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Monthly Archives: July 2012

Student has maths test the next day. My husband helped to video my explanation and posted it online so she can see.

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Jessie, its for you. 🙂

I hope this video cleared some of your doubts and you can “kill” the simultaneous equations questions tomorrow. 🙂

This is my first time doing something like this. I apologise for the poor lighting, loud volume as it was an impromptu video to explain to you before your test tomorrow. And i was without make-up. Gosh!! Hehe.

Thank God the camera is not in high resolution.

Think some portions of the video are quite shaky and some portions, i speak in bad grammer. Ooops. Hee. Also, the camera was very near and hence one can hear me speaking quite loudly and the pitch captured is slightly high. Hehe.

Apart from all these drama, i hope you saw my passion for mathematics and understood  the mathematics concept for solving simultaneous equations.. 🙂

(Click below for the video presentation)

Have fun in your mathematics test tomorrow! 🙂

Feel like sharing some notes on Electricity

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Electricity


Was browsing through my tuition notes folder and felt like sharing some physics notes.

I have read a lot of guidebooks with detail notes. In fact, there are a lot of pretty good ones. However, it takes a disciplined child to read them thoroughly and digest them.
Also, one of my student asked me “Wah teacher, so many points even in the guidebook, how to memorise ALL?”

Most of my students do not fancy their textbook materials as there are a lot of details.

Teaching some students on electricity now. So i compiled a few key points on this topic.
· V=IR (Main formula in this chapter)

· Identifying Series and parallel circuit

(If you do not know how to differentiate a series and parallel circuits, please PM me.)

Series Circuit

· Ammeter must always connected in series to show reading if not ZERO.

· Rtotal = R1+R2 (series)

· For series, everywhere you put the ammeter, current is the same ( NOT FOR PARALLEL).

Parallel Circuit

· 1/Rt = 1/R1+ 1/R2, It = I1+I2

· In parallel circuit, the more bulbs or resistors, R decrease, I increase.

Circuit symbols – Be familiar with these symbols

Resistance

· Nichrome has higher R than Cu.

More heating effect.  I decreases, less bright if nichrome is used.

Resistance depends on

(a) length of conductor

(b) cross-sectional area of conductor

(c) temp of conductor

(d) type of conductor ( Please note that silver has better conductivity than copper and gold. But it is seldom used as conductors/wires because it oxidise easily. Although gold has a lower conductivity than copper, it is used extensively in semiconductor chips because its reactivity is very low.)

Short circuit

A short circuit is an abnormal connection between two nodes of an electric circuit intended to be at different voltages. (Wikipedia)

This results in an excessive current, causing overheating, circuit damage, fire and maybe explosion.

***A common type of short circuit occurs when the positive and negative terminals of a battery are connected with a low-resistance conductor, like a wire. ***

***Often comes out in tests and exams***

Calculating Electrical Power

Electrical power(W) = Energy converted (J)/Time (s)

Electrical energy used = electrical power (kW) * Time (hr)

Cost = Electrical energy used (kWh) * Electricity rate

Woo hoo! Another testimony !!

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I received this image via watsapp yesterday. I am so happy for this girl and there was a sense of achievement all over me.

By the way, I only taught her Mathematics and Science. She did well in both.  🙂

She did well in her Home economics and English too. I believe its the positive attitude in her that leads to the manifestation of good grades. Besides good grades, I am very happy that she enjoys school, her cca, other school activities and has a lot of friends. *Reminds me of my secondary school days.**

I got her permission to post it in my blog.

Well done! Keep it up!

Lower Secondary Kinematics

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Although Kinematics is not exactly in the syllabus of lower secondary science, i realise that many schools has brought it down from upper secondary syllabus, teaching it in secondary 2. I believe this is to give students for time for O’Levels  revision in their final year. 🙂

Because Kinematics is not in lower secondary syllabus, questions on this topic can not be found in lower secondary assessment books.

Here are some of the questions i have come up with. (Aftering looking through some notes from different schools).

Jasmine & Jessie, i will be going through these questions with you two this week. 🙂

Kinematics

  1. Say what is acceleration to you ( Only proper English with science keywords will be accepted) 🙂

______________________________________________________________________________________________________________________________________________________

2.    Write down the formulas for this chapter

3.   Dodo is going to buy stationary. He walked a distance of 2.5km at an average speed of 4km/h. He then feels pain in his stomach and wants to go to the nearest toilet. He run for a further 20 minutes with an average speed of 10km/h to reach the nearest toilet. What was the average speed of the whole journey?

4.   An ambulance accelerates at a rate of 7.5m/s from rest for 15s. What is its speed at the end of 10s?

5.   Brandon runs at a speed of 120km/h at the start of the race. He then accelerates uniformly at 3m/s2 for 15s.  Calculate the final speed of Brandon.

6.  Cindy is travelling at 35m/s when she suddenly sees an obstacle in the middle of the road ahead about 200m. Oops. Of course, any driver will try to avoid the obstacle, not crash onto it. Let’s see if Cindy is able to avoid the collision. Cindy’s reaction time is 0.7s (Remember during this interval, her speed is 35m/s). After the brakes were applied, the bus travelled a further 120m in 10s before stopping.

a.)Calculate the distance travelled during Cindy’s reaction time.

b.) Calculate the deceleration of Cindy

c.) Calculate the average speed of Cindy from the time she see obstacle to the time the car stopped.

d.) Did Cindy avoid the collision? Explain.

7.  Baba drives at an initial speed of 15m/s for 5s and then accelerates uniformly to 23m/s in 10s. He drives at his speed for another 7s. Finally, he decelerates uniformly in 17s before coming to a rest.

a) Draw a speed-time graph for the description of motion above.

b) Calculate the acceleration in the 10s.

c) Calculate the deceleration in the 17s.

d) Calculate the total distance moved and the average speed for Baba’s whole journey.

8. In a bumper car ring, a car is knocked and it accelerated. The car move a distance of 1.4m in 1.1s.

a) Calculate the average speed of this knocked car.

b) If the acceleration of this car is constant, calculate its speed after 1.1s

c) Calculate the acceleration of this knocked car.

Another milestone. Badge recognition for students.

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My husband asked me if i also participated in Singapore Science Centre “Are you a young Scientist?” program in primary school.

I certainly did as i love Science. And i managed to collect a lot of badges too.

I AM A YOUNG BOTANIST

 

I AM A YOUNG ZOOLOGIST

 

My husband was crazy about those badges too and our discussion brought back fond memories and prompted me to do something for my students.

I usually give tests to my students randomly, especially after teaching them a new topic to ascertain their understanding.

Woke up early this morning and did this for one of my girl.

Hope this ‘badge’ motivate her as much as the young scientist badges did for me. 🙂

I believe there will be revised versions of badges along my tuition journey. I want to document this down. One day i shall look back at this original version and see how far i have progressed..   🙂

U got to know how to write chemical equations before you can balance them, right?

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Hey folks, you are not going to get nice equations written for you to balance all the time. 😉

So before you can show your superb chemical reaction balancing skills, you got to know how to write chemical equations first. And you needs to be familiar with the chemical formulaes at the every least.

Common ions are sulfate, nitrate, ammonium, carbonate, prosphate. Kindly PM me if you are still ensure on these ions formulaes. 🙂

Classifying Chemical Reactions

Most chemical reactions can be classified as one of these six basic reaction types:

· Synthesis (combination)

· Decomposition

· Single Replacement (oxidation-reduction)

· Double Replacement (precipitation)

· Acid-Base (neutralization)

· Combustion

1. Synthesis Reaction: A + B –> AB

Sodium (s) + chlorine (g) –> sodium chloride (s)

 

2. Decomposition Reaction: AB –> A + B

sodium bicarbonate (s) –> carbon dioxide (g) + sodium carbonate (s) + water (l)

 

3. Single Replacement Reactions: AB + C –> A + CB

hydrochloric acid, HCl (aq) + magnesium (s) –> magnesium chloride (aq) + hydrogen (g)

 

4. Double Replacement Reactions: AB + CD –> AD + CB

calcium chloride (aq) + ammonium hydroxide (aq) –> calcium hydroxide (s) + ammonium chloride(aq)

 

5. Acid-Base Reactions: HA + BOH –> BA + H2O

Sulfuric Acid, H2SO4 (aq) + potassium hydroxide (aq) –> potassium sulfate (aq) + water (l)

 

6. Combustion Reactions: Fuel + O2(g) –> CO2(g) + H20(g)

Hexane, C6H14 (l) + oxygen (g) –> carbon dioxide (g) + water (g)

Adapted from : http://www.arps.org/users/hs/thompsom/honors/unit_02/Balancing_Equations_Packet.pdf

Finally, here are some practice for you. ( from your favourite, beautiful and wise tutor. 🙂

First write the products of chemical reactions and write word equations as formula equations and balance correctly.

  1. Magnesium + hydrochloric acid →

2.   Nitric acid + sodium hydroxide →

3.   Silver nitrate reacts with copper to form copper (II) nitrate and silver.

4.   Chlorine gas react with potassium iodide

5.    Sulphuric acid +  gold carbonate →

That’s all, folks.

You are dismissed. 🙂

Elements Compounds, Mixtures, Atoms, Molecules

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I compiled some questions from assessment books and a few good schools in Singapore.

Here are some of “warm-up” questions on this topic.

As usual, those students who receive my mobile msg to attempt this week’s questions,

here you go! 🙂

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1) A student wrote “Bronze is a compound.”

Explain why this statement is incorrect. [Anglo-Chinese School]

2)Iron sulphide is formed from iron and sulphur. Which of the following statements about iron sulphide is true? [Anglo-Chinese School]

A)Heat energy is required to cause the formation of iron sulphide

B)Iron sulphide has similar properties as iron

C)Iron sulphide is the result of a change in state of iron and sulphur

D)The ratio of iron to sulphur is not fixed in a sample of iron sulphide.

3) Which 2 of the following boxes consist of only 1 element?

[St Margaret Secondary School]

A)I and II

B)I and III

C)II and III

D)II and IV

4) Which of the following has the same number of atoms as Ca(OH)2?

[St Margaret Secondary School]

A)AlCl3

B)BaSO3

C)K2CO3

D)PbSO4

5) Given that the electronic configuration of nitrogen atom is 2,5.

Which of the following statements is true for the ion of nitrogen?

[St Margaret Secondary School]

Number   of Protons Number   of electrons
A 7 7
B 7 10
C 10 7
D 10 10

6) How many different elements are there in ammonium carbonate (NH4)2CO3? [Temasek Secondary School]

A)2

B)3

C)4

D)5

7) [Preston Assessment book]

a)  Classify the following substances into elements, mixtures and compounds: ice, brass, silicon, salt, ink, starch solution, plastic, potassium, protein, glass, carbon, air.

b) Explain why sugar solution is a mixture while sugar is a compound.

8)Please write the formula and names of elements of the compound below. [Anglo-Chinese School]

Compound Formula   of compound Names   of elements found in compound
Nitric   acid
Common   Salt