Learning and Teaching Resources on Practical for Chemistry ...LEARNING AND TEACHING RESOURCES ON...

LEARNING AND TEACHING RESOURCES ON PRACTICAL FOR

CHEMISTRY AND COMBINED SCIENCE (CHEMISTRY PART) CURRICULA

Sophia SL Cheng

Science Education Section, EDB

Learning and Teaching Resources for Senior Secondary Chemistry

and Combined Science (Chemistry Part)

(http://cd1.edb.hkedcity.net/cd/science/chemistry/resources_by_topics/i

ndex.html)

INTEGRATE SBA WITH LEARNING AND TEACHING

Example 1

Pre-lab assignment +

Volumetric analysis using HCl(aq) and Na2CO3(aq)

Topic XV Analytical Chemistry

Students should learn Students should be able to

d. Instrumental analytical methods

basic principles and applications of

colorimetry

understand the basic principles deployed in

the instrumental analytical methods, viz.

colorimetry, IR spectroscopy and mass

spectrometry

construct a calibration curve by measuring

absorbance of standard solutions

determine the concentration of a solution

using a calibration curve

2016 HKDSE Paper II Q3(b)

Topic XV(d) Instrumental

analytical methods

Objective

• To determine the amount of copper in a brass sample

Chemical reactions

3Zn + 2NO3- + 8H+ 3Zn2+ + 2NO + 4H2O

3Cu + 2NO3- + 8H+ 3Cu2+ + 2NO + 4H2O

2NO + O2 2NO2

The determination of copper in brass

The determination of copper in brass

The determination of copper in brass

Relative absorbance = log10(V0 / Vs)

where V0 is the voltage reading with a cuvette containing deionized water

Vs is the voltage reading with a sample in the cuvette

Deionised water

0.1 mol dm-3 CuSO4(aq)

0.2 mol dm-3 CuSO4(aq)

0.3 mol dm-3 CuSO4(aq)

0.4 mol dm-3

CuSO4(aq) 0.5 mol dm-3 CuSO4(aq)

Sample solution

Voltage reading / V

0.822 0.794 0.766 0.736 0.705 0.649 0.735

Relative absorbance

log10(0.822/ 0.794) = 0.0151

0.0306 0.0480 0.0667 0.103 0.0486

The determination of copper in brass

Conc. of sample Cu2+(aq) = 0.281 M Mass of Cu in brass solution = 0.178 g

% by mass of Cu in brass sample = 59.3%

Topic VIII Chemical Reactions and Energy

Students should learn Students should be able to

b. Standard enthalpy changes of

reactions

explain and use the terms: enthalpy change

of reaction and standard conditions, with

particular reference to neutralisation,

formation and combustion

carry out experimental determination of

enthalpy changes using simple calorimetric

method

calculate enthalpy changes from

experimental results

2019 HKDSE Paper IB Q8

Topic VIII(b) Standard enthalpy

changes of reactions

Determining the Stoichiometry of Reaction Between ClO- and S2O32-/OH-

Objective

To determine the stoichiometry of a chemical reaction

_____ClO- + _____S2O32- + _____OH- _____Cl- +_____SO4

2- +_____H2O

Chemicals

Solution A: 0.5 M sodium hypochlorite, 55 mL

Solution B: 0.5 M sodium thiosulphate in 0.2 M sodium hydroxide, 55 mL

For every 1 mole of Na2S2O3 that reacts, 4 moles of NaClO are needed. 4 ClO- + S2O3

2- + 2 OH- 4 Cl- + 2 SO42- + H2O

Sample data

Volumetric Analysis: “Low Sodium” Salt Substitutes

◦ To determine the proportions of potassium

chloride and sodium chloride in low-sodium salt

substitutes using a titration procedure

◦ Mohr Method

NaCl(aq) + AgNO3(aq) NaNO3(aq) + AgCl(s)

KCl(aq) + AgNO3(aq) KNO3(aq) + AgCl(s)

◦ [End-Point Reaction]

2Ag+(aq) + CrO42-(aq) Ag2CrO4(s)

red ppt

At the beginning AgCl is being formed

during titration

Ag2CrO4(s) is formed at

the end point

Data analysis

From the titration results, the no. of moles of Cl-(aq) = 0.0149 mol

Mass of the salt sample = 1.00 g

Let mass of NaCl be x, then mass of KCl = 1.00 – x

No. of moles of Cl- from NaCl = x

58.5

No. of moles of Cl- from KCl = 1.00 − x

74.5

Total no. of moles of Cl- = x

58.5 +

1.00 − x74.5

= 0.0149

x = 0.403

Therefore, % of NaCl by mass = 40.3%

% of KCl by mass = 59.7%

Some more practical activities

Typical reactions of various functional groups (Topic XI c)

◦ Reduction of Vanillin with Sodium Borohydride

Rate of Reaction (Topic IX b)

◦ Reaction of Phenolphthalein in NaOH solution (with the

use of datalogger)

Microscopic World II (Topic VI b)

◦ Evaporation and Intermolecular Attractions

Analytical Chemistry (Topic XV b)

◦ Thin-layer Chromatography of Painkillers

http://www.hkeaa.edu.hk/tc/sba/sub_info_sba/dse_subject.html?7&4

Chemistry Experimental Techniques

YouTube Channel:

https://qrgo.page.link/sKAf4

http://minisite.proj.hkedcity.net/safetyonline/eng/index.html

References and resources for Chemistry, Science Education, EDB

(http://www.edb.gov.hk/en/curriculum-development/kla/science-

edu/ref-and-resources/chemistry.html)

Curriculum Documents, Science Education, EDB

(http://www.edb.gov.hk/en/curriculum-development/kla/science-

edu/curriculum-documents.html)

Course ID Course title Date & Time

CDI020200409 Understanding and Interpreting the

Chemistry and Combined Science

(Chemistry Part) Curricula (Re-run)

28/10/2019

2:00 p.m. – 5:00 p.m.

CDI020191377 Course for Laboratory Technicians:

Understanding and Interpreting the

Chemistry and Combined Science

(Chemistry Part) Curricula (New)

15/11/2019

2:30 p.m. – 4:30 p.m.

CDI020200460 Course for New Teachers – Promoting

the Quality of Chemistry Learning with

Effective Teaching Strategies and

Learning Activities (New)

29/11/2019

2:00 p.m. – 5:00 p.m.

Training programme (Oct/Nov 2019)

https://forms.gle/TZNxiP9hSjwKXng6A

Contact information

Sophia Cheng

Tel: 3698 3439

Email: sophiaslcheng@edb.gov.hk

Tim Tse

Tel: 3698 3438

Email: timbltse@edb.gov.hk