Q&A - PSLE Science

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Q&A - PSLE Science

Postby tianzhu » Fri Jan 02, 2009 6:00 pm

Moderator's Note: Please use this thread to ask for help on specific questions. Please refrain from out of topic chatter in this thread to make it easier for the community to find the answers they need.

Original Title: Upper Primary Science

Respiratory Systems

Under respiratory systems, there are two popular types of questions concerning the increase in breathing rates and heartbeat while doing exercises. What is the most appropriate information to put in while answering these types of questions?

Q1) After playing basketball with his friends, Tom checked his breathing rate again. He found that his breathing rate was 20 breaths per minute. Why was his breathing rate higher?

Q2) Jerry ran around the track for 20 minutes.
(a) What would happen to his heartbeat after 20 minutes? (b)Why is this so?

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Postby tianzhu » Fri Jan 02, 2009 6:38 pm

Chestnuts roasting on an open fire

Many love roasted chestnuts. While passing around stalls in the heartlands, the fragrant smell is simply tempting. Each merchant would stir their wok constantly, mixing chestnuts with tiny pebbles.

While waiting for these chestnuts to be cooked to perfection, spare some thoughts on why we need to roast chestnuts with tiny pebbles? Why can’t we cook chestnuts in a wok without tiny pebbles?

Please help to explain using information within Primary Science syllabus.

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Postby caroline3sg » Fri Jan 02, 2009 10:50 pm

Tianzhu
The chestnut question came out in 2008 PSLE Science.

The answer someone mentioned is "the frying of chestnut in small rocks/sand/pebbles is to ensure larger surface are in contact with the chestnut in order for more heat to be conducted to the chestnut to cook it faster.

Your question asked in negative sense, so has to revert the above answer to negative --> if fry/cook without pebbles, the chestnuts would take a much longer time to be roasted because the shape is not flat but rounded on one side.

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Postby caroline3sg » Fri Jan 02, 2009 10:52 pm

For respiratory system, complete answer can be found in P5. P4 only partial answer. Your child in P4?

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Postby tianzhu » Sat Jan 03, 2009 6:09 am

Hi caroline3sg

In answering open ended question, students are expected to use multiple process skills and apply the relevant concepts. You need to know how much details to put in. Giving unnecessary details wastes precious time, while writing too little causes you to lose precious marks.

Under examination conditions, our young ones have to learn to cook the right portion using the right ingredients, so to speak.

My child is in P6.I am trying to gather some inputs so that,maybe, relevant information from interested members can be pooled together to get the most appropriate answer. Many heads are always better than one.

Answers in the form of what a student is expected to put in an examination will be very much appreciated.I hope that this thread can gain momentum and arouse the interest of parents/students to participate actively.

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Postby caroline3sg » Sat Jan 03, 2009 8:18 am

tianzhu
my child also P6.

OE questions, even 2 marks, have to write a lot. To LINK KEY WORDS, CONCEPTS & APPLICATIONS. There should be sufficient time to complete Science paper as compared to Maths.

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Re: Upper Primary Science

Postby ChiefKiasu » Sat Jan 03, 2009 8:46 am

tianzhu wrote:Respiratory Systems...
Q1) After playing basketball with his friends, Tom checked his breathing rate again. He found that his breathing rate was 20 breaths per minute. Why was his breathing rate higher?...


I don't know the actual syllabus and scope yet, but here are some things I observed:

Q1) Ventilation rate 20 breaths per minute after exercise is quite low. That is almost when a person is sitting down, relaxed. Average should be between 35 to 70 for exercising. However this is controlled by the depth of breathing too. Deeper breathing allows more oxygen to be available to the lungs.
Key points:
- Blood contains oxygen which is used by cells to produce energy in our muscles
- Oxygen cannot be stored for more than a few minutes, so our lungs must work continuously to replenish the oxygen in our blood.
- During exercise, our cells burn energy faster to produce more energy for the body. This creates more carbon dioxide as a waste product. Our brain detects this increase in CO2 and triggers our lungs to ventilate faster and deeper to collect more oxygen for our body.

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Postby caroline3sg » Sat Jan 03, 2009 4:18 pm

chiefks
I am not expert, but your ans is almost there. missing keywords: circulatory system, heart because both systems work together.

Also, need to explain why need to get rid of carbon dioxide.

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Postby tianzhu » Sat Jan 03, 2009 4:51 pm

Electricity

Q1) Joe decided to make a bulb light up brighter. What should he do?

Q2) Using the same number of batteries, does arranging two bulbs in parallel cause the bulbs to be brighter as compared to arranging the two bulbs in series?

Q3) For bulbs arranged in parallel, does it require more batteries for them to shine as brightly as compared to bulbs arranged in series?

Q4) Do batteries arranged in parallel have a longer life span as compared to those arranged in series?

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Postby ChiefKiasu » Sat Jan 03, 2009 6:29 pm

tianzhu wrote:Electricity

Q1) Joe decided to make a bulb light up brighter. What should he do?

Q2) Using the same number of batteries, does arranging two bulbs in parallel cause the bulbs to be brighter as compared to arranging the two bulbs in series?

Q3) For bulbs arranged in parallel, does it require more batteries for them to shine as brightly as compared to bulbs arranged in series?

Q4) Do batteries arranged in parallel have a longer life span as compared to those arranged in series?


A1) Increase the voltage by connecting the batteries in series.

A2) Connecting batteries in series will cause the voltage to be greater than batteries in parallel by a number of times equal to the total number of batteries.

A3) It does not matter how many batteries are placed in parallel - the voltage remains the same even if the number of batteries are more than those in series.

A4) Batteries arranged in parallel will have a longer life span by a number of times equal to the total number of batteries compared to those arranged in series.

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