IMSO 2019 Science International - Theory II

Molting is a periodic shedding of the outer layer of an organism body. In a

field, you found a snail, a flatworm, a bee, a centipede, and a prawn.

a. List all the organisms above that molt?

b. Why do they need to molt?

Hermit crabs are crustaceans that inhabit snail shells. When a hermit crab

grows bigger, the shell will not be big enough for it. What would it do in this

situation?

Light, gas, and heat can be used to attract many kinds of insects. To effectively

attract female mosquitoes, a trap that releases gas is usually used.

a. What gas is commonly used to attract female mosquitoes?

b. Why does it attract female mosquitoes?

Plastic is a useful material for producing lots of things in daily life, such as

plastic bags. However, plastic pollution is a serious problem for our environment.

Identify 3 reasons why we should use glass bottles instead of single-use plastic

ones to reduce pollution and improve human health.

Deforestation is an activity of humans that is reducing the areas covered by

forests all over the world. Identify three reasons why we need to prevent the

deforestation to avoid the negative effects on our environment.

The figure below represents the water cycle in nature. Indicating the steps of

the cycle by writing down the numbers in the blanks before corresponding

processes.





(Adapted from https://www.theweek.in/)

A. \_\_\_\_\_\_ Collection

B. \_\_\_\_\_\_ Condensation

C. \_\_\_\_\_\_ Evaporation

D. \_\_\_\_\_\_ Precipitation

In the human digestive system, the absorption of nutrients is mostly taken place

in the (a)\_\_\_\_\_\_\_\_\_\_\_\_\_\_. The (b)\_\_\_\_\_\_\_\_\_\_\_\_\_\_ is mainly involved in

regulating the concentration of nutrients in the blood and helps eliminate

(c)\_\_\_\_\_\_\_\_\_\_\_\_\_ that are harmful to the body. Identify (a), (b) and (c).

In a village, nitrates from fertilisers applied to crops are leaked into the lakes.

a. What will happen with the amount of algae in the lakes?

b. What is the phenomenon called?

c. Why aquatic plants in the lake die due to that phenomenon?

d. Why fish living in the lakes die due to that phenomenon?

In an industrial area, a factory near the upstream of the river discharges high-
temperature waste into the river.





a. How would this discharge affect the number of animals and plants in the water?

b. If the untreated waste materials from factories include high amount of metals,

such as zinc and arsenic, and spread into the river. What will happen initially to

the town people who drink water from that river.

c. The residential area discharges organic matter to the river. How would the

concentration of dissolved oxygen change as water flows downstream from the

residential area?

d. Suggest two solutions without shutting down the factory to improve the quality

of water in that river.

The balance in blood glucose concentration helps your body enough energy

to do normal living activities. Blood glucose is controlled by two hormones,

insulin and glucagon, which are released by pancreas. What could happen to

blood glucose concentration if

a. higher level of insulin release

b. higher level of glucagon release

The human body requires vitamins to keep working well. The vitamins are

classified based on how they dissolve in your body. Based on the soluble-solvent,

classify the several vitamins into 2 groups in the table below by checking (✓) the

appropriate box.

| Vitamins | A | B1 | C | D | E | K |
| --- | --- | --- | --- | --- | --- | --- |
| Water soluble | | | | | | |
| Lipid soluble | | | | | | |

Electrical energy can be generated from different energy sources.
a. Examples of energy sources are: Gas, Wind, Oil, Solar, Wave, Hydro and Coal. These energy sources can be classified as renewable or non-renewable. Complete the table below to show which of these examples are renewable and which are non-renewable.

| Non-renewable | Renewable |
| --- | --- |
| | |

b. A coal-fired power station burns coal in order to generate electrical energy. A simplified diagram of a coal-fired power station is shown.

State the energy transformation that takes place in the:
i) Boiler

ii) Turbine

iii) Generator

Phong is a five-year old boy and is going to an elementary school in Hanoi
next year. He is very happy because his family has just had a new car. He wants
to discover the car and wonders how the speedometer works. Phong’s daddy tells
him that the reading from the speedometer shows the speed of the car at that
instant. The speed of the car is proportional to the rate of rotation of the tires.

a. Phong does not really understand how it is possible that the speed of the car is
proportional to the rate of rotation of the tires. Can you clarify that for him?

b. For a car with new tires, the speedometer shows accurately its speed. After a
year or so in using, the tires will wear, and their diameter will reduce an amount
of several millimeters. State and explain the effect, if any, from the reduction to
the reading of the car’s speedometer.

Linh set up an electric circuit with 4 identical bulbs and batteries, as shown
below.





She used 2 identical switches, S1 and S2, for controlling light bulbs B1, B2, B3,
B4 as shown in the following table.





a. In the circuit, put a slash ( / ) to identify the position of switches S1 and S2,
and label them with S1 and S2, respectively.

b. When switch S1 and S2 were closed, which one of the bulbs will have the
dimmest bulbs? Explain why.









c. Linh modified the circuit by replacing bulb B4 with an electric rod. After
modification, she closed all switches. She observed that bulb B3 did not light up
while bulb B1 and B2 still lighted up. Explain why.

Rod A is a steel bar XY. It was magnetized using the “stroke” method as
shown in diagram 1 below. Then, a magnet bar WZ was brought near to rod A,
which was tied to a string, as shown in diagram 2. Rod A moved away when the
magnet WZ was brought near it. A candle was placed under end Y of rod A, as
shown in diagram 3. After a while, rod A moved towards the magnet WZ.





a. Fill the name of magnetic pole (North or South) to the table below:

| Name of pole | Name of magnetic pole |
| --- | --- |
| X | |
| Y | |
| Z | |
| W | |

b. Explain why Rod A started to move towards the magnet WZ in diagram 3.










c. One of home applications of magnet is audio speaker, which transforms
electrical signal into an audible sound. Speakers contain: a moving metal coil, a
stationary permanent magnet, and a cone made of a flexible material such as
paper or plastic. These are arranged as shown in the diagram below:





A metal coil, also known as electromagnet, is placed in front of a permanent
magnet. The electromagnet is attached to the cone. Explain how speaker works?

A King’s crown has a volume of 110 cm³ and a mass of 1,800 g. The density
of gold is 19.3 g/cm³. Is the crown pure gold? Prove your answer.

In the figure below, hot weather caused the expansion and cracking of the
concrete. Explain this phenomenon.

Two balls of the same size and shape are dropped from a helicopter. One ball
has twice the mass of the other ball. On which ball will the force of air resistance
be greater when terminal velocity is reached?

In annular eclipse, the Sun appears as a bright ring surrounding the dark disk of
the Moon, as shown in the figure. Annular eclipse is a special case of solar
eclipse. When it occurs, the Moon, the Sun and the Earth are exactly in line.
In this eclipse:

a. What is the relative position between the Moon, the Sun and the Earth?

b. Is the Moon about the farthest or shortest distance from the Earth?

c. Explain why we do not have a solar eclipse every month even though the Moon

orbits the Earth one cycle in a month.