Download PLACE LABEL HERE Tasmanian Certificate of Education

PLACE
LABEL
HERE
Tasmanian Secondary Assessment Board
Tasmanian Certificate of Education
External Assessment
1999
SC786 Physical Sciences
Time: Three Hours
On the basis of your performance in this examination, the examiners will provide a rating of A, B,
C or D on each of the following criteria taken from the syllabus statement:
Criterion 2
Convey scientific information and concepts using appropriate and
varied means of communication.
Criterion 7
Demonstrate knowledge and understanding of physics terminology,
conventions, quantities and units of measurement, definitions and
laws, concepts, theories and models.
Criterion 8
Use techniques of analysis and mathematical manipulation to solve
problems relating to physics concepts.
Criterion 9
Demonstrate understanding of current chemical theories explaining
the structure of matter and apply this knowledge to explain the
behaviour of unfamiliar substances.
Criterion 10
Understand the changes that occur in various chemical reactions
and use this knowledge to make qualitative and quantitative
predictions of the products of reactions, and generalise to novel
situations.
Questions:
Pages:
8
37
Copyright for part(s) of this paper may be held by individuals and/or organisations other than the Tasmanian Secondary
Assessment Board.
CANDIDATE INSTRUCTIONS
Any ONE Chemistry text and the Tasmanian Secondary Assessment Board Physical Sciences
Formula Sheet are allowed to be used throughout the examination.
No other printed material will be allowed into the examination.
An electronic calculator may be used.
The examination consists of EIGHT questions.
Each question is worth 20 points.
There are TWO questions on each of Criteria 7, 8, 9 and 10.
Make sure that you answer all questions to enable an assessment to be made on all criteria.
The quality and appropriateness of the presentation of your answers over the whole paper will be
used in arriving at an overall assessment for Criterion 2.
You should allocate about 22 minutes to each question.
All questions should be attempted in the spaces provided, unless otherwise indicated. If you need
more space use the blank page opposite the question. Show clearly that you wish it to be marked.
Otherwise you may use the blank pages for extra working.
Page 2
QUESTION 1 — This question assesses Criteria 7 and 2.
(a)
A ball is thrown vertically into the air, reaches its maximum height after 2 seconds and then
returns to its original position. In the table below briefly state what happens to the following
quantities during the time intervals shown. (Ignore air resistance.)
Quantity
from 1 s to 2 s
from 2 s to 3 s
speed
acceleration
potential energy
(3 points)
(b)
Explain why work is done when a hammer strikes a nail, driving it further into a wall, but
none is done when you push on the wall of a classroom.
................................................................................................................................................................................................
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................................................................................................................................................................................................
(2 points)
(c)
A boy playing by a river throws stones into the water so that they 'skip' across the surface
several times. Part of the path of one stone is given below:
A
water
'skip 1'
B
'skip 2'
surface
(i)
On the diagram above draw vectors to show the forces acting on the stone at point A and
point B.
(2 points)
(ii)
Discuss the energy changes occurring during 'skip 1', including impact at point B.
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(4 points)
Question 1 continues over the page
Page 3
Question 1 (continued)
(c)
(iii) The boy wants to make the distance of 'skip 1' larger. State 2 ways in which this can be
achieved if the stones are of similar shape and mass.
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...............................................................................................................................................................
...............................................................................................................................................................
...............................................................................................................................................................
(2 points)
(d)
Smoke detectors contain an alpha emitter, americium-241.
(i)
Write a nuclear equation to represent this decay.
...............................................................................................................................................................
...............................................................................................................................................................
(2 points)
(ii)
Why is this emission considered not dangerous to the occupants of dwellings which
contain such detectors?
...............................................................................................................................................................
...............................................................................................................................................................
...............................................................................................................................................................
(1 point)
(e)
Graphs to represent the activity of two samples of carbon-14, a radioactive element, are given
below:
activity
sample A
sample B
time
(i)
What constant can be determined from the graphs above?
...............................................................................................................................................................
(1 point)
(ii) Explain why the shape of the graphs is similar.
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(3 points)
Total:
Page 5
/20 points
QUESTION 2 — This question assesses Criteria 7 and 2.
(a)
Physics terms are often used incorrectly in our everyday life. Two such examples are given
below. Discuss fully what is incorrect about each statement.
(i)
A person is described as having 'a weight of 60 kg'.
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(2 points)
(ii)
In an advertisement describing a cordless drill kit, the phrase '9.6 volts of power' was
used.
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(2 points)
(b)
The forces acting on a sky diver in free fall after 3.0 seconds and after 20.0 seconds are given
by the vectors below:
at 3.0 seconds
(i)
at 20.0 seconds
Describe the overall or net force acting on the skydiver at each of the times indicated
below:
At 3.0 seconds: ......................................................................................................................................
...............................................................................................................................................................
At 20.0 seconds: ....................................................................................................................................
...............................................................................................................................................................
(2 points)
(ii)
Describe the motion of the skydiver at each of the times indicated below:
At 3.0 seconds: ......................................................................................................................................
...............................................................................................................................................................
At 20.0 seconds: ....................................................................................................................................
...............................................................................................................................................................
(2 points)
(iii) Sketch a graph on the opposite page to show how the velocity of the skydiver changes
with time.
(2 points)
Question 2 continues over the page
Page 7
Question 2 (continued)
(b)
(iv) At which of the times given in (b) (i) and (b) (ii) are Newton's First and Second Laws
demonstrated? Explain.
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(3 points)
(c)
The following equipment is available to a Physical Sciences student for building an electric
circuit:
one (1) 12 V battery
connecting wires
two (2) globes marked 18W/6 V
two (2) globes marked 6W/6 V
She built a circuit connecting the 12 V battery to one (1) of the 18W/6 V globes in series with
one (1) of the 6W/6 V globes. When the circuit was connected she observed that the globe
marked 18W/6 V was very dim and the one marked 6W/6V was much brighter.
(i)
If the order in which the globes are connected to the battery was reversed, would the
observations made be different? Comment.
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(1 point)
(ii)
Which globe is designed to operate at a higher current? Explain your choice.
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(1 point)
(iii) Explain the observations made about the relative brightness of the two globes.
(Calculations are not required when answering this question.)
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(2 points)
Question 2 continues over the page
Page 9
Question 2 (continued)
(c)
(iv) The student wants to construct a circuit containing two (2) globes chosen from the four
(4) supplied so that they are both of equal brightness and the battery will last for the
longest possible time when the circuit is connected. Draw a clearly labelled circuit
diagram below to represent the circuit she must build and explain your choice.
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(3 points)
Total
Page 11
/ 20 points
QUESTION 3 — This question assesses Criteria 8 and 2.
(a)
As soon as the lights turn green, a stationary car waiting at the traffic lights accelerates
uniformly at 3.6 ms-2 . Calculate:
(i)
the distance covered by the car during the first 3.0 seconds.
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(1 point)
(ii)
the speed of the car after it has covered a distance of 40 m.
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(2 points)
(iii) Later in the journey the driver checks the accuracy of the car's speedometer by timing
how long it takes to travel a marked 4 kilometre stretch of road whilst driving with the
speedometer reading 110 km hr −1 . It takes 2 minutes and 17 seconds to cover this
distance. Show that there is an error in the speedometer reading.
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(2 points)
(b)
A cricket ball of mass 160 g is hit towards a fielder. The fielder catches the ball bringing it
uniformly to rest from a velocity of 15 ms-1 over a time interval of 0.020 s. Determine:
(i)
the deceleration of the ball.
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(2 points)
(ii)
the change in momentum of the ball.
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(2 points)
Question 3 continues over the page
Page 13
Question 3 (continued)
(b)
(iii) the force the fielder applies to the ball to catch it.
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(2 points)
(iv) the distance through which the fielder's hands move as the catch is taken.
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(2 points)
(v)
the effect on the force applied to the ball by the fielder if the time taken for the catch is
reduced by a half.
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(1 point)
(c)
A cyclist is coasting down a hill, increasing his speed from 8.0 ms-1 to 12.0 ms-1 over the
2.0 km length of road he travels. He loses 100 m of height during this time. The combined
mass of the cyclist and the bicycle is 70 kg.
(i)
Calculate the change in potential energy.
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(1 point)
(ii)
Determine the work done against friction.
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(3 points)
(iii) Hence determine the frictional force.
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(2 points)
Total
Page 15
/ 20 points
QUESTION 4 — This question assesses Criteria 8 and 2.
(a)
A boy is told to walk to a campsite which is located 10.0 km south east of his present
position. He makes a mistake and walks 10.0 km south west.
(i)
Draw vectors on the same diagram to represent his intended path (label this A) and his
actual path (label this B).
(1 point)
(ii)
What is the straight line distance between the campsite and the boy after he has walked
in the wrong direction?
................................................................................................................................................................................................
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(1 point)
(iii) If he then takes 2 12 hours to walk to the campsite from his incorrect destination, what is
his average velocity for this part of the journey?
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(2 points)
(b)
Use the information given in the velocity~time graph below to answer the following
questions:
20
velocity
(ms -1 )
time (s)
0
10
15
17
-8.0
(i)
Sketch the corresponding acceleration~time graph on the opposite page.
(ii)
Determine the displacement of the object after 17 seconds.
(2 points)
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(3 points)
Question 4 continues over the page
Page 17
Question 4 (continued)
(c)
A laboratory technician was unknowingly exposed to a sample of iodine-131 contained in a
sodium iodide solution. The mistake was realised 32 days later when the activity was
measured as 9.5 x 10 6 Bq/g . The safety officer needed to determine the activity at the time of
exposure. If iodine-131 has a half-life of 8 days, calculate the activity of the sample at the
time of exposure.
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(3 points)
(d)
In the electrical circuit represented by the diagram below, 0.50A flows through the 15 Ω
resistor:
V
R
15
30
A
15V
(i)
What would be the reading on the voltmeter?
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(1 point)
(ii)
What current passes through the 30 Ω resistor?
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(1 point)
(iii) What would be the reading on the ammeter? ..................................................................................
(1 point)
(iv) What power is dissipated in the 15 Ω resistor?
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(1 point)
Question 4 continues over the page
Page 19
Question 4 (continued)
(d)
(v)
What is the value of the resistor, R?
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(2 points)
(vi) If the circuit is operating for 2 minutes, how much energy is dissipated in the 15 Ω
resistor?
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(2 points)
Total:
Page 21
/20 points
QUESTION 5 — This question assesses Criteria 9 and 2.
(a)
Complete the following table in the spaces provided.
Chemical formula
Name
Forces and/or chemical bonds
present
potassium sulfide
SiC
iron (III) oxide
(3 points)
(b)
Black phosphorus is a soft element which splits easily into sheets. Explain the likely structure
of this form of phosphorus.
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(2 points)
(c)
Oxygen, with 8 electrons in each atom, is able to bond with a wide variety of elements to
form compounds. Two compounds of oxygen are OCl 2 and Li 2O .
(i)
Draw an electron dot diagram of the compound OCl 2 .
(2 points)
(ii)
Explain how the bonding in these two compounds is different.
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(3 points)
(iii) Predict which compound is most likely to conduct electricity in the molten state.
Explain your choice.
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(2 points)
Question 5 continues over the page
Page 23
Question 5 (continued)
(c)
(iv) While the isotope of oxygen 168 O is the most common, the isotope 158 O also exists.
How do these isotopes differ in structure?
Does this cause a difference in the way they bond? Explain.
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(3 points)
(d)
The dihydrogen phosphate ion, H2 PO4 − can undergo each of the following reactions when
placed in water:
and
(i)
H2 PO4 − + H 2O → H3 O+ + HPO 4 2−
REACTION X
H2 PO4 − + H 2O → OH− + H3 PO4
REACTION Y
For each of the reactions represented above write the formula of the acidic and the basic
reactants:
REACTION X
REACTION Y
acidic reactant: ...................................... acidic reactant: .................................................
basic reactant: ....................................... basic reactant: ..................................................
(2 points)
(ii)
What special property does the H2 PO4 − ion exhibit in these reactions?
Explain how you came to your conclusion by referring to both equations.
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(2 points)
(iii) If a 0.10 M solution of NaH 2 PO4 has a pH of 4.1, which of the above reactions
predominates? Explain your answer.
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(1 point)
Total:
Page 25
/20 points
QUESTION 6 — This question assesses Criteria 9 and 2.
(a)
Complete the following table. The correct symbols have not been used for the elements in
column 1. When completing column 1, use the representation:
MassNumber
AtomicNumber
Χ, where Χ is the
symbol of the element.
Symbol of
isotope
Atomic
structure of
isotope
protons:..........
Electron
arrangement of
atom
electrons.........
neutrons: ........
41
Y
protons:
electrons:
neutrons:
Z
Symbol of usual
ion formed
(e.g. X 2 + )
Symbol of another
element with similar
chemical properties
2,8,8,1
9
9
10
(5 points)
(b)
Complete the following table by giving the structural formula, the molecular formula, the
empirical formula and the name of the compound as required in the blank spaces.
Structural formula
Molecular
formula
Empirical
formula
Name
CH2
pent-2-ene
H
H
H
H
C
C
H
Br
H
C
H
H
H
C
C
C
Br
H
H
C6H 12Br2
H
H
H
C
H
C
H
C
C
H
H
C
H
H
(6 points)
Question 6 continues over the page
Page 27
Question 6 (continued)
(c)
White corrector fluid, such as Liquid Paper™ consists of a white substance suspended in an
organic compound 1,1,1-trichloroethane. On application to paper a white residue remains
after the 1,1,1-trichloroethane evaporates.
(i)
Draw the structure of 1,1,1-trichloroethane.
(1 point)
(ii)
What type of forces and/or chemical bonds are present in the 1,1,1- trichloroethane?
Give an indication of the relative strengths of the forces as part of your answer.
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(2 points)
(iii) Draw and name one isomer of 1,1,1-trichloroethane.
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(1 point)
(d)
Electrical wiring used in houses consists of copper wire surrounded by plastic. What
properties of the copper and plastic are used in this construction of the wiring?
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(2 points)
(e)
Two allotropes of carbon, diamond and graphite, have been known for a long time. A third
allotrope of carbon, fullerines, has recently been isolated. One example of this group has the
formula C60 .
(i)
What does the number '60' signify?
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(1 point)
(ii)
Diamond is not given a similar formula. Why not?
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(2 points)
Total:
Page 29
/20 points
QUESTION 7 — This question assesses Criteria 10 and 2.
(a)
Calculate the molar mass of the following:
(i)
ammonium sulfate, (NH 4 )2 SO4 .
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(ii)
a substance in which 0.320 mole has a mass of 52.5 g.
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(3 points)
(b)
What is the percentage by mass of chlorine in the chemical phosgene, COCl 2 ?
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(2 points)
(c)
A laboratory technician has a bottle of sulfuric acid labelled '6.0 M'. She dilutes 200 mL of
this acid to prepare some 2.0 M acid.
(i)
How many mole are present in this volume of 6.0 M acid?
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(1 point)
(ii)
How much water must be added to the stronger acid in order to dilute the solution the
required amount?
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(2 points)
(d)
Calculate which of the following has the greater mass:
0.030 mole of carbon monoxide, CO
or
9.0 x 1021 molecules of chlorine.
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(3 points)
Question 7 continues over the page
Page 31
Question 7 (continued)
(e)
When excess sodium sulfate solution reacted with a known mass of hydrated barium chloride
dissolved in water the following chemical reaction occurs:
Na 2 SO4 (aq) + BaCl2 (aq) → 2NaCl (aq) + BaSO4 (s).
On analysis, it is found that 3.00 g of barium sulfate is obtained in the reaction.
[Some molar masses have already been calculated for you:
M(BaSO 4 ) = 233.4 g mol-1 ,
(i)
M(BaCl 2 ) = 208.3 g mol -1.]
Write an ionic equation to represent the above reaction.
................................................................................................................................................................................................
(1 point)
(ii)
How many mole of sodium chloride could also be obtained from this reaction?
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(3 points)
(iii) What mass of barium chloride, BaCl2 , must have been present in the crystals of the
hydrated salt?
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(2 points)
The mass of hydrated barium chloride, BaCl2 .x H2 O , dissolved in the water was 3.14 g.
(iv) What mass of water was present in the hydrated salt?
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(1 point)
(v)
Hence determine the value of x in the formula of the hydrated salt, BaCl2 .x H2 O .
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(2 points)
Total:
Page 33
/20 points
QUESTION 8 — This question assesses Criteria 10 and 2.
(a)
Write balanced chemical equations to represent each of the following:
(i)
Methane burns in oxygen to give carbon dioxide and water.
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(1 point)
(ii)
Nitrous acid (HNO2) is a weak acid in water.
................................................................................................................................................................................................
(1 point)
(iii) Solid magnesium carbonate reacts with a solution of hydrochloric acid.
................................................................................................................................................................................................
(2 points)
(b)
Predict what will happen in the following situations, writing appropriate equations as part of
your answer:
(i)
A solution of calcium nitrate is added to two test tubes, one containing sodium sulfate
and the other containing sodium chloride.
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(3 points)
(ii)
The pH changes in a soil sample when lime, Ca(OH)2 , is added to it.
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(2 points)
(c)
When ethene is placed in a steel vessel under appropriate conditions of heat and pressure, a
solid is formed. No such observation is made when ethane is placed in a similar vessel under
identical conditions. Explain these observations, including appropriate chemical equation(s)
as part of your answer.
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(3 points)
Question 8 continues over the page
Page 35
Question 8 (continued)
(d)
Bottles of cyclohexene and cyclohexane have lost their labels. Outline a chemical test which
could be completed by a Physical Sciences student in a school laboratory which will
positively identify cyclohexene. As part of your answer include the chemicals used, the
expected observations and the equation of any chemical reaction which occurs.
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(4 points)
(e)
A colourless solution X reacted readily with magnesium, releasing a colourless gas. When the
solution X was added to sodium sulfide an unpleasant smell was detected. On addition of
solution X to barium nitrate, a white precipitate was observed.
Identify solution X. Include relevant equation(s) in your answer.
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(4 points)
Total:
Page 37
/20 points