chemistry unit 2

keyterms and definitions

bulk properties

-consideration of the whole mass of material
-strength, elasticity, etc

conductor

a material which contains charged particles, which are free to move or carry electrical energy

covalent bond

a pair of electrons between non metals

diamond

a giant covalent structure which is made up of carbon atoms, each of which form 4 covalent bonds with 4 other carbon atoms.

electrostatic force

strong forces between oppositely charged ions

fullerines

molecules of carbon atoms with hollow shapes. Structure based of hexagonal rings of carbon atoms but may also contain five or seven carbon atoms.

giant covalent structure

A structure with many atoms joined to each other by lots of strong, covalent bonds giving a high melting point and (except for graphite) poor electrical conductivity.

Graphene

This is a single layer of graphite.

They have interlocking hexagonal rings of carbon, one atom thick, so therefore very thin.

Excellent electrical conductivity, and is used in electronics and computer chips.

What type of structure is graphite?

A giant covalent structure

What element is graphite made up of?

Carbon atoms

How many covalent bonds does each carbon atom in graphite form?

Three covalent bonds

What shape do the layers of carbon atoms in graphite form?

Hexagonal rings

Are there covalent bonds between the layers of graphite?

No, there are no covalent bonds between the layers

ion

An atom or group of atoms that has a positive or negative charge.

how does a positive ion form

when an atom loses an electron

how does a negative ion form

when an atom gains an electron

Ionic bonds

Formed when one or more electrons are transferred from one atom to another

ionic compound

chemical compounds formed of oppositely charged ions, held together by electrostatic forces

lattice

Regular arrangement of particles. (occurs in crystal structures)

malleable

capable of being shaped, metals are malleable because the uniform layers of atoms can slide over one another.

metallic bond

the attraction of a metallic cation for delocalized electrons

nanoparticles

Nanoparticles have diameters between 1 nm to 100 nm in size. Nanoparticles can exhibit properties different to those for the same material in bulk.

What type of bonds do simple molecules have?

Very strong covalent bonds

What type of forces exist between simple molecules?

Very weak intermolecular forces

What is the melting and boiling point characteristic of simple molecules?

They have low melting and boiling points

Why do simple molecules not conduct electricity?

There are no free electrons

smart materials

Materials which change in response to their surroundings, such as light levels or temperature.

acid

A substance that increases the hydrogen ion concentration of a solution.

alkali

A base that dissolves in water

neutralisation

A reaction of an acid with a base, forming a salt and water

What is the pH scale used for?

To measure the concentration of H+ ions in a solution.

What pH range indicates an acidic solution?

A pH of 0 to 7.

What pH value is considered neutral?

A pH of 7.

What pH range indicates a basic solution?

A pH of 7 to 14.

precipitation reaction

a reaction in which an insoluble substance forms and separates from the solution

What is titration?

A process in which a solution of known concentration is used to determine the concentration of another solution.

What is one application of titration?

Preparing crystals of a soluble salt.

weak acid

an acid that is only slightly ionized in aqueous solution e.g ethanoic acid

alloys

mixtures composed of two or more elements, at least one of which is a metal

anode

a positive electrode at which oxidation occurs

cathode

a negative electrode at which reduction occurs

electrode

A metal strip that conducts electricity

dilute

containing a small amount of H+ particles in a large amount of acid

concentrated

a high amount of H+ particles relative to the amount of water

strong acid

completely dissociates in water and a negative ion

weak acid

an acid that releases few hydrogen ions in aqueous solution

test for hydrogen

Squeaky pop

test for carbon dioxide

extinguishes flames

oxygen gas test

Relights a glowing splint

What solution is used to test for sulfates?

Barium chloride solution

What should be added first when testing for sulfates?

Dilute hydrochloric acid

What indicates the presence of sulfates in a test?

A white precipitate (Barium sulfate) will form

oxidation

the gain of oxygen

reduction

the loss of oxygen

what happens to iron in the blast furnace

it is oxidised from fe2 to 2fe

electrolysis

the method used which involves using electricity to split compounds apart

alloy

A mixture of two or more metals

properties of iron/steel

cheap, strong, malleable

properties of aluminium

Strong, low density, good conductor of heat and electricity, resistant to corrosion

properties of copper

Ductile, malleable, good conductivity

properties of titanium

hard, strong, low density, resistant to corrosion, high melting point

precipitate

a solid that forms from a reaction of 2 liquids

how to identify iron 3

rust brown jellylike precipitate

how to identify iron 2

green jellylike precipitate

how to identify copper

blue jellylike precipitate

what is bond energy

average energy required to break a bond

what change is bond breaking when exothermic

energy change is negative

what change is bond breaking when endothermic

energy is positive

hydrocarbons

a family of molecules containing carbon and oxygen

crude oil

a mixture of hydrocarbons. extracted from within the earth.

what bonds does (-ane) have

c-c and c-h

what is the general formula of an (-ane)

CnH2n+2

what bonds does an (-ene) have

c=c, c-h and c-c

what bonds does an (-ol) have

c-h. c-c, -oh

what bonds does on (-oic acid) have

-c, =o,-oh, c-c, c-h

example of an (-ane)

ethane

example of an (-ene)

propene

example of an (-ol)

ethanol

example of an (-oil acid)

ethanoic acid

will alkanes react with bromine water

no

will alkenes react with bromine water

yes, water will change from orange to colourless.

how do you test for alcohol

use acidified potassium dichromate. if alcohol is present the dichromate will change from orange to green when heated