Chemistry notes
Chapter 1 : The Particulate Nature Of Matter
Matter is divided into 3 states. They are sold, liquid and gas. Matter is all the substances and materials from which the physical universe is composed.
Solids have a definite shape and volume. This may change if affected by temperature. Solids usually expand upon heating and contract upon cooling.
A liquid at a given temp. has a defiant volume and takes the shape of the container it is placed in. Its volume is affected by changes in temp.
A gas at a defined temp. has no definite volume or shape. It takes both the shape and volume of its container.
Liquids and gases are compressible unlike solids. Liquids are less compressive than gases.
The kinetic theory
It states that all matter is made up of particles
The three main points of this theory are:
- All matter is made up tiny, moving particles, invisible to the naked eye. Different substances have different types of particles(atoms, molecules and ions)which have different sizes.
- The particles move all the time.the higher the temp. , the faster they move on an average.
- Heavier particles move more slowly than lighter ones on an average
The particles
- Solids
- The particles attract each other. There are attractive forces between the particles of a solid which hold them close together. They have limited movement and vibrate about fixed position. They are arranged in a regular patten.
- Liquids
- In a liquid the particles are still close together but further away than the particles of a solid.. they move in a random way and often collide with each other. They have weaker forces than that of a solid. They have more energy than solids on an average.
- Gases
- The particles are relatively far apart. They are free to move anywhere around their container. They move randomly with great speed and collide with each other and with the walls of their container.
Changes of state
Solid to liquid ———> Melting Liquid to solid ————> Freezing
Liquid to gas ———> Boiling Gas to Liquid —————> Condensation
Gas to solid ————> Sublimation Solid to gas —————> Sublimation
Diffusion:
The random movement of particles from their region of higher concentration to their region of lower concentration down the concentration gradient.
when diffusion takes place between a liquid and gas it is called intimate mixing.
Brownian Motion:
The random motion of visible particles caused by much smaller, invisible particles is called Brownian motion.
prepIGCSE 