Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
10 Cards in this Set
- Front
- Back
|
What is internal energy? |
The internal energy of a system is the sum of its internal kinetic energy & internal potential energy. |
|
|
What is internal kinetic energy? |
Internal kinetic energy is due to the motion of particles and depends on temperature |
|
|
What is internal potential energy? |
Internal potential energy is due to the intermolecular forces and depends on their separation |
|
|
What happens when a body is heated? |
When a body is heated, it either increases its internal kinetic energy (rise in temperature) or increases its internal potential energy (increase separation, change in state) |
|
|
What happens during melting? |
1) Particles are held by strong bonds in a solid and the internal potential energy of a solid is lower than that of a liquid 2) Thermal energy is absorbed and particles vibrate about fixed positions more vigorously 3) At melting point, thermal energy is absorbed to break the strong bonds between the particles, causing particles to move further apart from each other 4) The total internal potential energy increases while the total internal kinetic energy and temperature remains the same 5) The solid is now a liquid |
|
|
What happens during freezing? |
1) The intermolecular forces between liquid particles are weaker than those of a solid and the internal energy of a liquid is higher than that of a solid. 2) At freezing point, thermal energy is lost to the surroundings and strong bonds between particles are formed as the particles move closer together 3) The total internal potential energy decreases while the total internal kinetic energy and temperature remain constant 4) The liquid is now a solid where the particles are held in fixed positions by strong bonds |
|
|
What is evaporation? |
Evaporation is the process by which the more energetic molecules at the surface of the liquid overcome the downward attractive intermolecular forces from other water molecules and escape into the surroundings as gas molecules. |
|
|
Why does evaporation have a cooling effect? |
As the more energetic molecules escape, the average kinetic energy of the molecules decreases and the temperature decreases. |
|
|
Why does evaporation occur? |
1) Liquid molecules are in constant random motion and collide with each other continuously 2) When the molecules with higher kinetic energy collide with others when it is near the surface of the liquid, it may gain enough energy to overcome the intermolecular forces of the liquid and the atmospheric pressure and leave the liquid body |
|
|
What are the factors affecting evaporation? |
The rate of evaporation increases when:
1) temperature increases
- higher average kinetic energy of the molecules 2) surface area increases
- liquid molecules are more likely to leave the surface of the liquid 3) humidity decreases
– air is drier, lower likelihood of liquid molecules colliding and rebounding back into liquid 4) wind speed increases
- carries away liquid vapour formed by evaporation and lowers humidity 5) atmospheric pressure decreases
- less air molecules bombard liquid molecules, easier to escape 6) boiling point is low
– liquid is more volatile, easily changes from liquid to gas state |
