Elements, compounds and mixtures Flashcards
What is relative atomic mass
The mass of an atom compared to the mass of a Carbon 12 atom / 12
What does chemical formula tell you
How much atoms of each elements there are in a unit of substance eg H2O
What is relative formula mass
Total relative atomic mass of a chemical formula
What is an empirical formula
The simplest whole number ratio of the atoms of each element in a compound
Define purity
A substance consisting of just one element or compound
How can you determine melting point and from that purity
Heat a substance slowly and stir, then compare this to that of a pure substance
How does filtration work
Separates an insoluble solid form a liquid substance as the solid molecules are unable to pass through the filter paper
How does crystallisation work
Saturate the solution and slowly evaporate it until crystals form
Describe simple distillation
Separates solvent from solution, involves boiling the solvent which is then condensed by a condenser. This relies on the solvent having a much lower boiling point than the solute
How does fractional distillation vary from simple distillation
Separates 2 or more substances from a mixture in the liquid state, using a fractional column
How does chromatography work
Relies on a stationary and mobile phase
Explain thin layer chromatography
-Put the solvent in a chromatography tank
-Add a small amount of sample to the base line of the silica or ammonia coated plate
-Let the solvent travel through and remove plate before it reaches the top
-Analyse the pattern
How does gas chromatography work
The sample is turned into the gas state when injected. The carrier gas pushes the sample through, each component taking different times to travel and leave the column which the detector sends to the chromatogram.
What are the chemical properties of metals and non metals
metals make positive ions, non-metal negative
Metals dont react with eachother, non-metals make compounds
Metal oxides are alkaline non-metal acidic
What is a polymer
A molecule made of many smaller molecules called monomers
What are monomers
simple molecules made from covalently bonded non metals
What are metallic bonds like
Positively charged metal ions are attracted to delocalised electrons
What did Mendeleev do
Mendeleev’s table included atomic weights of known elements, knowledge of their chemical reactions and their physical properties.Mendeleev also predicted elements.
What are the patterns of chemical properties in the periodic table
-Elements arranged in order of increasing atomic number
-The electronic structure determines chemical properties
What is diamond like
Exists as a giant covalent structure
Each carbon bonded to 4 others
High melting point hard and insulator
What is graphite like
Giant covalent structure
Each carbon bonded to 3 others
Conductor
High melting point
Slippery
What is graphene like
A single layer of graphene
Slippery
Extremely strong
Conductor
What are fullerenes like
Eg nanotubes or bucky balls
Used as lubricants ect
What happens when a substance changes state
Some or all bonds between particles break when melting or boiling, bonds form when condensing or freezing
