Thermodynamics – CramNow

Category: Thermodynamics

Internal Energy and Temperature

1 / 10

In the kinetic energy equation, what does m represent?

The average mass of individual molecules

It is a constant

The overall mass of the system

2 / 10

What unit is used to measure energy?

Watt

Joule

Calorie

3 / 10

Select the correct statement

The greater the temperature, the lower the average kinetic energy.

The greater the temperature, the greater the average kinetic energy.

The temperature has no effect on the average kinetic energy.

4 / 10

Select the correct statement

Total internal energy is the sum of the kinetic and potential energy of the molecules within a system.

Total internal energy is the sum of the potential energy of the molecules within a system.

Total internal energy is the sum of the kinetic energy of the molecules within a system.

5 / 10

Select the correct statement

The further apart molecules are in a system, the greater their potential energies.

The further apart molecules are in a system, the lower their potential energies.

The further apart molecules are in a system has no effect on their potential energy.

6 / 10

Absolute Zero is the lowest possible temperature and is equal to:

0 K

0 °F

0 °C

7 / 10

A temperature of 0°C is equivalent to...

0 K

−273.15 K

273.15 K

8 / 10

The temperature in sunny Sheffield is 25°C and it is 400.15 K on the sunny surface of the moon. What is the difference in temperature in Kelvin?

152 K

375.15 K

378.15 K

9 / 10

The perfect temperature to brew a cup of tea is said to be 355.15 K, what is this in Celsius?

80 °C

81 °C

82 °C

10 / 10

What is not a reason why scientists use the Kelvin scale?

Scientist wanted a temperature scale where zero reflects the complete absence of thermal energy.

Scientists wanted a temperature scale that wasn't directly related to volume.

Scientists wanted a temperature scale with a finite zero point.

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Thermal Properties of Materials

1 / 10

What is the definition of specific heat capacity?

The amount of energy required to raise the temperature of 1 g of a substance by 1 K.

The amount of energy lost when 1 g of a substance has a reduction in temperature of 1 K.

The amount of energy required to raise the temperature of 1 kg of a substance by 1 K.

2 / 10

A 2.8 kg sample of an unknown metal takes 210 kJ of energy to increase its temperature by 26.7 K. Calculate the specific heat capacity of the unknown metal sample.

2.8 J kg^-1K^-1

2809 J kg^-1K^-1

1.570x10⁴ J kg^-1K^-1

1.570x10⁷ J kg^-1K^-1

3 / 10

Select the correct statement

The greater the mass of a substance, the more energy required to increase its overall temperature by 1 K.

The greater the specific heat capacity of a substance, the more energy required to increase its overall temperature by 1 K.

The greater the temperature change of a substance, the greater the energy gained by it.

All of these statements are correct.

4 / 10

Which diagram best represents water molecules at 353.15 K?

5 / 10

What is happening at point X on this diagram?

The nitrogen molecules are gaining kinetic energy as the overall temperature of the substance increases.

The nitrogen molecules are gaining potential energy as the overall temperature of the substance increases.

The nitrogen molecules are not gaining kinetic energy, but as their bonds are being broken their potential energy is increasing.

The nitrogen molecules are not gaining kinetic energy, but are becoming hotter as individual molecules increasing their potential energy.

6 / 10

What is happening at point Y on this diagram?

The nitrogen molecules are gaining kinetic energy as the overall temperature of the substance increases.

The nitrogen molecules are gaining potential energy as the overall temperature of the substance increases.

The nitrogen molecules are not gaining kinetic energy, but as their bonds are being broken their potential energy is increasing.

The nitrogen molecules are not gaining kinetic energy, but are becoming hotter as individual molecules increasing their potential energy.

7 / 10

Which statement best describes the specific latent heat of fusion?

The energy required to melt 1 kg of a solid.

The energy required to evaporate 1 kg of a liquid.

The energy required to freeze 1kg of a liquid.

The energy required to condense 1kg of a gas.

8 / 10

Which statement best describes the specific latent heat of vaporisation?

The energy required to melt 1 kg of a solid.

The energy required to evaporate 1 kg of a liquid.

The energy required to freeze 1kg of a liquid.

The energy required to condense 1kg of a gas.

9 / 10

A 0.3 kg metal ring is heated to 130 °C then dropped into 1700 g of water with a temperature of 304 K (c_w = 4180 J kg^-1 K ^-1). Eventually, the ring and water reach a thermal equilibrium of 23 °C. Calculate an estimate for the specific heat capacity of the metal the ring is made from.

1.43x10³ J kg^-1 K ^-1

1.59x10³ J kg^-1 K ^-1

1.86x10³ J kg^-1 K ^-1

6.24x10³ J kg^-1 K ^-1

10 / 10

The 1.80 kW kettle in the prep room is filled with 1.30 L of water and switched on at the start of a 15 minute break and takes two minutes for the water to reach boiling point. Unfortunately, there is an issue and the kettle fails to switch off. At the end of break, a technician walks in after completing their equipment changeovers and manually turns the kettle off, then makes themselves a cup of tea using 330 ml of the boiling water. Assuming no heat loss, how much water remains in the kettle? [L_v = 2.26x10⁶ J kg^-1, density of water at 100°C = 958 kg m^-3]

0.318 L

0.358 L

0.625 L

0.717 L

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Ideal Gases

1 / 10

What is an ideal gas?

Gases from Group 0 of the periodic table

A gas that in which all collisions between atoms or molecules are inelastic.

A theoretical gas that obeys the gas laws (and the equation of state for an ideal gas).

2 / 10

For a fixed mass of gas, which graph shown best represents Charles's Law?

3 / 10

For a fixed mass of gas, which graph shown best represents Boyle's Law?

4 / 10

For a fixed mass of gas, which graph shown best represents The Pressure Law?

5 / 10

The best vacuum that a physics teacher dreams of obtaining in their classroom is laboratory standard. This is about 1 x 10^-13 Pa. How many molecules per m³ at 25 °C?

2.43x10⁷ molecules

2.90x10⁷ molecules

2.43x10⁸ molecules

2.90x10⁷ molecules

6 / 10

A storage tank can store 30 L of compressed helium and a pressure of 30 atm at 20 °C. The tank is current 56% full. How many 12 cm radius balloons filled to 1.2 atm will the tank fill? 1 atm = 101.325 kPa. Assume the balloons are perfectly spherical

42 balloons

58 balloons

67 balloons

73 balloons

7 / 10

You lock up your bike in the school racks before registration and your bicycle tyres are fully inflated and leak free, with an absolute pressure of 7.00 × 10⁵ Pa each at 14 °C. You go back at lunchtime, and notice the sun has been shining on your front tyre all morning and the temperature is now 27 °C. What is the pressure in the front tyre?

3.62x10⁵ Pa

6.70x10⁵ Pa

7.32x10⁵ Pa

1.35x10⁷ Pa

8 / 10

You're at Cleethorpes for your birthday and your friends have bought you a large helium-filled balloon, which you accidently let go of in the excitement of it all. What is the pressure inside your balloon if it starts out at sea level (1 atm) at a British summer seaside temperature of 10 ºC and rises to an altitude where its volume is twenty times the original volume and its temperature is –50 °C? 1 atm = 101.325 kPa.

0.250 Pa

5.000 Pa

3.993 kPa

79.854 kPa

9 / 10

On average, the lungs of an average person holds 2 L of air. Calculate the number of molecules in the lungs, assuming the temperature is 37 °C and the pressure 101.325 kPa.

4.73x10²² molecules

3.97x10²³ molecules

4.73x10²⁵ molecules

3.97x10²⁶ molecules

10 / 10

A fire extinguisher works by pressurised air forcing the water out. A water fire extinguisher contains 4 L of air at 1345 kPa at 23 °C. When discharged, the volume of air increases to 7.5 L and the temperature decreases to 2.5 °C. Calculate final pressure.

538 Pa

663 Pa

538 kPa

663 kPa

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Kinetic Theory and Internal Energy

1 / 10

The kinetic theory of gases gives the equation shown above. Which of the following statements is not an assumption made in the derivation of this equation.

No intermolecular attractions

Perfectly elastic collisions

Gas molecules are in random motion

Time between impacts are very short in comparison to impact time

2 / 10

What would cause an increase of the internal energy of an ideal gas?

Increase of absolute temperature

Decrease of absolute temperature

Increase of volume

Decrease of volume

3 / 10

Internal energy is...

The total kinetic energy of all molecules in a system.

The total kinetic and potential energy of all molecules in a system.

The total kinetic and potential energy of all particles in a system.

The total kinetic energy of all atoms in a system.

4 / 10

The molecules in a sample of gas have a mass of 4.30x10^-23 kg. Calculate the r.m.s. speed of the gas molecules when they are at a temperature of 30 °C.

5.37 ms^-1

17.08 ms^-1

28.88 ms^-1

291.87 ms^-1

5 / 10

The molecules in a sample of gas are moving at r.m.s. speed of 500 ms^-1 at a temperature of 21 °C. Calculate the mass of the gas molecules.

3.78x10^-27 kg

4.87x10^-26 kg

1.74x10^-24 kg

2.44x10^-23 kg

6 / 10

In Switzerland, CERN has 60 gas tanks that can hold 250 m³ of helium gas at 0 °C and 101.325 kPa. The r.m.s. speed of the helium is 1.25 kms^-1. Calculate the total number of helium molecules if half of the tanks are full.

6.72x10²⁷

2.02x10²⁹

4.03x10²⁹

2.28x10⁵¹

7 / 10

The r.m.s. speed of nitrogen molecules at 98 °C is 455 ms^-1. Calculate the r.m.s. speed at 1321 °C.

31 ms^-1

942.98 ms^-1

977.15 ms^-1

1181.23 ms^-1

8 / 10

Calculate the temperature at which the r.m.s. speed of oxygen molecules is half their r.m.s. speed at 56.0 °C.

-190.9 °C

-35.2 °C

14.0 °C

28.0 °C

9 / 10

When a gas particle (atom or molecule) directly collides with the wall of it's container, what is it's change in momentum?

-mu

2mu

-2mu

10 / 10

The density of air at 20 °C is 1.275 kgm^-3 and the atmospheric pressure is 101.325 kPa. Calculate the r.m.s. speed of the air molecules.

303.324 ms^-1

385.405 ms^-1

440.226 ms^-1

488.274 ms^-1

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Black Body Radiators

1 / 10

Complete the sentence: "A black body radiator is..."

A perfect absorber

A perfect emitter

A perfect absorber and emitter

2 / 10

Which wavelengths of electromagnetic radiation can a black body radiator absorb?

IR to UV

Radiowaves to Gamma Rays

Visible light only

X-Rays and Gamma Rays

3 / 10

Which wavelengths of electromagnetic radiation can a black body radiator emit?

IR to UV

Radiowaves to Gamma Rays

Visible light only

X-Rays and Gamma Rays

4 / 10

What happens to the temperature of a body that absorbs IR faster than it emits?

Temperature decreases

Temperature increases

Temperature stays the same

5 / 10

Calculate the temperature of a black body radiator that has a peak wavelength of 106 nm.

2.7x10^-5 K

3.7x10^-5 K

2.7x10³ K

3.7x10³ K

6 / 10

Calculate the frequency of a black body radiator that has a temperature of 4.2x10⁴ K.

4.35x10^-3 Hz

20.7 Hz

1.4x10⁷ Hz

6.9x10⁸ Hz

7 / 10

Calculate λ_max for a black body radiator at a temperature of 2300 K.

1.26x10^-3 m

2.898x10^-3 m

6.67 m

7.93x10⁵ m

8 / 10

On the diagram shown, select the curve that represents the black body with the highest temperature.

All are same temperature.

9 / 10

Blinkend Bladus is a completely made up star. However, it has a surface area of 1.45x10¹⁷ m² and produces a black body spectrum with peak wavelength of 280 nm. Calculate the luminosity of Blinkend Bladus.

2.30x10^-7 W

0.01 W

8.51x10¹³ W

3.59x10¹⁹ W

10 / 10

Regulus is the brightest star in the Leo constellation. It has a surface temperature of 12460 K and a luminosity of 288 L_☉. Calculate its radius. 1 L_☉ (solar luminosity) = 3.828×10²⁶ W

2.15x10⁹ m

2.53x10⁹ m

2.53x10¹⁰ m

1.24x10³¹ m

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