Exam 17: Phases and Phase Changes

A 771.0-kg copper bar is put into a smelter for melting.The initial temperature of the copper is 300.0 K.How much heat must the smelter produce to completely melt the copper bar? The specific heat for copper is 386 J/kg ∙ K,the heat of fusion for copper is 205,000 J/kg,and its melting point is 1357 K.

A 50-kg air conditioner is placed on top of a concrete pad that is 20 cm thick and has a cross-sectional area of 3.0 m².What is the change in thickness of the pad caused by the air conditioner? Young's modulus for concrete is 2.3 × 10¹⁰ N/m².

In an experiment to measure the thermal conductivity of a certain material,a slab of material 10.0 mm thick separates a steam chamber from a block of ice with a square cross-section with dimensions 8.00 cm × 8.00 cm.After 5.00 min of running the experiment,64.0 g of ice have melted.What is the thermal conductivity of this material? The latent heat of fusion of water is 33.5 × 10⁴ J/kg,the latent heat of vaporization of water is 2.256 × 10⁶ J/kg,and both the ice and water are under 1.00 atm of pressure.

Which of the following are SI units of Young's modulus? (There could be more than one correct choice. )

A 25-kg piece of equipment can be hung by steel wires of length 1.00 m,2.00 m,or 3.00 m.If all the wires have the same diameter,which one will stretch the greatest percent?

Your lungs hold 4.2 L of air at a temperature of 27°C and a pressure of 101.3 kPa.How many moles of air do your lungs hold? (R = 8.31 J/mol ∙ K)

An ideal gas occupies 6.00 × 10² cm³ at 20°C.At what temperature will it occupy 1.20 × 10³ cm³ if the pressure is held constant?

A sealed container holds 0.020 moles of ideal nitrogen (N₂)gas,at a pressure of 1.5 atm and a temperature of 290 K.The atomic mass of nitrogen is 14.0 g/mol.What is the average translational kinetic energy of a nitrogen molecule? The Boltzmann constant is 1.38 × 10^-23 J/K.

A 400-g block of iron at 400°C is dropped into a calorimeter (of negligible heat capacity)containing 60 g of water at 30°C.How much steam is produced? The latent heat of vaporization of water is 22.6 × 10⁵ J/kg and its specific heat capacity is 4186 J/kg ∙ K.The average specific heat of iron over this temperature range is 560 J/kg ∙ K.

What is the average translational kinetic energy of an ideal gas at The Boltzmann constant is 1.38 × 10^-23 J/K.

A vertical 30-cm steel rod,1.0 cm in diameter,supports a 300-kg mass.What is the change in length of the rod caused by this mass? Young's modulus for steel is 2.0 × 10¹¹ N/m².

A substance has a melting point of 20°C and a heat of fusion of 3.4 × J/kg.The boiling point is And the heat of vaporization is At a pressure of one atmosphere.The specific heats for the solid,liquid,and gaseous phases are 600 J/kg ∙ K (solid),1000 J/kg ∙ K (liquid),and 400 J/kg ∙ K (gaseous).How much heat is required to raise the temperature of Of this substance from To At a pressure of one atmosphere?

A steel wire,3.2 m long,has a diameter of 1.2 mm.The wire stretches 1.6 mm when it bears a load.Young's modulus for steel is 2.0 × 10¹¹ Pa.The mass of the load is closest to

An 920-g piece of iron at 100°C is dropped into a calorimeter of negligible heat capacity containing 50 g of ice at 0°C and 92 g of water,also at 0°C.What is the final temperature of the system? The specific heat of iron is 448 J/kg ∙ K,that of water is 4186 J/kg ∙ K,and the latent heat of fusion of water is 33.5 × 10⁴ J/kg.

A 25-kg piece of equipment can be hung by steel wires of length 1.00 m,2.00 m,or 3.00 m.If all the wires have the same diameter,which one will stretch the greatest distance?

A 1200-kg car is being raised with a constant acceleration of 2.53 m/s² by a crane,using a 20-m long steel cable that is 1.5 cm in diameter.Young's modulus for steel is 2.0 × 10¹¹ N/m².What is the change in length of the cable caused by lifting the car?

If the temperature of a gas is increased from 20°C to 100°C,by what factor does the rms speed of an ideal molecule change?

A large 75-kg lighting fixture can be hung from wires of identical size and shape made of aluminum,brass,or copper.The values of Young's modulus for these metals are 0.70 × 10¹¹ Pa (aluminum),0.91 × 10¹¹ (brass),and 1.1 × 10¹¹ (copper).Which wire would stretch the least distance?

A certain automobile tire has a volume of 0.0185 m³.If the absolute (or total)pressure in the tire is 500 kPa and the temperature is 298 K,how many molecules are there inside the tire? (R = 8.31 J/mol ∙ K,N_A = 6.022 × 10²³ molecules/mol)

Two wires are made out of the same metal,but one wire is twice as long as the other wire.Which wire will have the greatest elastic modulus?