Q&A - P3 Science

[tianzhu]

[quote]A few spoonfuls of salt were added into the beaker of crushed ice.Which one of the following graph correctly shows how the readings of thermometers p and W change when the salt was added?


Sorri, cant scan the graph cos no scanner.May i just write it down.

Answer : Temperature of p drop as mins go on,temperature of q, drop from zero to freezing point and go up but still below zeros degree.[/quote]
Hi
Where are the positions of thermometers P and W? What is temperature q?
Without scanner, you may try to take a picture of the question using a digital camera and insert as an image.

[tianzhu]

Lynn2:

Hello all, am trying to work out some MCQ with my gal, can cross check on ....


1 We can clearly feel our heartbeat at our....

ans : wrists,temples and neck.

May I know why temples is one of the point?

2 What will happen if we have a weak heart?

thanks

Hi
May I suggest you post the complete questions showing all options for these MCQ questions. Sometimes. we can use elimination process to weed out options that are obviously offside.

[Lynn2]

Hi Tianzhu


Thanks

Here is the full question.

We can clearly feel our heartbeat at our____
a wrists b temples
c neck d forehead

1 a and c 2 b and d only
3 a b and c only 4 a,b,c and d

tianzhu:

Lynn2:

Hello all, am trying to work out some MCQ with my gal, can cross check on ....

1 We can clearly feel our heartbeat at our....

ans : wrists,temples and neck.

May I know why temples is one of the point?

2 What will happen if we have a weak heart?

thanks

Hi
May I suggest you post the complete questions showing all options for these MCQ questions. Sometimes. we can use elimination process to weed out options that are obviously offside.

[Lynn2]

Thanks for the great suggestions.I will use my digital cam take the questions and post up later


cheers

tianzhu:

[quote]A few spoonfuls of salt were added into the beaker of crushed ice.Which one of the following graph correctly shows how the readings of thermometers p and W change when the salt was added?

Sorri, cant scan the graph cos no scanner.May i just write it down.

Answer : Temperature of p drop as mins go on,temperature of q, drop from zero to freezing point and go up but still below zeros degree.

Hi
Where are the positions of thermometers P and W? What is temperature q?
Without scanner, you may try to take a picture of the question using a digital camera and insert as an image.[/quote]

[Lynn2]

Hi Tianzhu


Finally able to play with the gadget and here is the questions as below:

tianzhu:

[quote]A few spoonfuls of salt were added into the beaker of crushed ice.Which one of the following graph correctly shows how the readings of thermometers p and W change when the salt was added?

Sorri, cant scan the graph cos no scanner.May i just write it down.

Answer : Temperature of p drop as mins go on,temperature of q, drop from zero to freezing point and go up but still below zeros degree.

Hi
Where are the positions of thermometers P and W? What is temperature q?
Without scanner, you may try to take a picture of the question using a digital camera and insert as an image.[/quote]http://www.postimage.org/image.php?v=aV1Sz9L9

[tianzhu]

Hi


I think there are two ways to take heart rates.

1)place your hand on the pulse of your wrist
2)place your fingers on the side of the Adam’s apple on your neck until you find the pulse.

You may refer to this site for my information.
http://www.nemahealth.org/programs/healthcare/heart_rate_pulse.htm#2

A good site to find out more about our heart.
http://www.myheart.org.sg/?page_id=38

I suggest that you check with the science teacher for the correct answer.

[Tang]

http://www.postimage.org/image.php?v=aV1Sz9L9


Answer is (3).


When salt is added into the crushed ice, the temperature (Q) will drop below 0 degree C.

The water in the test tube will lose heat and freeze into ice. So temperature (P) will drop to 0 degree C.

Over time, to keep the ice in the test tube frozen, the temperature (Q) of the crushed ice rises while ice remains at 0 degree C (P).

[Tang]

http://test-paper.info/filemgmt/viewcat.php?cid=85


P4 Science SA2 S008 Tao Nan Question 34.

Q34a) Use the appropriate letter (A to J) from the diagram above. Write down the correct order, the internal organs involved in the digestion of food.

Worksheet answer B, C, D, H

B - Mouth
C - Gullet
D - Stomach
H - Small intestine.

Query - Should C (gullet) be included as part of the internal organs involved in the digestion of food ?

Thanks.

[Full.010894Cream]

Tang:

http://www.postimage.org/image.php?v=aV1Sz9L9


Answer is (3).


When salt is added into the crushed ice, the temperature (Q) will drop below 0 degree C.

The water in the test tube will lose heat and freeze into ice. So temperature (P) will drop to 0 degree C.

Over time, to keep the ice in the test tube frozen, the temperature (Q) of the crushed ice rises while ice remains at 0 degree C (P).

when salt is added to the ice, the melting point of the ice is lowered, ie, it goes below 0 deg C.

That being said, I believe the ice/salt mixture will turn into water faster but I don;t think the temp will go down.

In order for the temp to go down, heat must be removed from the mixture. But from the pic, heat seems to be added to the ice since the water in the test tube gets colder.

Did I go wrong somewhere?

[atutor2001]

Full.Cream:

when salt is added to the ice, the melting point of the ice is lowered, ie, it goes below 0 deg C.

That being said, I believe the ice/salt mixture will turn into water faster but I don;t think the temp will go down.

In order for the temp to go down, heat must be removed from the mixture. But from the pic, heat seems to be added to the ice since the water in the test tube gets colder.

Did I go wrong somewhere?

This is a question that is beyond primary level which I don't understand why schools have included in their paper - maybe trying to impress.

The \"layman\" explanation is as follows :

1. When salt is added, the Freezing point of those parts of the ice that are in contact with the salt will be lowered. So, those portions of the ice cannot remain as solid and \"must melt\".

2. In order for ice to change to liquid, heat must be gained (latent heat). Interestingly, those parts of the ice in contact with the salt, instead of gaining heat from external sources, somehow are able to draw on its \"own heat\" to change from solid to liquid phase.

3. Having used its own heat to melt and become salt solution, its temperature will decrease - becoming negative. Therefore, the melted solution will be less than zero degree (can be as low as -14 degree C if I remember correctly).

Sorry if I confuse you. But the explanation using science terms is even more confusing.