Science Practical Olvl

Darkness_hacker99 SG

-___-" like that also can? Surprised Laughing

abyone SG

To be honest, I felt that the concentration they told us to do was too little... I realised from all my friends and their friends who took the Practical Exam had around the same results. It's either they have no reaction with Nitric Acid, or limewater only turned slightly chalky...

For me, I left Carbon Dioxide Gas present, Effervescence shown, bubbles appear, Test with limewater as my answers.

However, I also left Chlorine present for the next question.

In the end, I left my salt as Zinc Chloride.

So does that mean I'll would most likely get 3-5 marks deducted?

Do you guys feel that the standard will be down? As in, 21/30 = Sure A2? or B3? I really hope >21 = A2 & A1 ^^

Good Luck to all!!! Jia you for the Written exams!

Darkness_hacker99 SG

21 is about most likely a B3 grade.

TrixCereals SG

Actually seems slightly challenging imo.

P1 - 30/40
P2 - 45/65
P3 - 45/65
P5 - 20/30

Overall - A2

Darkness_hacker99 SG

After O level moderation, it'll be B3 or B4.

Scania N113CRB luver SG

Yes . Zinc Carbonate . Laughing I tested positive for carbon dioxide . I doubt Zinc Chloride produces carbon dioxide.

But i stupid go put Aluminium . Mad

Darkness_hacker99 SG

Very Happy

Y_Shun SG

wakao, you all still have the time to calculate how many marks u have _

Darkness_hacker99 SG

I think it's a rough estimation.

TrixCereals SG

Shocked Sounds scary. Hope the paper wouldn't be too easy though. Confused

^tamago^ SG

got what. every batch sure got some ppl do that. sometimes we discuss discuss will also come to some conclusion about how many marks we can get, even if we can't do much about it liao. Laughing Embarassed

TrixCereals SG

I morning mug until just now. Super tired but worry until cannot sleep. Sad

Arghhhhh.

TrixCereals SG

x2 Laughing

zannstar SG

the salt is zinc carbonate...

the salt is not a chloride, no chloride anion...

for the gas test, effervescence was observed...gas evolved produced a white precipitate in limewater...hence the gas is carbon dioxide.

Smile Smile Smile

felirox SG

why issit like that? Confused

ultranova3 SG

Do you smell the gas? Chlorine has a distinctive pungent smell. I seriously doubt any reaction will give Chlorine gas.
Reactions that give chlorine gas usually involve concentration HCl any concentrated reagents OR Organic reagents.
Adding dilute nitric acid to a sample will not give any Chlorine gas.
So the sample is definitely carbonate.
Just remember, to get chlorine gas is never easy. If chlorine gas is produced in like effervescent state, you have to do it in fume board.
19,000mg·min/m3 is lethal dose to 50 percent of exposed adults. If everyone gets chlorine effervescent, all the students inside the lab might have died. Laughing

Darkness_hacker99 SG

The normal grades without moderation is this(shown below):

As you can see, in order to achieve A1 without moderation, it'll require 75% marks. If for a particular year, the many students did very well for the paper, then quite a lot of students scoring A1 and this could be due to many reasons. One of it could be the paper is too easy, so moderation is a way to filter and accurately grade the better students with the weaker ones.

This is what the happened after moderation. A crude but realistic example: In order to obtain A1, you need to score at 84% of the marks.

As you can see from the graph because the A1 bench is push up, there will be lesser students scoring A1. This will preserve the integrity and the quality of students from that particular batch.

Similarly.. If the paper is too hard and very few people scored A1, the authorities may lower the boundaries so that a reasonable amount of student still can get A1.

Clear? Very Happy

Darkness_hacker99 SG

In school, we are too used to the A1 -75% etc bench mark. It is in fact a killer mentality to think this way.

In an actual national exam, chances of getting A1 with 75% is too low or not possible. You might need at least an 85% to get A1 after moderation!

felirox SG

That's cruel... Sad

Darkness_hacker99 SG

I am a victim of A1-75% mentality victim. Sad

Don't be like me ok? Buck up Wink

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