Paiseh.. I accidentally post this answers in another blog. Sorry for the delay. Here is the post.

Section A [30]

Section B [40]

Qns 1 (2m) :

(a) Gas has fewer particles than an equal amount of a solid or a liquid ;

(b) When the substance is heated, the particles start to move faster and further apart. ;

Qns 2 (8m):

(a) (i) FeSO₄ ;

(iii) C₄H₉OH ;

(b) (i) Mg + 2 HCl à MgCl₂ + H₂ ;

(ii) C₃H₈ + 5 O₂ à 3 CO₂ + 4 H₂O ;

(iii) Fe₂O₃ + 3 CO à 3 CO₂ + 2 Fe ;

(c) (iv) Mass number of X = 19 + 20 = 39 ;

(v) No ;

(vi) X has more protons than electron, thus it must be a positive ion ;

Qns 3 (6m) :

(a) Our body cells need certain substances and only small, soluble molecules are able to pass through the cell membranes. ;

(b) (i) Hydrochloric acid ;

(ii) The acid helps to provide the suitable pH for the enzymes or to kill harmful bacteria

(iii) Chewing the antacid increases the surface area of the antacid that helps to speed up the process of neutralization. ;

(c) The walls of the small intestines have many finger-like structures called villi. The villi increased the surface area for absorption. ;;

Qns 4 (4m):

(a) X: Sperm duct ;

Y: Urethra ;

(b) (i) testis ;

(ii) penis ;

Qns 5 (5m):

(a) Diagram B and D ;;

(b) In figure B, the light does not travel in straight line. ;

In figure D, the angle of incidence is not equal to the angle of reflection. ;

Qns 6 (4m) :

(a) The plastic sheet vibrates and a sound is heard. ;

The sand particles vibrate as well and ‘jump’ up and down on the plastic sheet. ;

(b) The plastic sheet and the sand particles will vibrate faster and a higher pitch sound is produced. ;

The shorter tuning fork has a higher frequency or more vibrations per second. ;

Qns 7 (2m) :

(a) leaves à caterpillar à mynas à owls ;

Qns 8 (5m):

(a) (i) The piece of dry ice had disappeared. ;

(b) (i) hydrogen + oxygen à water ;

(ii) calcium + oxygen à calcium oxide ;

Qns 9 (4m) :

(a) It ensures that carbon dioxide and other carbon compounds do not run out and are always available for living things to use. ;

Secondly, it helps to keep the amount of carbon in the ecosystem constant so that there is neither too much or too little of it in the ecosystem. ;

(b) Decomposers help to break down dead animals into simpler substances, returning the substances from the body into the soil so that plants and animals can use it again. ;

In the process, it also releases carbon dioxide gas into the atmosphere. ;

Section C

Qns 1

(a) (i) The water level in glass tube 1 will rise while the water level in glass tube 2 will fall. ;

(ii) The concentrated sugar solution has less water molecules than the weak sugar solution, therefore water will diffuse into the tubing, causing the water level to rise. ;

The weak sugar solution has less water molecules than water and thus water will diffuses out of the tubing, resulting in the water level to fall. ;

(ii) The water level in glass tube 1 will remain unchanged, as water molecules will diffuse both in and out of the tubing. ;

The water level in glass tubing 2 will fall further as compared to the previous experiment as more water molecules will diffuse out of the tubing. ;

(b) In the mouth, the bread is chewed into smaller pieces and mixed with saliva ;

The amylase in saliva digested part of the carbohydrates in the bread into simple sugars.

The tongue then rolled the partially digested bread into small balls and swallowed it. ;

The pancreas then secretes amylase to further digest starch into glucose. ;

The rest of the starch from the bread is then digested in the small intestine. ;

Qns 2

(a) Every month, an egg from the ovary will ripe/mature and at the same time, the uterus becomes thicker and has more blood.

If the ripe egg is not fertilized by a sperm, it will dies and be discharge out from the vagina. ;

The thick lining of the uterus will not be needed and it will be shedded out together with the egg.

This removal process is known as menstruation and last from three to seven days. ;

(b) (i) Either one of the answers in the table below is acceptable.

(and any other suitable answers)

( ; for method and ; for advantage)

Qns 3

(a) (i) Chemical change ;

This change is irreversible. The iron combined with oxygen in the air to form iron oxide (rust). ;

(ii) Both chemical and physical ;

The combustion of the wax with oxygen to form carbon dioxide and steam is irreversible.

The melting of the wax is reversible as it is only a change in state. ;

(b) (i) sulphur dioxide, nitrogen oxides, carbon monoxide and smoke particles ;;

(ii) Form acid rain ;

Causes breathing difficulties and may lead to lung cancer or brain damaged if exposed for long-term ;

Causes diseases like tuberculosis(TB), bronchitis ;

Reduced plant growth by destroying chloroplasts in green plants that is used in photosynthesis. ;

(Either 3 of the 4 answers above)

Qns 4

(a) To measure the electric current flowing through a light bulb in a circuit, simply connect an ammeter in series with the light bulb and the voltmeter to be across the light bulb as shown in the diagram below. ;

(ii) the overall resistant in the circuit decreases ;

the total current increases and thus the brightness of the bulb also increases ;

(a) Time in used = 45 mins = 0.75 h ;

Energy consumed = 2 (kW) x 0.75 h ;

= 1.5 kWh

Cost of electricity = 1.5 kWh x 0.18 ($/kWh)

= $0.27 ;