1989-01-26 — Page 20

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CENSUS

1989 中學會考幀習專業

嶼邇出版社

MILL & DALE PRESS

Economics (18)

Alain Li

Census means an official counting of the population, collecting demographic, economic and social data, in Hong Kong,

a census is taken goce very 10 years.

and a by-census is taken in between 2 census.

The importance of a census

The significance of a census Following areas:

the

B

1989 中學會預習專欄

明演出版社

MILL & DALE PRESS

Chemistry (18)

R Chu

Unit 10: Revision Notes on. Enthalpy changes of Reactions and Rates of Reactions

ENTHALPY, CHANGE OF REACTIONS

2.

All chemical reactions accompained by energy changes.

Formulating population policy

The information about birth rate,. death rate, fertility rate, sex ratio and age groups shows whether the population is changing ata rate appropriate, to economic and social conditions. Then the government knows whether it should. encourage

discourage... family planning.

or

2. Regulating population movement

From the information on emigration' and immigration, the government may Counteract the undesirable consequences of population movement. One emigration relation problem now facing, Hong Kong is brain drain (1885.

3. Housing and rent control

From the information on housing and rent, together with the population projection, the government. may estimate the number of housing

8... Thermometric Titration

The essential reaction neutralization is

H2 (=q)+0x ̃(aq) →→820(1)

which is exothermic. Thus, when an. acid is added slowly to a given amount of an alkali in a reaction vessel, e.g., a polystyrene cup, the temperature of the mixture will \rise"gradually until the alkali is totally reacted. If the temperature

the mixture is plotted against the volume of the acid added, a graph as shown below is obtained.

Traperture falls Beauté ng more reaction, tekmu ploce {ienta, ag” more; det Devolves to furthän addition

oi cole aald esols down the

tica statica

are

at turn GI

tenseraturs

·places,

•Maxfrum temperaturn

If the energy change in a reaction his measured at a constant pressure, it is known as the enthalpy change, denoted as A. P

An exothermic reaction is one an which energy has to be lost by the reacting system to the surrounding in order to return to its initiall conditions of temperature and presure. Its All has a negative value.

An exothermic reaction is one in which energy has to be gained by -the reacting. system from the surrounding in order to return to

اني

its initial conditions temperature and pressure. Its All has a positive value.

Frergy Level Diagrams of Reactions.

Exothermic Reaction

senates the end-pain-

RATES OF CHEMICAL REACTIONS 1.1. Reactions

proceed 3 different- rates under different conditions. 1.2. Reaction rate is a measure of the

don't co

reaction which occurs in

4.

5.

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units required for the population

and determine whether rent control. is required.

Economic policy-making

The information about the labour force; labour force participation rate, unemployment rate, industrial occupational: distribution and, distribution, is valuable. to the government to planning its economic policy...

Manpower planning and development The information on the literacy rate and level of educational eltainment of the population may help the government in manpower planning and development to fulfill future economic and social needs.. The Population of Hong Kang

At the end of 1987, Hong Kong had a population of 5658810 people but only e

2.

Points to be noted:

the

(1) The steeper the curve, Caster is the reaction rate. Hence, rate at ion his greater thiết that at Qfor ') ....

(ii) The fat portion denotes the completion of the reaction.

The collision Theory a simple model of reactions

2.1 The reacting particles must collide

before they can react.

via very

2.2 Only a very small fraction of such collisions can actualy induce chemical reaction. This fraction of. collisions is known as effective collisions.

2.3 Effective collisions are collisions

possessing a certain minimum amount. of energy called the activation energy, Ea, of the reaction.

2.4 The rate of reaction is directly the number of proportional tự effectivecollisions in unit volume

turas: por unit time, which in depende re

(i) the collision frequency the -Aumber of collisions in voltwolupe

per unit time and

(ii) the fraction of the being effective.

Thus,

1.3-Consider the topothetical reaction

below,

Rate C

collision frequency

Fraction of collisions being effective

Increase in amount (or

concentration) of the product

time interval

1.4 The reaction rate can be obtained from a concentration (or amount)- time graph.

for "amevant)

2.5 Diagrammatic presentation of the

Collision Theory

e.g. A2(g) +B2(y)→→→→2AB(g)

四期星日六廿月一(九八九一)年八十七國民華中 (20)

land area of 1071 square kilometres. The overall population density per square kilometre was 5262. As compand will the population of 4631500, in 1977, there has been an increase of 22 per cent

natural increase in. The rate of population dropped steadily from 12 per thousand in 1977 to 8 per thousand in 1987. This was. the result of λ declining birta rate, from 18 per thousand in 1977 to 13. per thousand- in 1987, and a stable death rate, at about -5 per thousand.

The reason why the population increasec the rate of natural increase While declined. was the influx of Chinese' Immigrants and vietnamese refugees.

The AA distribution has considerably...

Table 18.1 refers.

Energy Endotherly Reaction

Bond forintng

Bend

Jarcasing

Products Alfre

Reactants

changed

Reaction

ה

Aga roun

1977

1987

14

4

65.3%

9.73

د الله باز باران

The proportion of people of working age, i... those between 15 and 64, has increased by 4.4%. They are said to be economically active! and can help to improve the national income of Hong the Kong. Besides,

population has become older. Regarding geographical distribution, according to the 1986 by-census, the censity in the metropolitan arease was 20811 per square kilometre and that in the New Territories was 1449 per square kilometre. This situation will change with the continuing development of the new towns

in the New Territories, designed to alleviate "the high density. in the urban areas.

N.B. (1) In exothermic reactions: energy released in bond- forming is greater than that absorbed breaking.

Main Factors affecting the Reaction Rates

Factor's

Effects

14 Concentration of (a) Råte increases as

concentration reactant(s)

increases.

2. Temperature

13. Pressure

tonly fastang reactions

muotuing go

(b) Rate decreases, as concentration decreases.

(a) Rate increases as

temperature increases.

(b) Rute decreases as,

temperature decreases.

(c) A rise of 10K in

temperature

usually doubles' the rate.

(a) Rate increases as

pressure increases. (b) Rate decrcases as

pressure decreases.

a

in band-

(2) In endothermic reaction: energy released in bond- forming is smaller than that absorbed in bond- breaking.

Interpretation

An increase in concentration of the reactant increases collision frequency. of the reacting particles due to decrease in their distances, so, the rate increases. The reverse. is also true.

a

A rise in temperature increases. the velocities, and hence the kinetic energy, of the reacting particles, thus increasing both The collision frequency and the fraction of collisions which is effective, SO, increases.

true.

increase

the rate The reverse also

pressure, An

to according

Law,. Boyle's reduces the volume occupied by

a

gasebus reactart; this is. equivalent to increasing

its

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Energy

Beactants,

Products.

Reaction-

Endothermic Reactíoní

or,

Products

Beactants

Reection

A spontaneous reaction must

exothermic because it has

smal value of Ea; buts an

exothermic reaction. is

not

necessarily spontaneous.

The enthalpy change of a reaction

is the energy change which occurs

when the amounts of the substances as indicated by the

chemical equation for the. reaction are completely reacted at a constant pressure,

AH=-92.4k3 7.

It means that when 2 moles of

nitrogen gas. react comoletely with.

3 moles of hydrogen gas to give 2

moles of ammonia gas, 92.4kJ of) heat, will be evolved:

1989 中學會考預習專欄:

明德出版社

MILL & DALE PRESS

Biology (17)

Nervous System and Tropisms

A Cheuk

The diagram below shows the human brain in longitudinal section), spinal cord in transverse section) and right hand. The parts are, not drawn to scale,}

Spinal

cor'd

旅遊

效廣法刊明香三 刊告律登令港 物之性有指政

有質關定府

本

oject

Reaction rate

Decrease in amount for concentration) of the reactant A time interval

cocentrati

Reaction rate at time, t-slope of

the curve at t.

(i) Name Cand state its function in the transmission of nerve impulse.

(i) Name the fluid contained in D and state its function.

Name (iii) (1)

E and gi.ve function of this part of the brain.

a

(2) Why is its surface folded sc much?

(iv) Now does the distribution of nerve cell bodies in brain differ from the spinal cord.

(v). What is the response of the human subject when touching the hot object?

(vi) Name, in the correct order, the nerve neurones involved in the reflex action in part (v).

(vii) State two advantages of the type of response, in (v).

(viii)State two functions of the cerebellum of the marcial Fan- brain.

(ix) Name A and B and state their

functions..

He reaction

resulted

Energy

8.8

Energy

14. Catalyst

Particle size of solid reactent(5)

Reaction resulted

16. Nature of

reactant(s)

2.6 The Energy Profile Diagrams

Energy Exothermic Reaction

1Bond

breaking

energy

abscrbad?

도래

Reactants.

Bohe tormlog

Tolergy released)

2. An experiment was set up asing the apparatus as shown in the diagrams. Seedling A: radicle untreated. Seedling : tip of radicle removed. Seedling C: radicle untreated,

(i)

Porous

pot

water

Empty

cust

With respect to growth and curvature of the radicles of seeding A, B and C, what Changes, if any, would be observed after a few days? (11) What conclusions can be drawn from the observation in (i) for (1) seedling A and B, (2) seedling A and C.

describe

the..

advantage. which growing

(x):

What would be the effect if the nerve fibre has been cut in (1) position X, (2) position Y.

(iii) Briefly

plants gain from the response shown by seedling: A.

1.

(a) A positive catalyst.

ncreases the rate. (b) A negative catalyst

(or inhibitor) decreases the rate.

(a) Rate is fast if

particle sizes are

(b) Rate is slow if

article sizes are Target

(a) Reactions involving

aqueous ions are Usually, fest.

b) Reactions involving Convalent molecules are mostly slow and require more vigorous conditions

Methods of Following Reaction Rates.

The methods employed to follow the rate of a reaction depend mainly on the

of characteristics particular reaction.

Solution

the

[+ ensures that nerve (i) Synapse.

impulses can only be transmitted in one direction only. 1.c. from the axon of one neurone to the dendron of another neurons. (11)Cerebro-spinal fluid. It provides nutrients and oxygen to the nerve cell's. It also protects and provides mechanical support to the spinal cord and brain. (iii) (1) Cerebral cortex.

It acts as the site of higher : mental activities Such as

memory, imagination.

(2) [t is Folded to increase surface area of .the. grey matter which .results 17 increased co-ordination and localization of functions in the cerebral cortex.

(iv) The

cell bodies are nerve distributed outside in brain tut they are enclosed inside the white matter in the spinal cord.

(v) The right. hand bends

the by contraction of the flexor muscle. (vi)Sensory neurone relay neurone→

motor neurone.

{visit is rapid and protective. (viii) It co-ordinates the contraction

muscles of the skeletal perform precise movements

to and

maintains the balance of the body.

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the

concentration and hence collision Frequency: Thus, the rate increases:

The reverse is also true.

A positive catalyst increases the rate of a reaction by providing an alternate. pathway of Tower activation energy, thus increasing the fraction of collisions which is effective. A negative catalyst just gives the opposite effect.

The more finely-divided a given mass of a solid reagent, the greater is the surface area of contact and hence the greater. is the rate. The reverse is also true.

time for it takes much more breaking and forning. the covalent bonds.

e.g. the disappearing of a

reactant,

the appearing of a product. the volume of the gas formed,

-the colour change. stc.

| (ix)

As a

sensory neurone which carries nerve impulses from the receptor to the central nervous system.

Bis ત motor neurone which transmits nerve impulses From the. central nervous system to the. system to the effector.

(x) (1)The brain does not receive the pain sensation but the withdrawal reflex proceeds. (2) The brain receives the pain sensation but 10 withdrawal reflex.

(i) Seedling A: the radicle continues to grow and bends towards the porous pat. Seedling B: the radicle has no further growth or bending.

Seedling C the radicle continues to grow downwards without bending.

tip Of radicle (ii) (1) The

is responsible for the growth and curvature.

(2) It shows that the radicle tends to grow in the direction It with a supply of water, also shows that the effect of the .stimulus of water 15

stronger than that of gravity.

(iii) It helps the seedling to obtain

water,

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Page 20Page 21

美國纵民师涛张八大九六)

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