States of matter

• In solids, the particles are arranged closely together with strong forces between them. The particles vibrate around fixed positions but do not move far from these positions.
• In liquids, the particles are still close together but can slide past one another. This means they can flow or take on the shape of their container.
• The particles in liquids are also close together but can slide past one another. This means that they have more freedom to move than those in solids.
• The temperature at which a substance changes state is called its melting point (solid to liquid) or boiling point (liquid to gas).
• When a solid turns into a liquid, it absorbs energy because the bonds holding the atoms/molecules together have to be broken.
• Gases consist of particles which are widely spaced apart and moving very quickly. They collide frequently with other gas particles and with the walls of their container.
• Gases consist of particles which are very spread out and moving quickly. They have no fixed position so there is lots of space between the particles.
• When a liquid turns into a gas, it also absorbs energy as the inter-particle attractions break down.
• A change of state is when a substance changes its physical form without changing its chemical composition.
• When a substance changes state it absorbs or releases energy until its temperature remains constant (latent heat).
• A change of state occurs when there is an exchange of heat energy between a system and its surroundings.
• A change of state involves a transfer of heat energy from one object to another.
• A change from a liquid to a gas is called evaporation. It occurs when the kinetic energy of the molecules increases due to heating.
• Evaporation is the process by which a liquid turns into a gas.
• Increasing the pressure on a gas will cause it to compress and decrease in volume.
• Condensation is the reverse of evaporation - it's where water vapor turns back into liquid droplets.
• The amount of energy needed to convert one kilogram of water from ice at -10°C to steam at 100°C is called the latent heat of fusion.