Flashcards

CHEM Chapt 1,2 & 3

ws_ 149 O'Level Sciences English 55 cards

Cards in this deck (55)

1CHAPTER 1: Kinetic Particle Theory...
21. Characteristics of Particles in Different States: (a) ArrangementSOLID → closely packed in an orderly manner
LIQUID → closely packed in an disorderly manner
GAS → particles are far apart in random arrangement
31. (b) DrawingSOLID | LIQUID | GAS
41. (c) Attractive forces between particlesSOLID → very strong
LIQUID → strong
GAS → very weak
51. (d) Kinetic energy of particlesSOLID → very low
LIQUID → low
GAS → high
61. (e) Motion of particlesSOLID → Only vibrate about their fixed positions, cannot move freely ; fixed shape
LIQUID → Not held in fixed positions, can move freely throughout liquid & slide over one another ; no fixed shape
GAS → Not held in fixed positions, move about rapidly in any direction ; no fixed shape
71. (f) Able to compress?SOLID → No, particles are already very close to one another ; fixed volume
LIQUID → No, particles are still packed quite closely tgt
GAS → Yes, large space btwn particles allow gas to be easily compressed when pressure is applied, particles can be forced to move closer tgt ; no fixed volume
82. Melting process *Answering technique: 1) Heat → KE 2) Solid arrangement & movement 3) Completely overcome f.o.a 4) Liquid arrangement & movement1) Heat energy is absorbed by the particles of the solid. Heat energy is converted into kinetic energy. Particles start to move faster about their fixed positions
2) When the temp is high enough, vibrations of the particles become high enough to overcome the f.o.a between the particles. Particles begin to break away from their fixed positions.
3) Particles are no longer held in their fixed positions & substance is now a liquid. Particles can move freely throughout the liquid.
92. Melting graphA-B: Solid heats up → Temp of solid increases until reaches m.p. At point B, solid naphthalene starts to melt
B-C: Solid melts → During melting, temp of naphthalene does not increase even though heating continues. Heat energy taken in by particles is used to overcome the f.o.a holding the particles in fixed positions. Mixture of liquid + solid
C-D: Liquid heats up → all solid naphthalene melted. Temp of liquid increases as heating continues
103. Freezing process1) Energy is given out by particles of liquid. Particles lose KE & begin to move more slowly
2) When temp is low enough, particles no longer have enough energy to move freely. Particles settle into their fixed positions.
3) All particles settled into their fixed positions & substance is now a solid. Particles can only vibrate about their fixed positions.
113. Freezing graphP-Q: Liquid cools → Temp of naphthalene drops until f.p. is reached. From point Q, freezing begins
Q-R: Liquid freezes→ temp of naphthalene remains the same even as cooling continues. Heat energy is released as particles of the liquid are attracted to one another to form a solid. Mixture of solid + liquid.
R-S: Solid cools → At point R, all liquid naphthalene solidified. Temp. of solid drops as cooling continues.
124. Boiling process1) Heat energy is taken in by particles of the liquid & converted into KE & particles start to move faster as temp increases.
2) When temp is high enough, particles have enough energy to overcome the f.o.a that holds them tgt.
3) Particles are now spread out apart & substance is a gas. Particles are now moving freely & rapidly move in any direction.
134. Freezing graphW-X: Liquid heats up → Temp of naphthalene increases until b.p is reached. At point X, liquid starts to boil
X-Y: Liquid boiling → During boiling, temp of liquid does not increase even though heating continues. Heat energy is taken in by particles of liquid & used to overcome f.o.a btwn particles. Mixture of liquid + gas exists
Y-Z: Gas heats up → all liquid has boiled. Temp of water vapour increases as heating continues
145. Evaporation- Liquid changes into gas at a temp lower than b.p.
- Occurs because some particles have enough energy to escape asa gas from surface of liquid.
-Volatile liquids → liquids that evaporate quickly at room temp. Usually hv b.p. just above room temp.
155. Diff btwn boiling & evaporationBoiling occurs only at b.p. | Evaporation occurs at room temp
Boiling occurs throughout liquid | Evaporation occurs only at surface of liquid
Boiling occurs rapidly | Evaporation occurs slowly
166. Condensation-Gas changes to liquid
- When water vapour touches cold surface, condensation occurs & liquid water obtained
Process:
(1) Heat energy is given out by gas particles during condensation
(2) As temp. decreases, gas particles lose energy & move more slowly.
(3) Movement of particles become slow enough for gas to change into liquid
177. Sublimation & ***e.g. of solids that sublime-Solid changes directly to gas w/o going through liquid state
- Occurs bcos particles at surface of solid have enough energy to break away from solid & escape as gas
***E.g: Ammonium salts, iodine, carbon dioxide, naphthalene
Usefulness: changes directly from solid to gas w/o leaving any liquid behind
188. DiffusionDiffusion → movement of particles from a region of higher conc. to a region of lower conc., stops when equilibrium is reached.
198. ***Factors affecting diffusion(a) Relative molecular mass (Mr) → gases
(b) Temperature → liquid
208. (a) Effects of Mr (e.g.)- Rate of diffusion of gases is dependent on its Mr
*Gases with lower Mr diffuse faster than gases with higher Mr
E.g. Ammonia (Mr: 17 has a lower Mr than hydrogen chloride (Mr: 36.5). Hence, ammonia gas diffuse at a faster rate & travel a longer dist. than hydrogen chloride gas. Ammonium chloride is formed nearer to the end with hydrogen chloride.
218. (b) Temperature-Much slower than gases
*The higher the temp, the faster the rate of diffusion.
-Particles gain more KE as temp increases & move faster, which increases rate of diffusion.
22COMMON QNS: (1) Purple WB Pg 21-22 Q3) Porous pot qn (i) Gas Z is less dense than O2Water level at X → Increase, & eventually return to the same
- Gas Z diffuses into the porous pot faster than O2 diffusing out of porous pot.
- Higher amt. of gas in porous pot
- Thus, creating a higher pressure in the pot, pushing the water level down the tube. Water level at X increases
23(ii) Gas Z is more dense than O2Water level at X → decrease, & eventually remain to the same
- O2 diffuses out of the porous pot faster than Gas Z diffuses in
- Lower amt of gases in the pot
-Thus, creating a lower pressure in the pot, pulling the water level up the tube. Water level at X decreases.
24(iii) Why does the water level at X return to the same level after a while?The conc. of O2 particles & gas Z particles are the same in both the porous pot & the beaker. An equilibrium is reached & diffusion stops, although particles still continue to move.
25CHAPTER 2: Measuring & experimental techniques...
261. Apparatus to measure liquids- Measuring cylinder → to nearest cm3 (1dp)
- Burette → accurately measures to nearest 0.05cm3 (2dp), drop by drop
- Pipette → accurately measures out fixed volumes (e.g. 25.0cm3)
272. Apparatus to collect gasGas syringe → max vol. of 100cm3
283. Methods for collecting gas - 2 dependent factors)1) Solubility - how soluble gas is in water
2) Density - how dense gas is compared to air (Gas is less dense than air if Mr <30)
293. Methods1) Displacement of water: insoluble / slightly soluble in water
[Co2, H2, O2]
2) Downwards delivery: soluble in water & denser than air
[chlorine, hydrogen chloride]
3) Upwards delivery: soluble in water & less dense than air
[ammonia]
30Downward delivery:Upward delivery:
313. Solubility table ***
324. Drying gases - methods & examples
33CHAPTER 3: Separation & Purification...
341. Separating insoluble solid from liquidFILTRATION:
- Solid is separated from the liquid as filter paper acts as a sieve
- Liquid passes through the pores of the filter paper while solid remains on the filter paper as residue
- Residue → solid remaining on filter paper
- Filtrate → liquid /solution passes through the filter paper
352. Separating soluble solid from liquid (a)Evaporation to dryness → obtain soluble solid from a soln by heating soln until all water has boiled off.
- Solute + solvent → solution
(solid) (liquid)
- Add excess to ensure solvent is used up
-Solid obtained is not always pure
362. Separating soluble solid from liquid (b)CRYSTALLISATION → for solids that decompose on strong heating
- Water is removed by heating solution
-Heating is stopped when saturated soln is formed
-Dissolved solid forms pure crystals when cooled
1) Heat soln to evaporate water away so saturated soln is formed
2) Cool saturated soln & crystals will form
3) Filter mixture to obtain the crystals
4) Wash w. a little cold distilled & dry btwn 2 pieces of filter paper
373. Separating solids (a)SUBLIMATION → separate solids that can sublime from 1 that does not
E.g. CO2, naphthalene, iodine, NH4 salts
383. Separating solids (b) & (c)(b) USING MAGNETS → separate magnetic substance from non-magnetic substance
(c) Using a suitable solvent → if only 1 is soluble in a solvent
-Solvent → liquid that dissolved solid
- Solute → solid that dissolved in solvent
A solvent is used in which only 1 solid is soluble in it
394. Separating a liquid from a solutionSIMPLE DISTILLATION → separate pure solvent (liquid) from solution
Process of boiling liquid & condensing vapour
404. Simple distillation process1) In the distillation flask, the soln boils, vaporises, rises & enters the condenser.
2) In the condenser, water vapour cools & condenses back into pure water (distillate)
3) Pure water is collected as distillate in the receiver. Salt soln in the distillation flask becomes more & more concentrated as distillation continues. Solid residue of salt is left in flask
414. Simple distillation precautions1) Thermometer should be placed beside arm of distillation flask, shld not be dipped into the solution → ensures that thermometer is measuring the b.p. of substance being distilled
2) Condenser shld slope downwards → ensures pure solvent formed runs downwards
3) Cold running water enters water jacket from bottom of condenser & leaves at top → if water enters from top, it will exit before water jacket is completely filled. Thus, this ensures jacket is always completely filled to provide a more efficient cooling system.
4) If distillate is volatile, put receiver in a large container of ice → keep temp of distillate low so that it remains in liquid state
5) Boiling chips are placed in the distillation flask → ensures smooth boiling
424. Simple distillation graphAs salt soln is heated, temp increases. When soln boils, temp remains at 100० C until all water boils off
435. Separating immiscible liquids → do not mixSEPARATING FUNNEL → separate immiscible liquids with 2 diff densities.
446. Separating miscible liquids → mix tgtFRACTIONAL DISTILLATION → separate miscible liquids with 2 diff b.p.
- Liquid with lowest boiling point is first distilled over first
- Vapours of liquid with higher b.p. condense along fractionating column & fall back into round-bottomed flask
456. Fractional distillation process (Ethanol & water)1) Ethanol vapour & water vapour rise up column as soln is heated
2) Water vapour (higher b.p.) condenses in the fractionating column & falls back into flask
3) Ethanol (lower bp.) reaches upper part of fractionating column & distils over first
4) Thermometer shows constant temp of 78०C at this stage → b.p of ethanol
5) In condenser, hot ethanol vapour condenses into liquid ethanol as the running water cools it & flows into the receiver
6) Ethanol is collected as distillate in receiver
7) When all the ethanol is distilled over, temp increases to 100० C (b.p. of water)
Water distils over & is collected separately.
466. Fractional distillation graphs *know: (i) Temp vs time (ii) Conc vs time (iii) Temp vs vol of distillate-Temp of mixture increases until reaches 78० C
- At 78०C, ethanol distils over & temp remains the same until all ethanol distilled out of flask
- Temp then increases until 100 ० C & water is distilled over
- Temp remains unchanged as water is being distilled over
476. Role of fractionating columnFractionating column→ provides a larger SA for multiple condensation & evaporation so that the separation of liquids is more efficient
Liquid of higher b.p. can condense in column & fall back into flask while allowing liquid of lower b.p. to distill over first.
487. Separating components that dissolve in the same solventPAPER CHROMATOGRAPHY → Method of separation 2 or more components that dissolve in the same solvent
- Used to separate & identify mixtures
-Principle involved depends on the relative solubility of solutes in the same solvent which allows solutes to be separated..
497. Definition of Rf valueRf value / retention factor → ratio btwn the dist. travelled by the solute & the dist. travelled by the solvent
- Does not change as long as under the same conditions (same solvent & same temp)
- Allows us to easily identify substance on a chromatogram
507. Locating agentsLocating agent → chemical which reacts with a substance to produce a visibly coloured compound
-Spraying a locating agent allows coloured spots to be formed & identified.
517. Uses of chromatography1) Separate components in sample
2) Identify components present in a sample
3) Identify substances
4) Determine whether substance is pure
527. Precautions to take for chromatography1) Baseline is drawn in pencil → does not dissolve in most solvent & hence will not interfere with spots on chromatogram
2) Start line is above level of solvent → prevent sample from dissolving in the solvent & not be separated out
3) Spots are made small → prevent analytes from interfering with each other & become unclear
4) Solvent front must be near top of the paper → ensure complete separation of all components of the analytes on the chromatogram
5) Container is covered with a lid → saturate atmosphere within container so as to prevent evaporation of solvent
53Purity of substances is determined by 2 factors1) Exact & constant (or fixed) m.p. → a pure substance will have 1 fixed m.p.
2) Exact & constant b.p. → a pure substance will have 1 pure b.p.
54(1) Effect of impurities on m.p.Presence of impurities will:
-Lower m.p.
-The greater the amount of impurities, the lower the m.p. point
- Melting takes place over a range of temp
55(2) Effect of impurities on b.p.Presence of impurities will:
-Increase the b.p.
-The greater the amt of impurities, he higher the b.p.
-Cause substance to boil over a range of temp