NATURE OF MATTER Flashcards
Define ELEMENTS
A chemical substance that cannot be broken down into a smaller substance by chemical means
Pure substance in which each atom has the same number of protons in the nucleus
Define COMPOUNDS
A pure substance formed when 2 or more elements are combined chemically in a fixed ratio
Elements in a compound are chemically combined –> can only be converted into their elements again by chemical reactions
Define MIXTURE
2 or more substances mixed together, not chemically bonded together
They retain their individual properties since they are not chemically bonded, and can be separated from each other by physical means
Components of a mixture can be mixed together in any proportion
Chemical properties
How a substance behaves in a chemical reaction
Physical properties
All other properties of a substance
eg. melting point, density, hardness, electrical conductivity
Define HOMOGENOUS MIXTURE
Uniform composition throughout the mixture
Consists of only one phase
Different components can be separated by chemical means
eg. mouthwash, rainwater
Define HETEROGENOUS MIXTURE
Does not have uniform composition
Consists of separate phases
Different components can be separated by chemical means
eg. oil and water
Comparing HETEROGENOUS and HOMOGENEOUS mixtures
They contain 2 or more elements or compounds mixed together and can be separated by physical means
Contrasting HETEROGENOUS and HOMOGENEOUS mixtures
HOMOGENOUS:
Uniform composition
Uniform properties
HETEROGENOUS:
Non-unifrom composition
Non-uniform properties
Liquid to Gas?
Boiling
Gas to Liquid?
Condensation
Refers to the change in physical state from gas to liquid
Solid to Liquid?
Melting
Liquid to Solid?
Freezing
Gas to Solid?
Deposition
Refers to the change in physical state from gas to solid
Solid to Gas?
Sublimation
eg. Dry ice (CO2 in solid state), Iodine,
Ammonium chloride
Describe a solid
A solid’s particles are packed closely together. Due to relatively strong forces of attraction between them, particles are unable to move freely and can only vibrate about mean positions. As a result, a solid has a stable, definite shape and a definite volume. (Solids can only change shape under force, as when broken or cut.)
Describe a liquid
The particles have weaker forces between them, and so are able to move around each other. As the forces between the particles are weaker than those in solids, liquids are able to flow and take the shape of the container they are in.
Describe a gas
Gas is a form of matter with molecules that have weak forces of attraction between them. The particles move freely and quickly, filling the shape and volume of their container. Unlike solids and liquids, gases are easily compressed due to their weak intermolecular forces.
Temperature definition?
Temperature is a measure of the average kinetic energy of the particles in a substance.
[The temperature, T, in Kelvin (K) is a measure of average kinetic energy Ek of particles]
Kelvin is the SI unit of temperature
Temperature conversion
Temp (K) = Temp (C) + 273.15
