Flashcards in Properties and Structure of Materials Deck (127):
Substances that contain particles in the size range of 1-100 nm.
They have specific properties relating to the size of these particles which may differ from those of the bulk material.
It has mass and occupies space.
All substances are made up of elements, compounds or mixtures.
Define pure substances.
Homogenous matter with a definite fixed composition.
Examples are both elements and compounds.
5 examples of pure substances.
Fe, N₂, CO₂, HCl, H₂O
Pure substances made entirely of atoms of one element.
Cannot be separated into similar substances by chemical change.
4 examples of elements.
Ne, Al, Br₂, S₈
Pure substances composed of two or more different elements chemically combined in fixed proportions.
4 examples of compounds.
CO₂, HF, C₆H₁₂O₆, H₂O
A substance that contained 2 or more pure substances.
Also called homogeneous mixtures.
A mixture of constant bc imposition and properties throughout.
4 examples of solutions.
Air, seawater, stainless steel, smoke
Define heterogeneous mixtures.
Mixtures that have variable composition and properties throughout.
3 examples of heterogeneous mixtures.
Granite, soil, concrete
Substances that exist before a chemical reaction.
Substances formed as a result of a chemical reaction.
A group of atoms bonded together, forming a small independent group.
Both elements and compounds exist as molecules.
2 examples of molecules.
Define physical properties.
Properties of a substance that can be determined without changing the chemical composition.
3 examples of physical properties.
Boiling point, odour, colour
Define chemical properties.
Properties of a substance that relate to the ability of the substance to form new substances.
3 examples of chemical properties.
Ability to react with water, oxygen or acids
Define boiling point.
The temperature at which the vapour pressure of a liquid is equal to surrounding atmospheric pressure.
Define melting point.
The temperature at which a solid changes state into a liquid
A measure of how resistant solid matter is to various kinds of permanent shape change when a force is applied.
The ability of any substance to dissolve in a solvent to form a homogenous solution.
A measure of the ability of a substance to conduct an electric current.
The ability of a material to be beaten into a sheet.
Metals tend to be malleable, other materials tend do be brittle.
The ability of a material to be drawn in to a wire.
The ability of a substance to reflect light.
The mass per unit volume of a substance.
Equation for density.
Density = mass ÷ volume
⍴ = m ÷ v
Measured in kg/m³ or kg/L
Define chemical change.
Changes in which new substances with different compositions and properties are formed. These are usually irreversible.
2 examples of chemical change.
Hydrogen Peroxide decomposing, burning Propane
Define physical change.
A change only to physical properties, no change is made to the composition of the substance.
2 examples of physical change.
Substances dissolving, substances evaporating
Define filtration and crystallisation
Allows mixtures of an insoluble solid to be separated from a soluble solid
What physical property are filtration and crystallisation based on?
How does filtration and crystallisation work?
Mixture added to solvent such as water
Passed through filter paper
Insoluble material retained on filter paper
Soluble material able to pass through
3 examples of filtration and crystallisation.
Sugar from sand, mud from water, dust from air
What physical property is distillation based on?
Differences in the boiling points of the different substances.
How does distillation work?
In mixtures of liquids:
Mixture is heated
Liquid with lowest boiling point boils first
Vapour is collected and condensed
2 examples of distillation.
Crude oil being separated into fuels, alcohol being distilled
What physical property is chromatography based on?
The size of the particle or the degree with which the particle is attracted to the stationary phase.
How does chromatography work?
Mixture is passed in a mobile phase through a stationary phase.
Example of chromatography.
Separating inks using water rising up through filter paper.
Used to separate mixtures of a liquid and an insoluble solid.
How does decanting work?
Liquid is carefully pored from the insoluble sediment at the bottom of the container.
Often separation is incomplete and small amount of solution is left behind in the container.
2 examples of decanting.
Wine from sediment, water from a soil solution
Pure substances with distinct measurable properties or mixtures with properties dependent on the relative amounts of the substances that make up the mixture.
What are chemical bonds caused by?
Electrostatic attractions that arise as a result of the sharing or or transfer between participating ions.
The measure of the bonding capacity of an atom.
Atoms or groups of atoms that are electrically charged due to a loss or gain of electrons.
Define octet rule.
When other elements react to form bonds, they do so in such a way as to obtain an inert gas electron configuration, that is, achieve the stability by having a full valence shell.
Describe metallic bonding.
It is non directional bonding.
The electrostatic attraction must be overcome if a metal is to melt/boil.
The more valence electrons, the higher the attraction, therefore higher melting/boiling point
Describe ionic bonding.
Electrostatic attraction between positive metal ion and negative metal ion.
Attraction must be overcome before melting/boiling can occur.
Large charge can lead to stronger attraction, hence a higher melting/boiling point.
Describe covalent bonding.
Shared electrons between non-metal atoms.
Attraction is between the positive nuclei on either side if the shared electrons.
Strong intramolecular forces between atoms.
Weak intermolecular forces between molecules therefore low melting/boiling point.
Define ionic compound.
A substance formed from a cation and an anion.
Define simple ion.
A single element with a charge.
A positive ion.
A negative ion.
Define polyatomic ion.
More than 1 element in a compound with an overall charge.
What are ionic compounds produced by?
The combinations of Metal and Ammonium ions with non-metals.
What do ionic compounds consist of?
Positively charged, metallic ions with negatively charged, non-metallic ions.
How are the ions in ionic compounds arranged?
In a neutral, crystalline lattice or framework.
Each positive ion is surrounded by a fixed number of negative ions.
Each negative ion is surrounded by a fixed number of positive ions.
How are the ions held together in ionic compounds?
The ions are in fixed positions.
The positive cations stick to the negative anions by electrostatic forces.
These are called ionic bonds.
Overall charge is 0.
Define continuous lattice.
When bonding like metallic or ionic continued throughout the whole structure.
List the 4 physical properties of ionic substances.
Rigid or brittle
High melting/boiling point because of strong forces between ions
Conductivity:solids don't conduct electricity. Substances dissolved in solution and molten substances do conduct electricity
Why can molten ionic compounds conduct electricity but solid ionic compounds can't?
Ionic compounds can only conduct electricity if their ions are free to move.
Which type of elements tend to form ionic compounds? Why?
Metals and non-metals
Metals like to lose electrons, non-metals like to gain electrons
How can metallic bonding be modelled?
As a regular arrangement of forces of attraction between the nuclei of these atoms and their delocalised elections which are mobile.
What can the metallic bonding model be used to explain?
The physical properties of metals.
Why can covalent bonding be modelled?
The sharing of pairs of electrons result in electrostatic forces of attraction between the shared electrons and the nuclei of adjacent atoms.
What are the 5 physical properties of metals?
Good conductors of heat and electricity
High melting/boiling point
Malleable and ductile
What does a high density mean?
Many atoms are tightly packed together
What do malleability and ductility indicate?
The cations have cushions of electrons so they have a stronger attraction
What does high electrical conductivity indicate?
The metallic structure has mobile electrons
How are the properties of covalent network substances explained?
Modelling covalent networks as three-dimensional structures that comprise of covalently bonded atoms.
How can the properties of covalent molecular substances be explained?
The absence of mobile, charged particles in their molecular structure.
Describe the conductivity of covalent structures?
When solid or molten they cannot conduct heat or electricity.
Some are able to conduct in aqueous solution (eg HCl)
Why are some covalent structures able to conduct heat and electricity in aqueous solution?
They can react with water and form ions.
These ions can then carry charge.
Describe melting/boiling point of covalent structures.
Why do covalent structures have a generally low melting/boiling point?
The forces of attraction between molecules are weak.
What physical properties are often found from solids formed from molecules.
They are often soft or brittle.
How to find the percentage composition.
% A in compound = w × relative atomic mass of A over relative formula mass of a compound (molecular) × 100
% B in compound = z × relative atomic mass of B over relative formula mass of a compound (molecular) × 100
Define organic chemistry.
The study of the many compounds which are based on the element Carbon.
What is the name of the two elemental forms of Carbon.
What are the two elemental forms of Carbon?
Diamond and Graphite
What molecular shape do single atom Carbon compounds have?
An organic compound made of only Carbons and Hydrogen
How are Carbohydrates different to Hydrocarbons?
Carbohydrates contain C, H and O
Define Aliphatic Hydrocarbons.
Compounds of Hydrogen and Carbon that form long chains and do not form rings.
Define Alicyclic Hydrocarbons.
Compounds of Hydrogen and Carbon that contain one or more Carbon rings.
Define Aromatic Hydrocarbons.
Compounds that contain Benzene as a part of the structure.
A Cyclic Hydrocarbon with the formula C₆H₆
What are the 3 main groups that Aliphatic Hydrocarbons can be divided into?
Aliphatic Hydrocarbons that contain only single Carbon to Carbon bonds.
Aliphatic Hydrocarbons that contain one or more Carbon to Carbon double bonds.
Aliphatic Hydrocarbons that contain one or more Carbon to Carbon triple bonds.
Define Saturated Hydrocarbons.
Molecules that only contain single Carbon to Carbon bonds and a maximum amount of Hydrogen atoms bonded to the Carbon atoms present (Alkanes)
Define Unsaturated Hydrocarbons.
Molecules that contain one or more Carbon to Carbon triple bonds and could hold more Hydrogen atoms (Alkenes and Alkynes)
What are the 2 types of reactions that Alkanes undergo?
Define Alkane substitution reactions.
A reaction between an Alkanes and a Halogen where one or more Hydrogen atoms are substituted by a Halogen atom.
General equation for Alkane substitution reactions.
Alkane + Halogen ➝ Halogenated Alkane + Hydrogen Halide
Define Alkane combustion reactions.
When Alkanes are ignited in the presence of O₂
What are the 2 possible reactions that can occur in Alkane combustion reactions?
What does an excess O₂ reaction produce?
CO₂ and H₂O
What does a limited O₂ reaction produce?
CO and H₂O
Define structural isomer.
A compound with the same molecular formula but different structural formula.
What is the prefix cis?
When the Hydrogens are across from each other.
What is the prefix trans?
When the Hydrogens are diagonal to each other.
What are the two reactions that Alkenes can undergo?
Combustion (same as Alkanes) and Addition
Why are Alkenes more reactive than Alkanes?
The double bond can be broken. This frees 2 electrons that allow bonding with other atoms.
What is the characteristic reaction for an Alkene?
Define Hydrogenation reactions.
Where Alkenes are converted to Alkanes by the double bond breaking and each Carbon atom bonding with a Hydrogen atom.
General equation for Hydrogenation reactions.
Alkene + H₂ ➝ Alkane
Define Halogenated reactions.
When a Halogen reacts with an Alkene, Halogen atoms are added across the double bond.
Define Markownikoff's rule.
The Hydrogen atom of an acid which reacts with a Hydrocarbon will bond with the Carbon with the most Hydrogens already attached.
You must apply this rule to all Hydrohalogenation and Hydration reactions.
Define Hydration reactions.
Where water reacts in the presence of concentrated Sulphuric acid as a catalyst to produce alcohol.
What are the two reactions Aromatics can undergo?
Combustion and substitution
What are the tree types of substitution reactions Aromatics can undergo?
Define Halogenation substitution aromatic reactions?
Benzene can be halogenated by the addition of a halogen and a suitable catalyst.
Define Nitration reactions.
Benzene can have a nitro group added by the addition of Nitric acid and Sulphuric acid as a catalyst.
Define Alkylation reactions.
Benzene can have an alkyl group added by the addition of a chloroalkane in the presence of Aluminium Chloride as a catalyst.