different properties.
41 Phase Change DURING A PHASE CHANGE TEMPERATURE REMAINS CONSTANT Phase changesMelting or Fusion: Phase change from solid to liquid. Endothermic.Vaporization – Phase change from liquid to gas. It occurs during boiling. Endothermic.
42 Phase ChangesEvaporation: from liquid to gas. It occurs at all temperatures and ONLY at the surface of the liquid. Endothermic.Condensation: From gas to liquid. Exothermic.Freezing, solidification or crystallization: from liquid to gas. Exothermic.
43 Special Phase ChangesSublimation: from solid directly to gas without changing to liquid first.Dry Ice CO2 (s) --> CO2 (g)Iodine I2 (s) --> I2 (g)
44 Special Phase ChangesDeposition: From gas to solid without going to liquid state.
46 HEAT OF FUSION FOR WATER (TABLE B) Amount of heat needed to completely melt 1g of water (ice!).334 J/g334 Joules of heat are necessary to completely melt 1 g of water.HOW MUCH HEAT IS NEEDED TO MELT 10 g OF WATER?
47 HEAT OF VAPORIZATION FOR WATER (TABLE T) The amount of heat needed to completely vaporize one g of water at its boiling point.2260 J/gWater needs 2260 J of heat per gram to convert to gas!
48 SummarizingWhen there is a change in temperature use Q = m x C x T While the substance is melting/freezing use Q = m x H f While the substance is boiling/condensing use Q = m x H vap
49 Do now!How much heat is needed to completely melt 10 g of ice at 0 0 C ?How much heat is needed to vaporize 10 g of water at C ?