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Description
Flashcards by Farha Idrees, updated more than 1 year ago
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Created by Farha Idrees
over 6 years ago
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| Question | Answer |
| _______ is needed to melt a solid or boil a liquid. | ENERGY |
| For any pure substance undergoing a change of state- | -its temperature stays the same whilst the change of state takes place. |
| What changes happen at the: a) melting point b) boiling point | a) melting + freezing b) boiling + condensation |
| What can affect the melting/boiling points of a liquid? Give an example. | any impurities in a substance e.g. the melting point of water is lowered if you add salt to the water |
| Describe what happens during the horizontal sections of the graph. | during this time, the extra heat added does not go to increasing the temperature, but rather to overcome the force of attraction between the particles, hence the reason why the temperature stays the same |
| What is the difference between evaporation and boiling? | evaporation: happens at any temperature and at the surface of the liquid boiling: at the boiling point, when bubbles of vapour form inside the liquid + rise to the surface to release the gas |
| What can energy added do? | 1. increase kinetic energy 2. break/ make bonds (NEVER BOTH at the same time) |
| potential energy = | = intermolecular forces |
| What is latent heat? | the energy needed for a substance to change its state (and break its bonds) without changing the temperature |
| Describe specific latent heat | the amount of energy required to melt or boil 1kg of a substance without changing its temperature |
| Give the formula for specific latent heat. | latent heat = energy / mass |
| What does the amount of energy required to change the state of a sample depend on? | 1. the substance 2. the state change 3. the mass |
| define specific latent heat of fusion | the energy needed to change the state of 1kg of a substance from solid to liquid |
| define specific latent heat of vaporisation | energy needed to change the state of 1kg of a substance from liquid to gas |
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