Changing state

• The boiling point is the temperature at which a liquid turns into a gas
• The melting point is the temperature at which a solid turns into a liquid
• When a substance melts or boils, forces of attraction between its particles are overcome. In other words, some or all of the bonds between the particles break.
• Some bonds break going from solid to liquid. All the remaining bonds break by going from the liquid to gas state.
• The stronger the bonds and the more of them there are , the more energy must be transferred from the surroundings to break them.
• Substances have high melting point if they have many strong bonds in the solid state and high boiling points if they have many strong bonds in the liquid state.
• Bonds form when a substance condenses of freezes.
• Some bonds form from going from the gas to liquid state , but many bonds form from going to from the liquid to the solid state.
• Stored chemical energy is transferred to the surroundings usually by heating when chemical bonds form
• In metals there are metallic bonds which are strong.
• In ionic compounds there are ionic bonds which are strong.
• In giant covalent structures there are covalent bonds which are strong
• In simple molecules there are intermolecular forces which are weak.
• Metals, ionic compounds and giant covalent structures are usually solid at room temperature. However simple molecular substances are in the gas or liquid state of room temperature.
• Sublime means to change directly from solid to gas. Deposition is the opposite to this