Internal Energy
What is internal energy?
Internal energy of a system is defined as the sum of the random distribution of kinetic and potential energies of its molecules
What is a thermometer?
A device used to measure temperature
What is specific heat capacity?
It is the energy required to heat 1Kg of mass by 1 degree Celsius
What does the first law of thermodynamic state?
The first law of thermodynamics states that energy cannot be created or destroyed, but can change from one form to another
What are the 2 ways to increase the internal energy?
Heat it so that the molecules vibrate vigorously and gain kinetic energy. The increase in kinetic energy shows that the temperature is also increasing
Compress the object so that the molecules bounce off the wall and gain kinetic energy, therefore increasing the temperature
Why is water not a suitable liquid to replace mercury in a thermometer?
The the expansion of water is non linear.
State the formula for specific heat capacity and specific latent heat and define each variable.
Specific heat capacity
E = mc Δ θ
Specific latent heat
E = mL
What is the definition of thermal equilibrium?
No NET thermal energy transferred between 2 objects
Define the equation for internal energy stating each variable
Increase in internal energy = energy supplied by heat + work done on the system
Why was the Kelvin scale invented?
scientists used this scale to show that 0 K represents complete absence of thermal energy
What is the two types of specific latent heat and describe each of them.
Specific latent heat of fusion is the energy needed per unit mass to convert the unit mass of solid to liquid without change in temperature
Specific latent heat of vaporization is the energy needed per unit mass to convert unit mass of liquid to gas without change in temperature
State what is absolute zero
The temperature at which the atoms and molecules in all substances have zero kinetic and potential energy
What is isothermal change?
insulating the system to prevent heat from entering or escaping, or by pushing the piston so slowly that there is no temperature change
What are the 3 physical properties that a thermometer uses to measure temperature?
A liquid-in-glass thermometer depends on the density change of a liquid (commonly mercury)
It consists of a thin glass capillary tube containing a liquid that expands with temperature
A scale along the side of the tube allows the temperature to be measured based on the length of liquid within the tube
The mass of nitrogen gas in another container is 24.0g at a temperature of 27°C. The gas is cooled to its boiling point of –196°C. Assume all the gas condenses to a liquid. For this change, the specific heat capacity of nitrogen gas is 1.04 kJ kg–1K–1. The specific latent heat of vaporization of nitrogen is 199kJkg–1. Determine the thermal energy, in kJ, removed from the nitrogen gas.
energy = .................................................... kJ
10.3 Kj
What is a thermocouple and what does it consist of?
A thermocouple is a device that consists of wires made of two different metals across which an e.m.f is produced when the two junctions of the wires are at different temperatures
The atoms of an ideal gas occupy a container of volume 2.30 × 10–3m3 at pressure
2.60 × 105Pa and temperature 180K
The gas is heated at constant pressure so that its
volume becomes 3.80 × 10–3m3 at a temperature T (297 K). The thermal energy supplied to the gas is 980J. Find the work done on the gas in J.
-390J
What is the approximate temperature in space? (K)
2.7 K
The thermometer is initially at 23.0°C, as shown in Fig. 2.1. It is used to measure the temperature of an insulated beaker of water that is at 37.4°C. The bulb of the thermometer is inserted into the water, and the water is stirred until the reading on the thermometer becomes steady. The mass of water in the beaker is 18.7g. The mass of mercury in the thermometer is 6.94g. The specific heat capacity of water is 4.18J g–1K–1. The specific heat capacity of mercury is 0.140Jg–1K–1. The glass of the thermometer and the beaker containing the water can be considered to have negligible heat capacity.
Calculate, to three significant figures, the final steady temperature indicated by the thermometer in the water.
temperature = .................................................... °C
T = 37.2 °C
On what property is the Kelvin scale (thermodynamic scale) defined in terms of?
Trick question: not defined in terms of a property of any particular substance