Thermochemistry & Phases Test Phase Changes Energy transformations Conservation of Energy Endothermic/Exothermic reactions Temperature conversions (memorize K = ºC+ 273) Heat & Temperature Heat Flow Calorimetry problems Interpret potential energy diagrams Thermochemical Stoichiometry (Mole ↔ Energy) Properties of 3 Phases Names of Phase Changes Endothermic/Exothermic Phases Changes Energy Changes During Phase Changes Heat of Fusion/Vaporization Calculations Dynamic Equilibrium During Phase Changes Vapor Pressure Boiling (Changes Using Elevation or Pressure) Interpreting Heating Curves

Jeopardy Thermo 1 Thermo 2 Phase 1 Phase 2 100 200 300 400 500

Credits That’s all folks. Exit

The burning of magnesium involves the conversion of A.) heat energy to light energy B.) light energy to heat energy C.) light energy to chemical energy D.) chemical energy to light energy

D Chemical Energy to Light Energy Energy is conserved (not created or destroyed) in all chemical reactions. Therefore the light energy that is emitted in this reaction must have come from the chemical energy stored in the bonds for magnesium and oxygen

NaOH(s) + H2O(l)  NaOH(aq) + heat What change occurs when pellets of NaOH are added to water and stirred? NaOH(s) + H2O(l)  NaOH(aq) + heat A.) The water temperature increases as chemical energy is converted to heat energy. B.) The water temperature increases as heat energy is stored as chemical energy. C.) The water temperature decreases as chemical energy is converted to heat energy. D.) The water temperature decreases as heat energy is stored as chemical energy.

A. The water temperature increases as chemical energy is converted to heat energy. Heat is a product. This means that the reaction is exothermic and that energy is released, causing the temperature of the water to increase as it absorbs this heat energy. The heat energy is transformed from the chemical energy stored in the substances bonds.

The average kinetic energy of water molecules is greatest in which of these samples? A.) 10 g of water at 35°C B.) 10 g of water at 55°C C.) 100 g of water at 25°C D.) 100 g of water at 45°C

B. 10 g of water at 55°C Temperature is the measure of a samples average kinetic energy. The sample with the highest temperature must also have the highest kinetic energy. Kinetic energy and temperature do not rely on the amount of sample (mass).

Solid X is placed in contact with solid Y Solid X is placed in contact with solid Y. Heat will flow spontaneously from X to Y when A.) X is 20oC and Y is 20oC B.) X is 10oC and Y is 5oC C.) X is -25oC and Y is -10oC D.) X is 25oC and Y is 30oC

B. X is 10oC and Y is 5oC Heat energy naturally flows from hot to cold (high temperature to low temperature.

Which Celcius temperature is equivalent to 300 K? A.) 0 ºC B.) 27 ºC C.) 300 ºC D.) 573 ºC

B. 27 ºC K = C + 273 *You Must Memorize This Formula* 300 K = °C + 273 -273 -273 °C = 27

The specific heat of silver is 0. 24 J/gºC The specific heat of silver is 0.24 J/gºC. How much heat is needed to warm 4.37 g of silver from 25.0ºC to 27.5ºC? A.) 2.62 J B.) 0.14 J C.) 45.5 J D.) 0.022 J

A. 2.62 J Q = mcΔT Q = (4.37 g)(0.24 J/g°C)(27.5 °C – 25.0 °C) Q = 2.62 J This reaction is endothermic because q is positive

How much energy is released when 36 How much energy is released when 36.0 grams of steam condenses into liquid water? A.) 22.0 kJ B.) 81.4 kJ C.) 195 kJ D.) 1580 kJ

B 81.4 kJ Condensing is the opposite of vaporization Q = mHv Q = (36.0 g)(2260 J/g) Q = 81,360 J

What amount of heat is required to completely melt a 29 What amount of heat is required to completely melt a 29.95 gram sample of H2O(s) at 0ºC? A.) 334 J B.) 2260 J C.) 1.00 × 103 J D.) 1.00 × 104 J

D 1.00 × 104 J Melting is also known as fusion Q = mHf Q = (29.95 g)(334 J/g) Q = 10,003 J

Which arrow represents the potential energy of the reactants? Given the potential energy diagram of a chemical reaction: . . . (see image) Which arrow represents the potential energy of the reactants? A.) B.) C.) D.)

B A = Activation Energy B = Reactants C = Activated Complex D = Products

In a potential energy diagram, the difference between the potential energy of the products and the potential energy of the reactants is equal to the A.) heat of reaction B.) entropy of the reaction C.) activation energy of the forward reaction D.) activation energy of the reverse reaction

A heat of reaction ΔH = Hproducts – Hreactants

Calculate the energy required to produce 7 moles of Cl2O7 2 Cl2 + 7 O2 + 543.4 kJ  2 Cl2O7 Calculate the energy required to produce 7 moles of Cl2O7 A.) 29.26 kJ B.) 271.7 kJ C.) 543.4 kJ D.) 1901.9 kJ

D 1901.9 kJ 2 Cl2 + 7 O2 + 543.4 kJ  2 Cl2O7 7 = X 2 543.4

Two basic properties of the gas phase are A.) a definite shape and a definite volume B.) a definite shape but no definite volume C.) no definite shape but a definite volume D.) no definite shape and no definite volume

D no definite shape and no definite volume Solid = definite shape and definite volume Liquid = definite volume but no definite shape

Which phase change is an exothermic process? A.) CO2(s)  CO2(g) B.) NH3(g)  NH3(l) C.) Cu(s)  Cu(l) D.) Hg(l)  Hg(g)

G L S B NH3(g)  NH3(l) EXOTHERMIC ENDOTHERMIC RELEASES ENERGY NEEDS ENERGY S

A pot of water is brought to a boil A pot of water is brought to a boil. The temperature of the water when it started to boil was 100.0ºC. What do you expect the thermometer to read after boiling for 15 minutes? A.) Below 100.0ºC B.) 100.0ºC C.) 105.0ºC D.) 115.0ºC E.) Above 115.0ºC

B 100.0ºC Temperature does not change during a phase change. The heat energy is being converted into potential energy during this phase change, not kinetic energy that would result in a change in temperature.

The graph (see image) represents the uniform heating of a substance, starting with the substance as a solid below its melting point. Which line segment represents an increase in potential energy and no change in average kinetic energy? A) 1 B) 2 C) 3 D) 4 D.) 4 B.) 2 A.) 1 C.) 3

B BC Kinetic energy is seen by a change in temperature such as AB, CD, and EF. Potential energy changes on the plateaus, where the temperature does not change, such as BC and DE

The graph represents the uniform cooling of a substance, starting with the substance as a gas above its boiling point. During which interval is the substance completely in the liquid phase? A.) AB B.) BC C.) CD D.) DE

C CD AB = Gas BC = Condensation (gas and liquid) CD = Liquid DE = Melting (liquid and solid) EF = solid

As the temperature of a liquid increases, its vapor pressure A.) decreases B.) increases C.) remains the same

B increases As the temperature increases so does the kinetic energy of the particles. An increase in the pressure pushing up is caused.

As the pressure on the surface of a liquid decreases (atmospheric pressure), the temperature at which the liquid will boil A.) decreases B.) increases C.) remains the same

A decreases Substances boil when the vapor pressure (up) is equal to the atmospheric pressure (down). If the pressure pushing down is lessened then less pressure up is needed to reach the boiling point. This means that a lower temperature is needed to get the necessary vapor pressure.

At which temperature will equilibrium exist for the system below? H2O(s) ↔ H2O(l) A.) 0 K B.) 100 K C.) 273 K D.) 373 K

C 273 K Solid and liquid exist at the melting/freezing point, 0 °C for water. K = °C + 273 K = 0 °C+ 273 K = 273

Category 4 $500 Answer

Category 4 $500 Question?