Physical & chemical changes

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Information about Physical & chemical changes
Education

Published on July 3, 2013

Author: kwarne

Source: slideshare.net

Description

PowerPoint slideshow to teach physical and chemical changes to grade 10

SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Physical & Chemical Change K Warne

SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Phases of MatterPhases of Matter PLASMAPLASMA+ + + + + + The FOUR states of matter are determined by the amount of ………………….…………………. available.

SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe

SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Melting (Fusion) When a solid melts the particles need to undergo a number of changes: Solid --> Liquid: – the spaces between the particles increase – The energy of the particles increases – The forces between the particles are weakened Each of these changes requires energy to be put in. The temperature stays constant because the extra energy is being used to weaken the forces. Melting

SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Boiling vs Evaporation Wind Water molecules (high energy) escape from the surface of the liquid. The remaining particles have less energy - lower temperature ENERGY IS REMOVED FROM THE WATER (Cooling Effect). All liquids have their own vapour (gas). This vapour has a pressure which increases with temperature. When the vapour pressure equals the pressure outside the liquid the liquid boils. GAS LIQUID IN BOILING ENERGY MUST BE PUT IN. The temperature of the water does not change as the energy is used to change the phase.

SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Intermolecular Forces broken! Phase Changes Wind Forces between particles (intermolecular) breaking. GAS OH H OH H OH H O H H OH H Bonds inside particles (intramolecular) do NOT break! Boiling & evaporation are both phase changes – intermolecular bonding is involved (broken or formed) in phase changes – intramolecular bonding is not affected! Molecule escapes! High energy molecules escape!

SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Boiling vs Evaporation Boiling Evaporation Similarities • Change water to water vapour • Particles undergo same changes (increase spaces, energy, weaker forces) Differences • High Temp • Energy put in • Affected by atmospheric pressure • Low Temp • Energy taken out. • Not affected by pressure.

Consider the following analysis of different samples of table salt (NaCl) , what do you notice? Sample no. Sample mass Mass of Na Mass of Cl % Na %Cl 1 117g 46g 71g 46*100 117 =39.3 % 2 468g 184g 284g 184*100 284 3 59g 23g 36g 1. 117g (46g Na & 71g Cl)

The Law states: A certain chemical compound always contains the same elements chemically combined in the same proportions by mass. NaCl CaCl2 KMnO4 K2Cr2O7 Ratios: 1:1 1:2 1:1:4 2:2:7 These ratios never change. NaCl is always 1:1 and 23g:35,5g – irrespective of whether the NaCl comes from the UK, USA or SA.

SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Conservation of Mass, Atoms & Molecules • Show that mass, atoms are conserved but molecules are not 2H2 + O2  2H2O 2H2 O2 2H2O Atoms 4 2 = 6 6=6 Conserved Mass 4 32 = 2x18 36=36 Conserved molecules 2 1 = 2 3≠2 Not conserved!

SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe REACTIONS Hydrogen and oxygen react to produce water. (Synthesis reaction) H2 + O2  H2O Ar: H = 1, O = 16 Mr: H2 =2, O2 = 32 H2O = 16+2=18 Balanced Eqn: 2H2 + O2  2H2O LHS: RHS: 2(2) + 32 = 36 2(2+16) = 36 LHS = RHS MASS is CONSERVED!! This is true for ALL REACTIONS. This is the reaction used to power the space shuttle.

SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe REACTIONS 1. Butane reacts with oxygen 2. Carbon dioxide and water are formed Butane + Oxygen ---> Carbon dioxide + water 2C4H10 + 13O2 ---> 8CO2 + 10H2O 1 2 Reaction equation BALANCED!

SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Balancing Reactions 1. 2Na + Cl2 --> 2NaCl 2NaCl: 2(23+35.5) = 2(58.5)=117g 1.2x10-6 1. C + 2Cl2 --> CCl4 ............................................................................ 1. 2ZnS + ...O2 --> ...ZnO + ...SO2 ............................................................................ 1. FeS + ...HCl --> H2S + FeCl2 ............................................................................ 1. SO2 + ...H2S --> ...S + ...H2O ............................................................................

SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Balancing More Reactions 1. Na + H2O --> NaOH + H2 2. H2 + O2 --> H2O 3. CaCO3 --> CaO + CO2 4. CaCl2 + Na2SO4 --> CaSO4 + NaCl 5. Al(NO3)3 + K2CO3 --> Al2(CO3)3 + KNO3 6. Na3PO4 + MgI2 --> Mg3(PO4)2 + NaI

SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe BALANCING REACTIONS 1. Butane reacts with oxygen 1 2 Reactants Substance O C H No. oxygen 26 13 butane 0 8 20 2 TOTAL 26 8 20 2. Carbon dioxide and water are formed Products Substance O C H No. Carbon dioxide Water TOTAL butane

SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Hi - This is a SAMPLE presentation only. My FULL presentations, which contain loads more slides and other resources, are freely available on my resource sharing website: www.sciencecafe.org.za (paste into your browser if link above does not work) Have a look and enjoy! Keith Warne

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