WS 8.2 answers

II.   Fill in the blanks:

1.     What is an electric current?

Ø   In some materials, there are electrons which are free to move around randomly. These electrons are called (1) free electrons.

Ø   The free electrons in a metal wire move (2) randomly in all directions when there are no dry cells in the circuit.

Ø   The free electrons in a metal wire are ‘driven’ to flow in the (3) same direction when there is a dry cell in the circuit.

2.     Measuring electric current

Ø   An (7) ammeter is an instrument used for measuring the size of an electric current.

Ø   Electric current is measured in (8) ampere(A). Small electric currents are measured in milliamperes (mA).

Ø   We should always connect the (9) positive terminal of the ammeter towards the positive pole of the dry cell and the (10) negative terminal towards the negative pole.

Quiz 6: WS8.1 answers

Fill in the Blanks (9 marks)

1      Dry cell stores chemical(1) energy which can be converted into electrical energy

2      A path for electricity to flow through is called a circuit(1).

3      A circuit which is complete is called a closed circuit(1).          

4      A circuit which is incomplete is called an open circuit(1).

5      Materials that allow electricity to pass through are called electrical conductors(1).

6      Materials that do not allow electricity to pass through are called electrical insulators(1).

7      Metals(1) are electrical conductors while most non-metals(1) are electrical insulators.

8      We use a switch(1) to open or close a circuit.

Challenging Questions (Bonus 3 marks)

1.      List TWO necessary conditions for electricity to flow.

A source of electrical energy(1) and a closed circuit(1)

__________________________________________________________________________________

2.      What non-metal can allow electricity to pass through?

Graphite(1)

__________________________________________________________________________________

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Worksheet 8.1 answers

II.   Fill in the blanks:

1.     Conditions for electricity to flow

Ø   Sources of electrical energy:

²  Dry cell stores (1)chemical energy which can be converted into electrical energy;

²  Electrical energy can also be supplied from the power station to the appliance through the socket.

Ø   A path for electricity to flow through is called a (2) circuit.

²  A circuit which is complete is called a (3) closed circuit.

²  A circuit which is incomplete is called an (4) open circuit.

2.         Electrical conductors and insulators

Ø   Materials that allow electricity to pass through are called electrical (5)conductors.

Ø   Materials that do not allow electricity to pass through are called(6) insulators.

Ø   (7)Metals are electrical conductors while most (8)non-metals are electrical insulators.

3.     Switches

We use a (9)  switch to open or close a circuit.  

what is voltage and current

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Workbook Integrated Exercise (P.39)

4.        (a)    (i)     B to C, D to E

                (ii)    N to P, R to T

        (b)    The chest volume decreases while the gas pressure inside the chest increases.

        (c)    (i)     The intercostal muscles relax, causing the ribs move downwards and inwards. Hence, the volume inside the chest decreases.

                (ii)    The diagram moves upwards, thus the volume inside the chest decreases.

Workbook Answer 7.6

Section 7.6

A. Multiple choice                                                                                                         p.23-24

E        1.     D

E        2.     D

E        3.     D

E        4.     C

B. Fill in the blanks                                                                                                              p.25

E     (a)    contract

(b)    upwards

(c)    outwards

(d)   downwards

(e)    increases

(f)    decreases

(g)    relax

(h)    inwards

(i)     downwards

(j)     upwards

(k)    decreases

(l)     increases

C. Matching                                                                                                                         p.25

E     (a)    v

(b)    i

(c)    ii

(d)   vi

(e)    iii

        (f)    iv

Long Q3-2

c. 以下實驗顯示光合作用的某些條件. 位置P和S是綠色的, Q和R是非綠色部分. 位置R和S被鍚紙覆蓋.

i. 測試澱粉後, 位置P, Q, R和S的顏色如何?

ii. 位置Q在實驗完結時不含有澱粉, 為什麼?

iii. 位置R在實驗完結時不含有澱粉, 為什麼?

iv. 從實驗可以得出什麼結論?

1st term test long Q1

題解:

當自發粉(baking powder)與水混合後會釋出Gas X, 此氣體由hydrogencarbonate indicator測試, 而顏色由紅色轉為黃色.

a. 提出氣體X是什麼?

b. 如果氣體收集並倒在蠟燭的火焰上, 會發生何事? 解釋你的答案.

c. 如果自發粉加在有水生植物的水盤內, 這會如何影響光合作用的速率? 解釋你的答案.

Long Q3-1

3. 下圖顯示測試一塊綠葉的過程.

a. 利用A-F 正確排列上圖的次序.

b. 解釋A, B, D和E步驟的目的.

1st term test Long Q2

a. 在以上的實驗, 花生屬於火三角的什麼部分?

b. 舉出花生在以上實驗的能量轉變.

c. 以上實驗有一個過程發生, 當中花生儲存的能量會釋出.

i. 這個過程的名稱是什麼?

ii. 寫出一個文字方程式, 以顯示發生於花生的改變.

d. 利用以上裝置, 比較5g花生和5g餅乾的能量值, 列出3個要維持不變的變項(variable)

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1415 UT performance

Workbook Quick Review (P.42-44)

A

(a)    Fuel

(b)    Temperature

(c)    Oxygen

(d)   goes out

B

(a)    (i)     light energy

        (ii)    chlorophyll

  (iii)     water

(b)    (i)     carbon dioxide

        (ii)    oxygen

  (iii)     oxygen

        (iv)   carbon dioxide

C

   (a)    (i)     Air

         (ii)    lungs

   (b)    (i)     Oxygen

   (ii)    carbon dioxide

(c)    (i)     Chemical

  (ii)    oxygen

        (iii)   carbon dioxide

(d)   (i)     less

        (ii)    more

  (iii)   less

  (iv)   more

  (v)    lower

  (vi)   higher

(e)    (i)     glowing splint

        (ii)    colourless

        (iii)   milky

        (iv)   red

        (v)    yellow

        (vi)   blue

        (vii)  pink

D

(a)    photosynthesis

(b)    oxygen

(c)    respiration

(d)   carbon dioxide

Workbook Integrated Exercise (P.30-39) answers

Workbook Integrated Exercise (P.30-37) answers

A

1.     True

2.     True

3.     False

4.     True

5.     True

E6.     False

E7.     True

8.     False

B

1.     C

2.     C

3.     D

4.     D

5.     D

6.     A

E7.     C

8.     D

C

1.     (a)    ii, iii, v, vii

   (b)    i, iv, vi, viii

2.     (a)    iii, iv

   (b)    ii, v

           (c)    i, vi

D. Questions  p.36-41

1.     (a)    (i)     oxygen

(ii)    Put a glowing splint into the test tube. If it relights, it shows that the gas is oxygen.

(iii)   It is used to provide carbon dioxide for the water plant to carry out photosynthesis.

        (b)    (i)     The rate of bubbling increase.

                (ii)    The rate of photosynthesis increases when the light intensity increases.

2.     (a)    (i)     It remains colourless. It shows that no carbon dioxide is present in the air entering the bell jar.

(ii)    It changes from red to yellow. It shows that the mouse releases carbon dioxide.

(b)    Sodium hydroxide solution absorbs carbon dioxide from the incoming air. This ensures that the colour change of the indicator in flask C is due to carbon dioxide released from the mouse.

        (c)    (i)     Place the set-up in the dark. (or other reasonable answers)

(ii)    Without light, the plant cannot undergo photosynthesis. This ensures that the experimental result is due to respiration of the plant only. (or other reasonable answer)

3.     (a)    (i)     Respiration: food + oxygen ----=>   carbon dioxide + water energy

                (ii)                                                                    light energy

                        Photosynthesis: carbon dioxide +water --------------=>  food +oxygen

                                                                                        chlorophyll

        (b)    (i)     The rate of net oxygen absorption will be negative.

                (ii)    The rate of net oxygen absorption will be positive.

        (c)    (i)     From 0600 to 1800

                (ii)    From 1800 to 2400 and 0000 to 0600

E4.     (a)    (i)     B to C, D to E

                (ii)    N to P, R to T

        (b)    The chest volume decreases while the gas pressure inside the chest increases.

        (c)    (i)     The intercostal muscles relax, causing the ribs move downwards and inwards. Hence, the volume inside the chest decreases.

                (ii)    The diagram moves upwards, thus the volume inside the chest decreases.

Workbook Answers 7.5

A

1.     B

2.     C

3.     C

4.     D

5.     C

B

(a)

Tube	Does respiration take place? (ü / û)	Does photosynthesis take place? (ü / û)	Colour of the indicator	The level of carbon dioxide (unchanged / increase / decrease)
A	ü	ü	red	unchanged
B	ü	ü	purple	decrease
C	û	û	red	unchanged
D	ü	û	yellow	increase
E	ü	û	yellow	increase
F	ü	û	yellow	increase
G	û	û	red	unchanged
H	ü	û	yellow	increase

(b)    In the dark, the plant does not undergo photosynthesis. However, both the plant and snail carry out respiration which gives out carbon dioxide. Therefore, the level of carbon dioxide increases and the indicator changes from red to yellow.

(c)    Under bright light, there is a net intake of carbon dioxide in plants. In the dark, there is a net release of carbon dioxide in plants.