Q&A - PSLE Science

[tianzhu]

atutor2001:

Actually the \"apple question\" is still bothering me.

Hi atutor2001

Hope this article helps.
http://www.scholastic.ca/education/science_place/downloads/alive_tg_on.pdf

Have fun.

Best wishes

[atutor2001]

Hi tianzhu


Thanks

[Full.010894Cream]

an interesting article on leave disk indeed!!


BTW, what's the conclusion on the 'apple'? :?

[atutor2001]

Hi Full.Cream


Most of the articles indicated that picked apple is dead. Those that said that it is still alive concluded so because they had included the seeds as part of the apple. However, the definition of fruit (apple is a fruit) does not include the seeds as part of a fruit. (A fruit is the fleshy part that protects the seeds and helps in seed dispersal.)

When I tried to match the 7 characteristics of a living thing to a picked apple, most of the characteristics do not match. So I have accepted and concluded that a picked apple is DEAD

[Full.010894Cream]

atutor2001:

Hi tianzhu


A very interesting article indeed. Thank you.

However, an immediate question came to my mind - Why can a plucked leaf continue to carry out photosysnthsis?

My guess is that the cells of in a plucked leaf are \"alive\" for quite a number of days. That brings my thought to the term \"alive\". Is it right to say that the cells are \"alive\" or should it be \"functional\" or some other biological term. Thanks in advance.

Regards

What happens when a human dies? In the context of first aid, the cells start to die after abt 4mins due to the deprivation of oxygen (IIRC).

SO when we pluck the leaves from the plant, the cells in the leaves are still very much alive. Couple with the fact that it is submerged in water and also able to photosynthesize, it'll lose very little water and also produce oxygen to sustain live at the cell level. Therefore its state of 'aliveness' is prolonged. Acceptable reasoning?

[atutor2001]

Full.Cream:

What happens when a human dies? In the context of first aid, the cells start to die after abt 4mins due to the deprivation of oxygen (IIRC).

SO when we pluck the leaves from the plant, the cells in the leaves are still very much alive. Couple with the fact that it is submerged in water and also able to photosynthesize, it'll lose very little water and also produce oxygen to sustain live at the cell level. Therefore its state of 'aliveness' is prolonged. Acceptable reasoning?

Ya agreed.

Now I ask myself this question when deciding whether something is alive or dead - Is live processes (i.e. respiration, absorption of water, nutrient..., excretion, ..) still in progress? If yes then it is a living thing.

[Full.010894Cream]

well, I wld not consider a plucked leaf a living thing coz we shdn’t go to the celol level to determine what is a living thing.

[glchua]

For any plucked fruit, physiological processes are still happening. A banana still ripens, mangoes give off heat if you encase it. An apple is thus still living.


If a dismembered plant is immediately considered dead, then grafting is not possible as a farming technique.

This is also true of dismembered parts of an animal. The tissue is still alive.

The apple is considered dead when it starts to rot. Respiration ceases, defense ceases, and microbes take over.

Sorry, just my opinion.

[glchua]

tianzhu:

glchua:

Not true. Water needs a lot of heat to increase 1 degree of temperature. Compared with iron, it is about 10 times more! Energy required to pull the orderly molecules from a solid state to a messy and energetic liquid state is very high too.

Hi

Thank you for your view. I am trying to look at this question from the concepts on heat learned in P4.

What would our primary kids think when they first read this question? Formula such as Q =mass x specific heat x temperature difference, specific heat capacities of water and iron and latent heat of fusion are not taught yet.

In Q26, one has to compare the heat gained by the water from the hot iron as compared to the heat gained by the melting cube of ice, bearing in mind that the beaker of water has greater mass than the cube of ice.
Primary students learn that heat flows from a higher region to a lower region. Hence, in applying this principle, a bigger temperature difference, greater heat gain for the water in the beaker(option 2).

This is how I would have answered this question. Of course my answer may not be right.

Best wishes

I apologize if I offended. My calculations may not be right too, since these stuffs are learnt long ago and I don't use these knowledge in my current line of work, not frequently anyway.

The issue here is not the answer. The original question from the school is wrong. One can't assume that all students see things in the limited light of what the teacher had taught. So it boils down to learning for giving correct answers, or learning to get closer to the truth.

Students who knew a little bit more through parents, internet, reading, etc would give a wrong answer or would get confused. If answers require careful phrasing (as some previous post had suggested), then teachers should do so too.

[Full.010894Cream]

Need some help here.


CHIJ 2008
http://img697.imageshack.us/img697/5417/chij2008q1.jpg\">
Ans : (3)

I understand spider does not have feelers

http://img4.imageshack.us/img4/8606/chij2008q22.jpg\">
Ans : (2)

How come (D) is true?