Q&A - P3 Science

[Laurenwkids]

tianzhu:

JayneLL:

could you let me know where you get these questions.

Hi

This question may be from Toanan Science SA2 2009.

Please go to page 7 of this link to see Q8.
http://www.orlesson.org/orp/09Sc/P4-09-Sc-SA2-TaoNan.pdf

Best wishes

Thanks Tianzhu for the link. I was :? when I saw the question.
Got to read up more to help my daughter.

[tianzhu]

peggy:

Can anyone help with this P4 qtn ?


John was running around the field during recess before his teacher brought the class into an air-conditioned room. He felt cold after he entered the room.

A) Explain why John felt cold in the air conditioned room.
B) There are air spaces in a woollen jacket.
When John put on his jacket, he felt warm. Explain how the jacket had kept John warm.

Hi

In this question, we are given a situation with John running around the field during recess. He was then brought to an air-conditioned classroom.

Therefore, it’s important to give answers that connect to the situation in the question.

Under the topic of heat in P4, students learned that heat always flows from a hotter to a colder place or object.

Some thoughts that may be helpful in answering this question.

(a)Exercising ----- higher body temperature ------ heat lost from body to cooler surroundings ----- John felt colder.

(b)Body warm the air near it ----- a layer of air is trapped by the woolen jacket ----- woolen jacket with air spaces ----- a poor conductor of heat -------reduce heat loss ----- keeps John warm

Best wishes

[tianzhu]

Laurenwkids:

Thanks Tianzhu for the link.

Hi

You're welcome.

Best wishes

[peggy]

Thanks Tianzhu. Very well explained.

[atutor2001]

peggy:

Can anyone help with this P4 qtn ?


John was running around the field during recess before his teacher brought the class into an air-conditioned room. He felt cold after he entered the room.

A) Explain why John felt cold in the air conditioned room.

The key point to note in this question is that he was running around before going into the air-con room, i.e. he is hot with perspiration.


In the air-con room, he will feel colder when he is hot & wet than if he is dry. The reason for feeling colder are :

1. The difference in his body temp and the surrounding temperature increases causing the body to lose heat faster.

(second reason - not in syllabus but sometimes tested)
2. The perspiration on his body evaporates faster in an air-con room because the humidity is lower (air-con remove water vapour in the air). Faster evaporation means heat is lost by the body to the sweat at a faster rate i.e. feeling colder.


In my opinion, the most kiasu answer will be :

Running causes his body temperature to increase while the air-conditioner causes the room temperature to decrease. Therefore, the difference in temperature between his body and the surrounding air increases causing his body to lose heat at a faster rate which is why he feels cold.

(the underlined words should be what the marker is looking for)

[tianzhu]

peggy:

Thanks Tianzhu. Very well explained.

Hi

You're welcome.

Best wishes

[peggy]

Many thanks to all who has responded to my qtn !

[elkniwt]

Hi,


I refer to Qn 10 in this paper,
http://www.orlesson.org/orp/09Sc/P4-09-Sc-SA2-HenryPark.pdf

For this type of question, is it necessary to draw the outlines of transparent objects for the shadows?

Regards

[tianzhu]

elkniwt:

Hi,


I refer to Qn 10 in this paper,
http://www.orlesson.org/orp/09Sc/P4-09-Sc-SA2-HenryPark.pdf

For this type of question, is it necessary to draw the outlines of transparent objects for the shadows?

Regards

Hi

The objects must be translucent or opaque to make a shadow. Translucent object will give a lighter shadow.

If you see from the position of a person holding the torch, option (1) is a logical answer.

Best wishes

[elkniwt]

Dear tianzhu,


Thank you for your quick reply. But may I know how come for the clear plastic which is transparent, it is necessary to draw the outline? My dd said teacher taught that transparents objects do not cast shadow.

Thanks for help. It is kind of confusing for me and the child cos for some papers, the outlines of transparent objects are not drawn, but for this qn the correct ans is the one with the outline drawn.

Regards.

tianzhu:

Hi

The objects must be translucent or opaque to make a shadow. Translucent object will give a lighter shadow.

If you see from the position of a person holding the torch, option (1) is a logical answer.

Best wishes