S1-L1 Elements, Compounds & Mixtures Flashcards
What is “matter”?
- Anything that has mass
- all objects made of matter
- single chemical substance/complex mix of substances
Outline the states of matter
-Solid/ liquid/ Gas
State the processes taking place when changing from a solid to liquid to gas and vice versa as well as solid to gas and gas to solid
- melting–>vaporisation
- condensation–>freezing
- solid to gas–> sublimation
- gas to solid–> deposition
What physical changes take place when changing from steam-water-ice and vice versa
- condensing/liquefying–>freezing/solidifying
- evaporating/boiling–> melting/fusing
Define the following properties of matter:
1-Electrical conductivity 2-Heat conductivity 3-Desnity 4-M. Point 5-B. Point 6-Refractive Index 7-Malleability 8-Ductility
1-Ability to transmit electricity-like copper use in electrical wiring
2-Ability to transfer heat energy-like aluminium saucepan
3-mas:volume ratio like lead weights
4-temp when solid turns to liquid-like 0 degrees for water
5-temp when liquid becomes gas-like 100 degrees for water
6-way light passes through material bent-like 1.33 for H2O
7-ability to be shaped via hammering-like gold jewellery
8-ability to shape via puling in to wire-like tantalum-dentist instrument
Define the property “intensive” and outline example(s)
- Not dependent on amount of matter present
- could use to identify substance
- like density/ colour/ b. point
What are “extensive” properties and give some example(s)?
- Dependent on amount of matter present
- like mass/volume/weight
Describe what “physical” properties are and how they arise
- Observed by examining pure substance
- arise from molecular structure & intermolecular force’s strength
What are “chemical” properties and how do they arise?
- Observed during chemical reaction
- Arise from e- distribution around atom’s nucleus–> particularly outer (valence) e-‘s
Outline and describe “pure” substances
- Fixed set of physical + chemical properties
- can’t separate via physical processes
- properties not vary
- can only change via chemical reaction
Briefly explain what a “mixture” is
- 2 or more substances physical blend
- variable composition
- different properties for different compositions
- can separate mixture in to separate components via physical process
Define an “element”
- simplest form of matter which has unique properties
- can’t split substance in to two/ more simpler substance via chemical method
- ->like H or O
What is a “compound” and give an example?
- compounds contains two/ more chemically bonded elements in fixed proportion
- like H2O
What are “molecules” and describe them?
- most matter made up of molecules/mixture of them
- group of 2+ atoms joined together
- element can exist as atoms/molecules but compounds made of molecules
Outline a summary of Dalton’s atomic theory
- Elements combined in fixed ratios
- all matter composed of atoms
- different elements have different atoms types
- ->can characterise by atomic weight/ all same elements identical
- can create/destroy atoms
- compounds composed of 2+ atoms chemically combined in fixed proportions
- ->like H2O ratio: 2H + 1 O
- chemical reactions rearrange atoms–>changing chemical combination so identity of atom changes.
Briefly explain the following properties of atoms:
1) Mass
2) Combining power
1) -Almost all atom’s mass contained in nucleus
- protons/ neutrons/ electrons
2) -ability to form chemical bonds
- also termed valency
Structure of atom:
1) Describe the structure of the atom including the nucleus
1) -Proton (+) charged
- neutron uncharged
- nucleus surrounded by e-‘s (-) charged
- e-‘s in outermost orbital determine atom’s chemical and electrical properties
Define the “nucleons” of an atom
-Is the n. of protons and neutrons in the nucleus which is the atom’s mass number
Describe the meaning of “combining power”-valency
- Ability of atom to combine with other atoms controlled by n. of e-‘s
- ->which atom will give/take/share to form chemical compound
- relates to n. of e-‘s AND electron’s spaces in atom’s electron shells
What are “chemical symbols”?
- abbreviation/short-hand form of chemical element used in formulae
- consists of capital letter and sometimes followed by small letter
- examples: H/ O/ He (Helium)
Where are chemical names/symbols derived from and give some examples?
- From their Greek/ latin names
- examples:
- Chlorine-Greek for yellowish green; Cl
- Helium- Greek for sun; He
- Calcium-Latin for lime; Ca
- Carbon-Latin for charcoal; C
- Iron- Anglo-Saxon; Fe (Latin)
Define and describe “Relative Atomic Mass (Ar)”
- Defined as mass of one atom of element divided by mass of 1/12 of atom of C-12
- Ar of chemical element gives atom’s weight which is force makes when gravity pulls on it
- written as subscript before atom’s symbol like 1^H
Describe what “molecules” are
- Unit of 2+ atoms held together by chemical bonds
- contains atoms in defined proportions like water
- -> 2 H and 1 O
What is “molecular formulae”?
- Show n. of atoms found in 1 molecule of substance
- ->like sugar: glucose contains 6C’s/ 12 H’s and 6 O’s
- ->written as C6H12O6
Outline the terms “Relative Molecular Mass (Mr)”
-Gives mass of molecule relative to that of 12C atom which taken to have mass of 12
What is the relative molecular mass formula and how do you calculate it (give an example)?
- Mass of 1 molecule substance/ (1/2 X mass of 1 atom of C-12)
- RMM calculated by summing atomic masses of atoms in molecule
- Example: H2O- (2 x H) = H2O
- -> (2 x 1) + (16)= 18
Describe what a general mixture is
- Variable composition
- components retain characteristic properties
- separable in to pure substances via physical methods
- mixtures of different compositions may have widely different properties
What does it mean when a mixture is described as “homogeneous”?
- Single phase
- same properties throughout mixture with uniform appearance
- such as a solution
Outline what a “heterogeneous” mixture is
- Multiple phase
- variable properties with non-uniform appearance
- colloids visually homogeneous BUT microscopically heterogeneous
Describe a “colloid”
- Phase separated mixture in which one substance of microscopically dispersed insoluble/soluble particles suspended throughout another substance
- sometimes dispersed substance alone called colloid but term refers to overall mixture
Give a definition and description of a “solution”
- Type of homogeneous substance formed when one substance dissolved in another
- best mixed out of all “mixtures”
- always has substance dissolved & substance which does dissolving
- ->substance which dissolves solute
- ->substance which does dissolving in solute
What property does the separation of mixtures rely on?
-Use differences in physical properties
Briefly outline the following basic separation techniques:
1-Filtration 2-Crystallisation 3-Extraction 4-Distillation 5-Magentisation 6-Chromotography
1-select components by particle size (solid/liquid)
2-select components by solubility (solid from solution)
3-select components by solubility (solid/liquid from solution)
4-select components by b. point (liquid-liquid)
5-magnetic metal from other components
6-select components by affinity for stationary point
What is “thin-layer chromatography”?
- Technique used to separate non-volatile mixtures
- performed on sheet of glass/ plastic/ aluminium foil
- ->which coated in thin layer of adsorbent material like silica gell
Outline a key use of thin-layer chromotography
-Analysis of common over counter (OTC) cough-cold prep
Summary of lecture
- Elements–>compounds
- Atoms–>molecules
- Symbols–> Formulae
- Sum of Ar–> Mr
-Uniform properties–> yes–> fixed composition–>yes –> chemically decomposable–> yes –> compound
- No uniform properties–> heterogeneous mixture
- No fixed composition–> homogeneous mixture
- Not chemically decomposable–> element
