[admin]

A-Level Biology Tuition Singapore/H2 Biology Tuition/JC Biology Tutor

TOPIC 3: GENETICS OF VIRUSES AND BACTERIA – Part 2

LEARNING OUTCOME

(b)Describe the structural components of viruses.

ESSAY ANSWER

Main structural components of viruses:

Core – the genetic material, either DNA or RNA. (i.e. single-stranded OR
double-stranded)

Capsid – a protective coat of protein surrounding the core.
Capsids can come in many forms (helical (tobacco mosaic virus),
icosahedral (adenoviruses) and complex (bacteriophage T4).

Capsomeres – capsids are often built up through self-assembly of identical
repeating subunits

Nucleocapsid –core and capsid.

Envelope –additional lipoprotein layer around the capsid derived from the cell
surface membrane of the host cell.

For exam based questions and solutions, please contact Hp @9863 9633

[admin]

A-Level Physics Tuition Singapore/H2 Physics Tuition/JC Physics Tutor

Topic 1: Measurement Part 2

Distinguish between precision and accuracy.

Accuracy

Small systematic errors mean good accuracy.

A set of accurate readings is one where the readings are close to the actual value.

Precision

Small random errors mean good precision.

A set of precise readings is one that has a small spread or scatter of readings.

Please contact Angie @ 96790479 or Mr Ong @ 98639633 if you need help in Physics

[admin]

A-Level Economics Tuition Singapore/H2/H1 Economics Tuition

Test on Scarcity, Choice and Opportunity Cost
Notes on Demand, Supply and Price Mechanism

Section 1: Definitions (Improves ability to write introduction for essay questions)

a) Define scarcity
Scarcity arises because of __________ __________ and __________ wants. ___________ are ___________ because the world has a finite amount of them. __________ wants refer to the desire for ever higher levels of ____________ once a particular level of demand is met

b) Define choice
Choice refers to the act of _________ among ____________ and it involves sacrifices known as _________________ ____________. In making choices, the four most fundamental problems an economy must resolve are:

i. _________ to produce
ii. __________ ____________ to produce
iii. __________ to produce
iv. ________ _________ to produce

c) Production possibility curve is a curve which shows all the possible _____________ of two goods that a country can produce within a specified period of time with all its resources fully and __________ employed and at a given state of __________.

d) Define opportunity cost
Opportunity cost of any action refers to the next best ___________ foregone. It represents the real cost of that activity

e) A movement onto a PPC is due to an economy recovering from a ____________

f) An outward shift of PPC away from the origin is due to any of these:
i. Improvement in _________ of ____________
ii. Increase in ___________ of __________
iii. Improvement in ______________ of _____________
iv. Free __________ according to comparative advantage.

Please contact Angie Hp 96790479 or Mr Ong 98639633 if you need help in Economics and complete Notes and Test questions.

[admin]

A-Level Mathematics Tuition Singapore/JC Maths/H2 Math Tuition and Tutor

Revision Notes on Recurrence Relation

1. A recurrence relation is an equation that relates the general term of a sequence to one or more of its preceding terms.

For example,

xn+1 = 7 + xn , x1 = 0 ,

un = un−1 + 2 , u1 =1 , and

Fn+2 = Fn + Fn+1 , F1 = F2 =1 are recurrence relations.

These equations have the common property that if one term of the sequence is known, then we can find the next term by recursive substitution of terms. In this way, we can obtain the entire sequence of numbers. The subscript n
gives the position of the terms of the sequence; eg x1 is the first term and x2 the second term etc.

The general term n x of the sequence can take any real value; eg x1 = 0 , x2 =1 and x2 = −0.5 etc.

2. We say that a sequence of numbers xn converges to the limit l if xn ®l as n®¥ where l is a finite number. If no such number l exists, then we say that the sequence diverges.

3. A sequence is said to be increasing if the terms are increasing. Mathematically, this means xn+1 > xn for all n = 1, 2, 3, ….

The general approach in proving that a sequence is increasing is thus to show that xn+1 − xn > 0 for all n = 1, 2, 3, ….

4. A sequence is said to be decreasing if the terms are decreasing. Mathematically, this means xn+1 < xn for all n = 1, 2, 3, …. The general approach in proving that a sequence is decreasing is thus to show that xn+1 − xn < 0 for all n = 1, 2, 3, …. 5. A sequence is said to be constant if all the terms have the same value. Mathematically, this means xn+1 = xn for all n = 1, 2, 3, … Please contact Angie @96790479 or Mr Ong @98639633 if you need help in Mathematics

[admin]

O-Level Singapore/O-Level Combine Chemistry and Physics Tuition/Physics Tutor

Chapter 2 Kinematics Part 2

Exam Tip 4
Uniform acceleration means uniform increasing speed, i.e. the change of velocity (or speed) is a constant.

Exam Tip 5
Students should be able to describe the different kinds of motion of an object by reading distance-time or speed-time graph. They should be able to describe the change in distance, speed and acceleration

Exam Tip 6
Apply area formula for triangle, rectangle or trapezium according to the graph to find the distance travelled under the Velocity-Time graph

If you need help in the above topics, please contact Angie @96790479 or Mr Ong @98639633

[admin]

O-Level Singapore/O-Level Combine Chemistry and Physics Tuition/Physics Tutor

Experimental Techniques – Concise Notes

2.1 Measuring Physical Quantities
• An electronic balance is used to measure the mass of a substance.
• A stopwatch is used to measure time.
• Measuring cylinders, burettes, and pipettes are used to measure volumes of liquids.
• Degree of accuracy: Measuring cylinder (to the nearest 0.5 cm3), burette (to the nearest 0.05 cm3).
• A gas syringe is used to measure the volume of a gas.

2.2 Method for collecting gases
• Displacement of water is used for insoluble or slightly soluble gases, e.g. hydrogen, oxygen and carbon dioxide.
• Downward delivery is used for soluble gases that are denser than air, e.g. chlorine, hydrogen chloride and sulfur dioxide.
• Upward delivery is used for soluble gases that are less dense than air, e.g. ammonia. Drying agents
• Concentrated sulfuric acid — used for most gases except ammonia.
• Fused calcium chloride — used for most gases.
• Quicklime — used for ammonia gas.

2.3 Criteria of Purity
• Pure solids have fixed melting points.
• Pure liquids have fixed boiling points.
• An impurity will lower point and increase the boiling of a substance.

2.4 Methods of Separation and Purification
• Decanting and filtration are used to separate a solid from a liquid.
• Separating a mixture of solids can be carried out using a solvent, sublimation, or a magnet.
• Simple distillation is used to separate a liquid from a solution.
• A separating funnel is used to separate immiscible liquids.
• Fractional distillation is used to separate miscible liquids with different boiling points.
• Chromatography is used to separate two or more soluble components in a sample.

If you need help in the O level Chemistry, please contact Angie @96790479 or Mr Ong 98639633

[admin]

O-Level Singapore/O-Level/Pure Physics Tuition/Physics Tutor

Chapter 2 Kinematics Part 2

Exam Tip 4
Uniform acceleration means uniform increasing speed, i.e. the change of velocity (or speed) is a constant.

Exam Tip 5
Students should be able to describe the different kinds of motion of an object by reading distance-time or speed-time graph. They should be able to describe the change in distance, speed and acceleration

Exam Tip 6
Apply area formula for triangle, rectangle or trapezium according to the graph to find the distance travelled under the Velocity-Time graph

If you need help in the above topics, please contact Angie @96790479 or Mr Ong @98639633

[admin]

O Level Chemistry Tuition Singapore/Chemistry O Level Tuition/Tutor

Experimental Techniques – Concise Notes

2.1 Measuring Physical Quantities
• An electronic balance is used to measure the mass of a substance.
• A stopwatch is used to measure time.
• Measuring cylinders, burettes, and pipettes are used to measure volumes of liquids.
• Degree of accuracy: Measuring cylinder (to the nearest 0.5 cm3), burette (to the nearest 0.05 cm3).
• A gas syringe is used to measure the volume of a gas.

2.2 Method for collecting gases
• Displacement of water is used for insoluble or slightly soluble gases, e.g. hydrogen, oxygen and carbon dioxide.
• Downward delivery is used for soluble gases that are denser than air, e.g. chlorine, hydrogen chloride and sulfur dioxide.
• Upward delivery is used for soluble gases that are less dense than air, e.g. ammonia. Drying agents
• Concentrated sulfuric acid — used for most gases except ammonia.
• Fused calcium chloride — used for most gases.
• Quicklime — used for ammonia gas.

2.3 Criteria of Purity
• Pure solids have fixed melting points.
• Pure liquids have fixed boiling points.
• An impurity will lower point and increase the boiling of a substance.

2.4 Methods of Separation and Purification
• Decanting and filtration are used to separate a solid from a liquid.
• Separating a mixture of solids can be carried out using a solvent, sublimation, or a magnet.
• Simple distillation is used to separate a liquid from a solution.
• A separating funnel is used to separate immiscible liquids.
• Fractional distillation is used to separate miscible liquids with different boiling points.
• Chromatography is used to separate two or more soluble components in a sample.

If you need help in the O level Chemistry, please contact Angie @96790479 or Mr Ong 98639633

[admin]

O-Level Additional Mathematics Tuition Singapore

Exam Question 1

Find the values of k, for which -2x^2+kx-8 is always negative. [3 marks]

Ans -8 < k < 8 Exam Question 2 Given that 4x^2 - 6x + 9 = A(x - 1)(2x + 1)  B(x - 1) + C for all values of x, find the values of A, B and C. [3 marks] Ans A = 5, B = −4, C = 7 For exam based question with full worked solution, please contact Mr Ong @98639633 0r Angie @96790479

[admin]

O Level E Maths Tuition Singapore/Tuition O Level E Maths/Tutor

Addition and Subtraction of Fractions

1. Add/subtract the whole numbers first.

2. Find the lowest common multiple (LCM) of the fractions and convert them into fractions with the same denominators before adding/subtracting the fractions.

Example 1
3/5 + 1/4
= 12/20 + 5/20 (LCM is 20)
= 17/20

Example 2
-3 1/2 – (-2 2/3)
= -3 1/2 + 2 2/3
= -1 -1/2 + 2/3 (LCM 6)
= -1 -3/6 + 4/6
= -1 + 1/6
= -5/6

Multiplication of Fractions

1. Convert all mixed numbers to improper fractions first.

2. Simplify the fractions first by ‘cancelling’, to see if anything will divide into any of the top numbers and also the bottom numbers.

3. Multiply the numerators, then the denominators together

Evaluate

a) 8/9 x 3/4

b) -1 2/5 x 2/3

c) 2 1/2 x 3 1/5

Ans

(a) 2/3 (b) – 14/15 (c) 8

For Exam based questions with full worked solution. Please contact Mr Ong @98639633 or Angie @96790479

a

[admin]

A-Level Chemistry Tuition Singapore/H2 Chemistry Tuition/JC Chemistry Tutor

Chemical Bonding

Covalent Bond Strength
The strength of a covalent bond is measured by its bond energy (also called bond enthalpy) which is defined as the average energy absorbed when one mole of a particular bond is broken in the gaseous state.

The strength of a covalent bond is affected by the following factors:

(a) The effectiveness of overlap of the orbitals
In general, larger orbitals are more diffuse so that overlap is less effective in bonds formed by larger atoms compared to smaller atoms. For example the bond energies of chlorine to iodine are shown below.

BE(Cl—Cl): 244 kJ mol–1 BE(Br—Br): 193 kJ mol–1 BE(I—I):151 kJ mol–1

As the halogen increases in size, the valence orbital used in bonding is more diffuse so that the overlap of the orbitals is less effective from chlorine to iodine and bond energy decreases from chlorine to iodine.

Stop and Think

Question: Explain which bond is stronger, C—H or Si—H.
Answer: C—H bond is stronger since C is smaller than Si so that valence
orbital of C is less diffuse and overlap of its valence orbital with that
of H is more effective.

(b) The differences in electronegativities of the bonding atoms (bond polarity)

Electronegativity of an element measures the relative tendency of its atom to
attract the shared electron–pair in a covalent bond. Based on Pauling’s definition, fluorine, the most electronegative element, is given an arbitrary value of 4.0 and all values of the other elements are relative to it. The higher the value, the stronger the attraction.

Electronegativity decrease down a group.
Electronegativity increase­ across a period.

A polar covalent bond results if the bonded atoms have different electronegativities.

Partial charges (d+ and d–) arise on the two bonded atoms. The covalent bond is
described as possessing some ionic character.

For example in HF, F is more electronegative than H and hence attracts the
bonding electrons more strongly. The electron density distribution of the H—F
bond is asymmetrical and the H—F bond is polar, with F having a d– charge while
H having a d+ charge:

In addition to the existing covalent bond, there is now an increase in electrostatic attraction due to the two partial charges, which leads to increased bond strength.

In general, the greater the difference in electronegativity, the more polar is the covalent bond (i.e. greater the bond polarity) and stronger the covalent bond.

(c) Number of bonds between atoms (Single vs double vs triple bonds)

For the same bonding atoms, an increase in the number of bonds increases the
number of shared electrons between the two atoms i.e. there is increased
electrostatic attraction between the bond pairs and the two nuclei, hence bond
strength is increased.

Hence the strength of triple bond > double bond > single bond.

Bond Length
(i) The covalent bond length is the distance between the nuclei of the two
atoms in the bond.
(ii) Generally, the stronger the covalent bond, the shorter is the bond length.
(iii) The three factors of more effective overlap by less diffused orbitals, greater polarity of bond and increase in number of bonds between 2 atoms decrease bond length and increase bond strength.

A molecule with strong covalent bonds generally has less tendency to undergo
chemical change than does one with weak bonds. This is seen in nitrogen with its very large NºN bond energy (944 kJ mol–1). A very large amount of energy must be supplied to nitrogen to break the triple bond before nitrogen can react with other elements. Fluorine having a weak F–F bond (due to lone pair-lone pair repulsion in a very short bond) is very reactive.

Please contact Angie @ 96790479 or Mr Ong @ 98639633 if you need help in Chemistry

[admin]

A Level GP/General Paper Tuition Singapore

Due to popular demand, additional new class is added on Saturday

J1/J2 H1 Sat 3.30pm to 5.30pm

Please contact Angie @ 96790479 or Mr Ong @ 98639633 if you need help in General paper

[admin]

A-Level Biology Tuition Singapore/H2 Biology Tuition/JC Biology Tutor

TOPIC 3: GENETICS OF VIRUSES AND BACTERIA – Part 1

LEARNING OUTCOME

(a)Discuss whether viruses are living or non-living organisms and explain why viruses are obligate parasites.

ESSAY ANSWER

Arguments for Viruses being living

Arguments for Viruses being non-living

Possess genes/genetic material (DNA or RNA)

Have no cellular structure

Capable of reproducing by producing multiple copies of themselves

Cannot reproduce or carry out metabolic activities outside of a host
cell (e.g. ATP synthesis) and have no cellular machinery

Evolve by natural selection

Reproduce by assembly, not cell division

Why obligate?
Reproduce only within a host cell.

Contain only one type of nucleic acid (either DNA or RNA – which can be
single-stranded or double-stranded, but NOT both).

All viruses are parasitic.

Can infect and parasitize only a limited range of host cells.

For exam based questions and solutions, please contact Hp @9863 9633

[admin]

A-Level Physics Tuition Singapore/H2 Physics Tuition/JC Physics Tutor

Topic 1: Measurement Part 1

1.What are systematic / random errors? How can they be eliminated?

Systematic Errors

Errors of measurement which result in all readings being consistent overestimates or underestimates of its true value.

Cannot be reduced by taking repeated readings.

Can be reduced or eliminated by careful experimental design or good experimental techniques.

Examples: apparatus (zero errors, poor calibration), poor experimental technique (consistent parallax error), external factors (air resistance, background radioactive count rate).

Small systematic errors mean good accuracy.

Random Errors

Errors of measurement which cause an unpredictable scatter of readings about a mean value.

Can be reduced by taking repeated readings and finding the average

Cannot be eliminated.

Examples: Inconsistent reaction time, random parallax error, environmental conditions (fluctuations in measurement), limited sensitivity of instruments.

Small random errors mean good precision.

Please contact Angie @ 96790479 or Mr Ong @ 98639633 if you need help in Physics

[admin]

A-Level Economics Tuition Singapore/H2/H1 Economics Tuition

Guided Revision Test + Notes

Contents = Circular Flow of Income, PMI-ADAS-K, FP, MP and SSP

Section 1: Explanation Recall/Definitions

1) Explain briefly without definitions how each of the following factors affect
consumption
I) Government providing subsidies for parents on child care
II) Economic boom
III) Central bank increases interest rates
IV) Expectation of future inflation

2) Construct (USING PENCIL) the crude mechanism for the transmission of
Expansionary Fiscal Policy during a recession and a period of rising unemployment. In your diagram, indicate the limitations the policy may potentially face.

3) Construct (USING PENCIL) the crude mechanism for the transmission of Expansionary Monetary Policy during a recession and a period of rising unemployment. In your diagram, indicate the limitations the policy may potentially face.

4) In the balance of payments, if the sum of ________ items exceeds ______ items, the total currency inflow will exceed outflow, resulting in balance of payments _________.

5) In the balance of payments, if the sum of __________ items exceeds _______ items, the total currency outflow will exceed inflow, resulting in balance of payments _________.

6) Define circular flow of income and provide a diagram.

The circular flow of income illustrates the flow of ________ from households to
firms in return for the ________ that firms supply and the flow of __________ from firms to households in return for the _________ services that households supply.

Changes in circular flow of income are triggered by changes in injections and withdrawals. Injections are _________ to the circular flow of income which does not come from the expenditure of __________ _____________. Injections are ______________________________, _______________ ______________ and __________ ____________.

Withdrawals are any part of income that is not passed on within the circular flow of income.

Withdrawals include ___________, _____________ and ____________.

Diagram =

7) Further elaborate on the diagram circular flow of income. [Needed for all essays on circular flow]

Households supply their _________ of production in return for payments in the form of rent for land, ________ for labor, interests for ______ and _______ for their entrepreneurship. In addition, households also pay for goods and services produced by firms in the form of __________ expenditure. Households also receive help from __________ in the form of G, save some of the ________ they earn (S), pay ______ to the government and spend some on __________ goods (M).
Firms supply goods and services to households in return for household __________, which also become the _________ receipt for firms. Firms may also earn ______________ from selling exports to foreigners, or invest in new machinery in the form of __________ expenditure (I), receive subsidies from ____________ (G) and pay _______ (T) to government.In an economy, the equilibrium national income is achieved when the sum of ___________ from the circular flow of income is equal to the sum of ____________
into the circular flow of income. The mathematical expression for this is ___________________ = _______________.

8) Explain briefly what happens to circular flow of income of Singapore during a global financial crisis

P: The size of the circular flow of income will __________.

E/E: During a global financial crisis, there is a fall in global household income, causing the level of injections such as I and X to fall, thus Singapore’s national income is no longer in equilibrium because ___________________ > _________________.

The level of investment expenditure fell due to ___________ outlook by firms as
lower profitability of investment projects is expected during the global recession. In addition, banks are unwilling to lend during the financial crisis for fear of high ________ risks. Thus firms are unable to finance their investment projects, leading to fall in I.

The global recession leads to lower income and lower purchasing power for foreign households. Thus, the demand for Singapore’s exports fall, resulting in lower _______ __________ for the country.

During an economic recession, the Singapore government is likely to conduct an _____________ fiscal policy so that G will _________ .

However, the fall in I and X will more than offset the _________ in G. This is due to Singapore’s high trade dependence whereby X-M amounted to _______ of
Singapore’s GDP.

With the overall fall in injections, the firms output will decrease. The _______ demand for factors of production from _________ will decrease and according to the circular flow of income model, the __________ ___________ flowing back to households will _________, resulting in a fall in the size of the circular flow of income. With a lower income and purchasing power, households will cut ____________ __________ accordingly. At the same time, households will also _______ less, pay less __________ and spend less on _______ goods. The size of __________ will also fall.

With the fall in ____________ _____________ by households, firms will again
respond by decreasing _________. The process repeats and stops when the _______
fall in ________ is equal to the total fall in ____________.

L: Eventually the size of the circular flow of income decreases.

Please contact Angie Hp 96790479 or Mr Ong 98639633 if you need help in Economics and complete Notes

[Author]

Posts