IB Physics: Thermal Concepts

IB Physics: Thermal Concepts

1. State that temperature determines the direction of thermal energy transfer between two objects.

The temperature of an object usually measures how hot the object is. If two objects are placed in thermal contact, the temperature difference between the two objects will determine the direction of thermal energy transfer. Thermal energy is naturally transferred “down” the temperature difference—-from high to low temperatures.

After a period of time, the two objects are expected to reach roughly the same temperature.

We call this thermal equilibrium.

2. State the relation between the Kelvin and Celsius scales of temperature

Converting celsius into Kelvin

T(K) = T(°C) + 273

Temperature in Kelvin = Temperature in Celsius + 273

3. State that the internal energy of a substance is the total potential energy and random kinetic energy of the molecules of the substance

If the temperature of an object changes, then some sort of energy change must have taken place right?

The two possible forms of energy change are kinetic energy and potential energy.

Molecules have kinetic energy because they are moving. A molecule can have either Translational Kinetic Energy (the whole molecule is moving in a certain direction), or Rotational Kinetic Energy (the molecule is rotating about one or more axes).

Molecules have potential energy because of intermolecular forces. If we try to pull the molecules further apart, this would require more work against the inter molecular forces.

The Total energy a molecule possess is called “Internal Energy”. Heating a substance subsequently increases internal energy.

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4. Define the mole and molar mass

Mole: Another word for “amount of substance”.

Molar Mass: Mass of one mole of a substance is called the molar mass. If an element has a mass number of A, then the molar mass will simply be A grams.

5. Define the Avogadro constant

Definition:

“The number of atoms in 0.012 kg of Carbon-12, which happens to be 6.02 1023″