Q&A - PSLE Science

[James Ang]

I had been getting my students to eat \"fried ice cream\" prior to the prelims exams and guess what, the \"fried ice cream\" question appeared in both Red Swastika and Poi Ching's prelims exams. My students get these questions correct, while other students do not believe ice cream can be \"fried\". This \"fried ice cream\" question is also found in Sec 4 Longman Physics Guide which explains that the ice cream does not melt in the hot oil because the ice cream is covered by a layer of flour dough with air bubbles which prevents the heat from being conducted to melt the ice cream inside because air is a poor conductor of heat.


Another question that came out in both Red Swastika and Gongshang prelims is that of the angler fish which lives in the abyss bottom of the ocean. The angler fish has a light on top of its head and guess what is the purpose of the light on top of its head in the dark surroundings under the ocean.

[tianzhu]

Thank you for your help.


The gills of a fish are covered by a very thin membrane. Why is it necessary for the fish to have such a thin membrane over the gills?

[atutor2001]

James Ang:

Another question that came out in both Red Swastika and Gongshang prelims is that of the angler fish which lives in the abyss bottom of the ocean. The angler fish has a light on top of its head and guess what is the purpose of the light on top of its head in the dark surroundings under the ocean.

Is it to attract preys?

[atutor2001]

tianzhu:

Thank you for your help.


The gills of a fish are covered by a very thin membrane. Why is it necessary for the fish to have such a thin membrane over the gills?

Is it to filter away any dirts/particles before the water enters the gils?

[tianzhu]

atutor2001:

Is it to filter away any dirts/particles

Hi
Sorry,I don't know the answer.I am still searching for a logical one.

Best wishes

[kelly1]

This is referring to the question about how the stem of a flower is slit in half, then dipped in coloured water on each side. The correct solution says that the xylem tubes in each half will take on the respective colour of the water where that half is dipped. My question is, can the stem also absorb water? The roots have been cut off in this diagram.

[atutor2001]

kelly1:

This is referring to the question about how the stem of a flower is slit in half, then dipped in coloured water on each side. The correct solution says that the xylem tubes in each half will take on the respective colour of the water where that half is dipped. My question is, can the stem also absorb water? The roots have been cut off in this diagram.

Yes, there is a special mechanism in the xylem that enables the water to flow upwards. Sugar cane (a stem) left standing with its cut end resting on dirty wet floor in hawker centre will absorb the dirty water and caused food poisoning. It happened locally before.

[atutor2001]

atutor2001:

tianzhu:

Thank you for your help.


The gills of a fish are covered by a very thin membrane. Why is it necessary for the fish to have such a thin membrane over the gills?

Is it to filter away any dirts/particles before the water enters the gils?

I google and got the answer that :

\"There are many small blood vessels in the gills and the these vessels are covered by thin membrane which absorbs oxygen from the water and carbon dioxide is expelled.\"

Will they set such difficult question in primary school?

[James Ang]

atutor2001:

I google and got the answer that :


\"There are many small blood vessels in the gills and the these vessels are covered by thin membrane which absorbs oxygen from the water and carbon dioxide is expelled.\"

Will they set such difficult question in primary school?

I believe that the membrane is a semi-permeable membrane quite like the cell membrane students learnt in P5 Science on cells, so the function of the membrane is to control the types of substances that enters and leaves the gills and usually the exchange of gases takes place in the gills, so it is right to say that oxygen is absorbed and carbon dioxide is removed in the gills due to the semi permeable membrane.

[James Ang]

atutor2001:

James Ang:

Another question that came out in both Red Swastika and Gongshang prelims is that of the angler fish which lives in the abyss bottom of the ocean. The angler fish has a light on top of its head and guess what is the purpose of the light on top of its head in the dark surroundings under the ocean.

Is it to attract preys?

yes you are right. Many students say it helps the fish to see in the dark, but it is actually a structural adaptation to attract preys.