Test Week 3

Question 1

KINETIC THEORY

Answer 1

• Model about the structure of cases used to explain from of these common physical properties and behaviours
• First comprehensive version of this theory was printed in 1857 by RUDOLF CLAUSIUS
• Model states; gases are composed of particles have rapid constant motion
• No attractive force (attraction and repulsion)
• No fixed volume
• Collide at high speed
• Collisions are highly elastic
• KINETIC ENERGY and TEMPERATURE are proportional

Question 2

GAS

Answer 2

• Always take the shape of their container
• Very low density
• Exert pressure
• Can be compressed
• Readily diffuse through other gases

Question 3

IDEAL GAS

Answer 3

• No volume
• No attraction
• Never condense as particles don’t have volume

Question 4

REAL GAS

Answer 4

• Has volume
• Have forces of attraction
• Condense to form liquid

Question 5

HOMOGENEOUS

Answer 5

• Uniform composition
• Particles of the material are spread evenly throughout its entire volume
• Eg. Copper, Distilled Water, Mineral Water, Air

Question 6

HETEROGENEOUS

Answer 6

• Variable compostion
• Different particles that make up the mixture are distributed in distinct clumps within the substance
• Eg. Blood, Sugar dissolved in Water, Vinegar, Orange Juice, Alka-Seltzer tablet

Question 7

ELEMENT

Answer 7

• Substance that cannot be broken down into simpler substances by chemical means.
• Composed of atoms that have the same atomic number (same number of protons in its nucleus as all other atoms of that element)

Question 8

COMPOUND

Answer 8

• Pure substance
• Have fixed composition
• Consist of two or more different elements that are chemically combined in a definite whole number atomic ratio

Question 9

MIXTURE

Answer 9

• Can be separated by physical means
• When mixed, individual substances keep their properties in a mixture, while if they form a compound their properties can change
• There is little or no energy change when a mixture forms
• Variable compositions

Question 10

SOLUTION

Answer 10

• Homogeneous mixtures like sea water, H20 and brass are SOLUTIONS

Question 11

MOLECULES

Answer 11

• Things like H20 and C02

- MOSTLY made up of non-metals

Question 12

IONIC COMPOUND

Answer 12

• Metal and Non-Metal
• WHEN WRITING; put metal first (as its a cation)
• Eg. NaCl
• DONT PUT PREFIX

Question 13

METALLIC BONDING

Answer 13

• Between metals

Question 14

COVALENT

Answer 14

• Between 2 non metals
• WHEN WRITING; lowest group eg. CO2 not 02C
• Don’t use mono prefix for first element
• MONOXIDE NOT MONO OXIDE
• Shorten last element to ‘ide’
• Eg. N3Cl (Trinitrogren Chloride)

Question 15

COVALENT MOLECULAR

Answer 15

• 2 NON METALS
• PUT PREFIX ON FIRST ELEMENT EXCLUDING MONO
• A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms
• The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding.

Question 16

COVALENT NETWORK

Answer 16

• GRAPHITE, DIAMOND AND SILICON DIOXIDE
• A network solid or covalent network solid is a chemical compound (or element) in which the atoms are bonded by covalent bonds in a continuous network extending throughout the material
• In a network solid there are no individual molecules, and the entire crystal may be considered a macromolecule

Question 17

JOHN DALTON (1766 - 1844) English Teacher & Scientist

Answer 17

• 1803 - 1808 published a precise definition of atoms THE ATOMIC THEORY

Question 18

THE ATOMIC THEORY

Answer 18

• Elements are composed of extremely small particles; atoms
• All atoms of a given element are identical; same size, mass and chemical properties
• Atoms of different elements have different size, mass and chemical properties
• Atoms are not created nor destroyed, or changed into different types during a chemical reaction
• Chemical reaction involves only SEPARATION, COMBINATION OR RE ARRANGEMENT of atoms
• Compounds are formed when atoms of more than one element combine in a specific atom

Question 19

J.J THOMPSON

Answer 19

• Matter was known to be electrically neutral
• Negative particles which made up cathode rays (ELECTRONS) has a mass of 1/1000(th) that of the smallest atom
• Proposed new model for the atom; PLUM PUDDING
• Model consisted of numerous small negatively charged electrons imbedded within a much LARGER uniform positively charged sphere
• WAS SHORT LIVED BY RUTHERFORD

Question 20

ERNEST RUTHERFORD (1871 - 1937) Physicist

Answer 20

• Proposed improved model (from Rutherford) of the ATOM that would account for his experiment observations
• Proposed the atom consisted mostly of empty space occupied by a very low mass of electrons
• The electrons orbited a tiny central region he called the NUCLEUS
• EXISTENCE OF ATOMIC NUCLEUS
• Worked on radioactivity, coining the terms ‘alpha’ and ‘beta’ to describe the two different types of radiation emitted by uranium and thorium
• He also observed that radioactive material took the same amount of time for half of it to decay, known as its “half life”
• That alpha particles through the gold foil deflected passed in the region where little electrons were

Question 21

SIR JAMES CHADWICK (1891 - 1974)

Answer 21

• Identified the neutrons as the product of alpha particle bombardment
• Finally accounting for the atoms mass (Rutherford model didnt have this)
• Awarded the Hughes Medal of the Royal Society in 1932
• Nobel Prize for Physics in 1965

Question 22

NIELS BOHR

Answer 22

• Modified Rutherfords model, solving problem of unstable electron orbits and accounting for the line of spectrum of hydrogen gas
• Proposed that electrons moved about the central nucleus in circular orbits
• Electron COULD orbit without loosing energy

Question 23

CURRENT ATOMIC MODEL

Answer 23

• Central nucleus where neutrons and protons are
• Electrons orbit within regions of characteristic electron distribution
• Electrons are tiny

Question 24

SPECTRAL ANALYSIS

Answer 24

• The analysis of a spectrum to determine the properties of its source, such as the analysis of the emission spectrum of a substance to determine the electron distribution in its molecul

Question 25

PURE SUBSTANCE

Answer 25

- Having fixed or constant composition - Not being able to separated into other substances by physical means - Well defined and constant boiling point and melting point

Question 26

SIEVING (PHYSICAL)

Answer 26

- Used to separate the components of a mixture based on PARTICLE SIZE - Small particles pass through, whilst coarser grains don't - Unlikely to produce pure substances

Question 27

FILTRATION AND EVAPORATION

Answer 27

- Used to separate the substances in a mixture based on their differing solubility and volatility - Other forms of filtration; micro filtration, ultrafiltration and nano filtration

Question 28

GRAVITY SEPARATION

Answer 28

- Suitable for separating (or concentrating) components in a mixture based on their densities - Effective when the components in the mixture have BIG DIFFERENCES IN DENSITIES e.g gold

Question 29

DISTILLATION

Answer 29

- Used to separate a mixture based on boiling point differences in individual components of the mixture - Process can be used to produce distilled water from sea water