Structure 1.1-1.3
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What is an atom?
the smallest particle of an element that retains the properties of it
What are the two broad categories in which we classify substances?
pure substances and mixtures
What do elements and compounds have in common?
they are pure substances
What are pure substances vs mixtures?
pure - made up of one type of substance with a fixed composition mixtures - 2 or more substances combined, no fixed composition
What are elements?
building blocks of matter consisting of only one type of atom, cannot be broken down
What are ways in which elements can exist?
as individual atoms or atoms of the same element bonded together
What are allotropes?
different forms of an element in the same physical state
What are compounds?
pure substances composed of two or more different elements chemically combined in fixed ratios
Can compounds be separated using physical methods?
no because they are chemically bonded
What are physical methods of separation?
separation techniques based on the physical properties of the substance such as boiling point or solubility
What are mixtures?
combination of two or more elements or compounds no fixed ratios components retain individual properties
Can mixtures be separated using physical methods?
yes, they contain pure substances which are not chemically bonded
What are 2 classifications of mixtures?
homogenous- has a uniform composition with no visible phases/boundaries heterogenous- non-uniform composition with visible phases/boundaries
How is the distribution of components in hetero/homogenous mixtures?
homogenous - equally distributed and in the same state heterogenous - unequally distributed
What is filtration?
separation of an insoluble solid from a liquid/solution eg through a funnel
What is evaporation as a separation technique?
separating a mixture with a solute dissolved (usually in water)
What is solvation?
separation of a heterogeneous mixture of 2 solids based on differences in solubility
What is distillation?
separation of a liquid mixture based on difference in volatility/boiling points
What is chromatography?
used to separate components of a mixture paper - separate mixture of solutes in a solvent
What is the stationary and mobile phases in chromatography?
mobile - solvent undergoing separation stationary - paper used
How does chromatography work?
components of mixture move up paper at different rates due to different solubilities components with a greater affinity for mobile phase move further up
What is recrystallisation?
a separation technique to remove impurities within a solid uses varied solubilities of solids at different temperatures
Basic principles of recrystallisation?
impure mixture dissolved in hot solvent any insoluble impurities filtered off solution then cooled, solubility of solid decreases desired product forms crystals leaving soluble impurities in the solution, then filtered
What is the nature of collisions between particles?
elastic - no loss in k.e