Tuesday, February 19, 2019

Thursday, January 17, 2019

How do you prepare agar soaked with indicator?


How do you prepare agar soaked with indicator?





2 packs of agar white powder in 1 litre water, bring to a boil. 
add in Universal indicator (abt 3 drops)
pour into container/mould (any container will do)
put in fridge and let it set overnight






But only during cooling part, not during heating.  Your methyl orange might be flammable.  https://www.cdhfinechemical.com/images/product/msds/43_1892059653_MethylOrangeIndicatorSolution-MSDS.pdf

source: Joelle JurongWestSS

Wednesday, January 2, 2019

Links for EVG Science Teachers



Hi All,
Below are the links to sharing folder, Gdrive & blogspot :-




 

G+ drive

Sharing folder

Safety features, procedures & checklist for science teachers


 

REQUISITION FORM


 


SCIENCE LAB BOOKING LOCATION


 

Precaution in Science Experiment


 

GCE O Question Papers



Explosive Precursors Record


 

CHEMISTRY STOCKLIST


 

PHYSICS & STATIONERY STOCKLIST


 

bIOLOGY & MAINTENANCE STOCKLIST


 

SCIENCE PURCHASE


 

BREAKAGE LOAN ITEMS RESOURCES


 

SCIENCE LAB MGMT AND SAFETY HANDBOOK




Thursday, March 29, 2018

How to prepare thymolphthalein indicator?



👉How to prepare thymolphthalein indicator?
👉Thymolpthalein is to substitute use of phenolothalein indicator..
👉but normal VA still use methyl orange
👉It will be clear in acid and blue in alkaline. End pt will be clear. Very difficult to determine end point cos colour change is almost the same as in acid.
👉If end point is clear... doesn't it means that the solution is too acidic? 🤔 end point should be light blue right? I mean when phenolpthalein was still in use, end point was light pink
👉Juz to make sure... this is something new
👉Yes light blue. at least better than methyl orange... orange to reddish orange almost cannot tell


👆This morning really hard to see from red to orange
👉Must compare side by side then can see the difference😂
👉The red is too acidic 😂 should be closer to orange
👉Juz 1 drop only make a huge difference
👉Methyl orange is juz plain poor pH indicator. Can understand why MOE needed a better indicator 😂
👉Then without realising turn yellow😂
👉some teachers prefer screen methyl orange

👉where to store them?
👉Put in amber dropping bottle. Usually made fresh just for 2-3 classes.

👉How long can the indicator last?
👉Can last for a week

Friday, March 23, 2018

Tuesday, January 30, 2018

Tuesday, November 21, 2017

Understanding and Preventing Fire and Chemical Hazards in the Laboratory







 







 



Source: www.wshc.sg and
Source: Dr Wayne Lee Forday
School of Life Sciences and Chemical Technology
Ngee Ann Polytechnic

Thursday, May 5, 2016

Pictograms and Hazard Codes


PICTOGRAMS AND HAZARD CODES

Description
Pictogram
Hazard class and hazard category:
Exploding Bomb
GHS01
Unstable explosives
Explosives of Divisions 1.1, 1.2, 1.3, 1.4
Self reactive substances and mixtures, Types A,B
Organic peroxides, Types A,B

Flame
GHS02
Flammable gases, category 1
Flammable aerosols, categories 1,2
Flammable liquids, categories 1,2,3
Flammable solids, categories 1,2
Self-reactive substances and mixtures, Types B,C,D,E,F
Pyrophoric liquids, category 1
Pyrophoric solids, category 1
Self-heating substances and mixtures, categories 1,2
Substances and mixtures, which in contact with water,
emit flammable gases, categories 1,2,3
Organic peroxides, Types B,C,D,E,F

Flame Over Circle
GHS03
Oxidizing gases, category 1
Oxidizing liquids, categories 1,2,3

Gas Cylinder
GHS04
Gases under pressure:
- Compressed gases
- Liquefied gases
- Refrigerated liquefied gases
- Dissolved gases

Corrosion
GHS05
Corrosive to metals, category 1
Skin corrosion, categories 1A,1B,1C
Serious eye damage, category 1

Skull and Crossbones
GHS06
Acute toxicity (oral, dermal, inhalation), categories 1,2,3

Exclamation Mark
GHS07
Acute toxicity (oral, dermal, inhalation), category 4
Skin irritation, category 2
Eye irritation, category 2
Skin sensitisation, category 1
Specific Target Organ Toxicity – Single exposure, category 3

Health Hazard
GHS08
Respiratory sensitization, category 1
Germ cell mutagenicity, categories 1A,1B,2
Carcinogenicity, categories 1A,1B,2
Reproductive toxicity, categories 1A,1B,2
Specific Target Organ Toxicity – Single exposure, categories 1,2
Specific Target Organ Toxicity – Repeated exposure, categories 1,2
Aspiration Hazard, category 1

Environment
GHS09
Hazardous to the aquatic environment
- Acute hazard, category1
- Chronic hazard, categories 1,2
- Source from sigma aldrich for reference purposes

Wednesday, May 4, 2016

To investigate the Effect of Varying Temperature on the Rate of Respiration of Germinating Seeds


To investigate the Effect of Varying Temperature on the Rate of Respiration of Germinating Seeds

Description
Germinating seeds actively respire to produce energy for growth. The rate of respiration can be obtained by measuring the uptake of oxygen per unit time.

Apparatus & Materials needed :-

beaker 100ml 
beaker 600ml
conical flask 100ml
1 rubber bung fitted with a delivery tube
5g germinating seeds (supplied in petri dish)
1 packet of soda lime wrapped in muslin cloth
coloured water
thermometer
30cm ruler
electronic balance
graph paper
stopwatch           }
test tube holder   }    optional
dropper              }
water bath          }


soda lime


To prepare germinating seeds need 4days in advance before the experiment.


Day 1 : Soak green beans about 250 grams in 1 litre of water


Day 2 : Place cotton wools or towels onto trays. 
Remove green beans from beaker and transfer to trays.
Wet trays just covering the green beans.
Cover the trays with black plastic bags.


Day 3 : Seeds starts to germinate


Day 4 : Germinating seeds for the experiment

Alternatively can buy readily available Alfalfa Sprouts 
from supermarkets costly around $3.30 per 125g



Experimental set up


Procedure


  1. Weigh 5g of germinating seeds and place them in the conical flask.
  2. Tie the string to the packet of soda lime.
  3. Prepare water bath maintained at 30oC.
  4. Set up the apparatus as shown above.


Thursday, January 14, 2016

Monday, November 2, 2015

Thursday, February 26, 2015