1. NAT Reviewer
Grade 12 Science

2. Microwaves were invented during World War II when radar technology
was being developed. In the last 40 years, the microwave oven has
become a ubiquitous appliance. Microwave technology enables us to
thaw and cook food much more rapidly than conventional appliances
do. The cooking action in a microwave oven results from the interaction
between the electric the field component of the radiation with the
polar molecules—mostly water—in food. All molecules rotate at room
temperature. If the frequency of the radiation and that of the
molecular rotation are equal, energy can be transferred from the
microwave to the polar molecule. As a result, the molecule will rotate
faster. This is what happens in a gas. In the condensed state (for
example, in food), a molecule cannot execute the free rotation.
Nevertheless, it still experiences a torque (a force that causes rotation)
that tends to align its dipole moment with the oscillating field of the
microwave. Consequently, there is friction between the molecules,
which appears as heat in the food. (Source).

3. Which of the following statements best describe
why microwaves heat food so quickly?
A. The radiation is absorbed by nonpolar molecules
that created friction and will generate heat in food.
B. The radiation is absorbed by polar molecules and
can, therefore, reach different parts of food at the
same time.
C. The polar molecules in foods when exposed to
radiation will heat and cooks the food.
D. The nonpolar molecules in foods when exposed
to radiation will heat and cooks the food.

4. Read the following information and answer the question below.

5. Which of the following statements is correct about food
containers that are utilized and safe for microwaves?
A. They do not contain polar molecules and are
therefore not affected by microwaves.
B. They contain polar molecules and are therefore affected
by microwaves.
C. They do not contain nonpolar molecules and are
therefore not affected by microwaves.
D. They contain nonpolar molecules and are therefore
affected by microwaves

6. A student heated a beaker of cold water (on a tripod) with an
alcohol lamp. When the gas is ignited, the student noticed that
there was water condensed on the outside of the beaker. Which
of the statements best described the observation?
A. The gases from the environment react with the heat from the
alcohol lamp and condense.
B. The gases from the alcohol lamp condense on the outside of
the cold beaker.
C. The water from the container seeps into the wall of the beaker.
D. When methane burns in the air, it forms carbon dioxide and
water vapor. The water vapor condenses on the outside of the
cold beaker.

7. 17. Suppose you are hiking in one of the mountains of
Bukidnon. Upon reaching your destined area, you
decide to hard-boil an egg and eat it to help regain
your strength following the strenuous work. To your
surprise, the water seems to boil more quickly than
usual, but after 10 min in boiling water, the egg is still
not cooked. Due to a decrease in atmospheric
pressure, it takes less energy to bring the water to its
boiling point. Hence due to less energy needed, the
water boils at a lower temperature. The summit of the
mountain is 9,511 ft above sea level. At this altitude,
the atmospheric pressure is only about 0.7 atm.

8. Figure 1 below shows how pressure affects the melting
point and boiling point of water.
Figure 1. This phase diagram tells us that increasing the pressure on ice lowers its
melting point and that increasing the pressure of liquid water raises its boiling point.

9. Which of the following statements best described your
observation?
A. The amount of heat delivered is inversely proportional to
the temperature of the water, so it takes a longer time to hard
boil the eggs.
B. Because water boils at a lower temperature at high
altitudes, hard-cooked eggs will take longer to prepare.
C. At higher altitudes, the air pressure is higher, so the boiling
point of water decreases thus needing more time in cooking
eggs.
D. At higher elevations, the higher atmospheric pressure
means heated water reaches its boiling point more quickly.

10. In 1985 a British chemist named Alec Jeffreys
suggested that minisatellite sequences provide
a means of identification, much like
fingerprints. DNA fingerprinting has since
gained prominence with law enforcement
officials to identify crime suspects.

11. To make a DNA fingerprint, a chemist needs a sample of any tissue,
such as blood or semen; even hair and saliva contain DNA. The DNA
is extracted from cell nuclei and cut into fragments by the addition
of so-called restriction enzymes. These fragments, which are
negatively charged, are separated by an electric field in gel. The
smaller fragments move faster than larger ones, so they eventually
separate into bands. The bands of DNA fragments are transferred
from the gel to a plastic membrane, and their position is thereby
fixed. Then a DNA probe—a DNA fragment that has been tagged
with a radioactive label—is added. The probe binds to the fragments
that have a complementary DNA sequence. An X-ray film is laid
directly over the plastic sheet, and bands appear on the exposed
film in the positions corresponding to the fragments recognized by
the probe. About four different probes are needed to obtain a
profile that is unique to just one individual.

12. The first U.S. case in which a person was
convicted of a crime with the help of DNA
fingerprints was tried in 1987. Today, DNA
fingerprinting has become an
indispensable tool of law enforcement.
Source: Chang, Raymond, Overby, Jason. (2022). Chemistry Fourteenth
Edition. New York: McGraw-Hill (adapted)

13. 18. The following statements explain how DNA profiling
(fingerprinting) can be used to identify people by their
unique genetic code EXCEPT.
A. identify suspects whose DNA may match evidence left at
crime scenes
B. clear persons wrongly accused of crimes
C. identify fathers in paternity cases
D. identify unknown remains using ashes.

14. Which of the following is the correct order for obtaining a DNA
fingerprint?
I. X-ray fil detects radioactive patterns. These patterns are then
compared to the original sample.
II. DNA is extracted from the blood sample, then the restriction
enzymes cut DNA into fragments
III. Fragments are separated by gel electrophoresis and the band
pattern is transferred to a nylon membrane
IV. Radioactive DNA probe binds to specific DNA sequences
A. III, II, I, IV B. I, III, IV, II C. II, III, IV, I D. IV, I, III, II

16. Which of the statements regarding enzymes is
true?
A. Enzymes cannot be used for a specific
reaction.
B. Enzymes provide activation energy for
reactions.
C. Enzymes are proteins that function as
catalysts.
D. Enzyme activity cannot be regulated.

17. Which of the following best describes the role of a
catalyst in a chemical reaction?
A. A substance that is being used during a chemical
reaction.
B. Catalysts increase the activation energy of a
chemical reaction.
C. A catalyst decreases the speed of a reaction and
lowers product yield.
D. A substance that speeds up a chemical reaction
without being used up.

18. To make bread dough, a cook mixes flour, water, salt
and yeast. After mixing, the dough is placed in a
container for several hours to allow the process of
fermentation to take place. During fermentation, a
chemical change occurs in the dough: the yeast (a
single-celled fungus) helps to transform the starch and
sugars in the flour into carbon dioxide and alcohol. A
few hours after mixing the dough, the cook weighs
the dough and observes that its weight has
decreased. The weight of the dough is the same at the
start of each of the four experiments shown below.

20. Which two experiments should the cook compared
to test if the yeast is the cause of the loss of
weight?
A. The cook should compare experiments 1 and 2.
B. The cook should compare experiments 1 and 3.
C. The cook should compare experiments 2 and 4.
D. The cook should compare experiments 3 and 4.

21. The bread consumed will be degraded, or broken down, in our bodies to
provide energy for growth and function. A general overall equation for this
very complex process represents the degradation of glucose (C6H12O6) to
carbon dioxide (CO2) and water (H2O):
If 500.0 g of C6H12O6 is consumed by a person over a certain period, what is
the mass (in gram, g) of CO2 and H2O produced? ( 6C12.01 1H1.01 8O16.0 )
The chemical reaction is C6H12O6 + O2 CO2 + H2O
A. 311.2 g CO2 and 650.0 g H2O C. 732.8 g CO2 and 300.0 g H2O
B. 150.0 g CO2 and 903.4 g H2O D. 545.20 g CO2 and 447.0 g H2O

22. Four boxes contain different organisms. Box
A has organism with a waxy cuticle to
protect it against water loss. Box B contains
organism with Xylem and Phloem. Inside
Box C is an organism with connective tissues
like cartilage, blood, bone, and adipose. Box
D has organism with unspecified tissues. Its
tendons are covered with Xylem and
phloem while its hairs are attached directly
to its bones with no epithelial tissues at all.

23. Which of the following boxes
contains an animal?
A. Box B B. Box C
B. C. Box A D. Box D

24. Which of the following boxes
contains organism that is NOT a
plant?
A. Box C B. Box B
C. Box E D. Box A

25. Which of the following tissue can also be found
in Box A and B?
A. Muscular Tissue C. Neural Tissue
B. Vascular Tissue D. Epithelial Tissue

26. An unidentified flying object (UFO) has cells with a
typical nucleus with a nuclear envelope, where its
DNA lies inside it and is commonly linear. It does not
have mesosomes yet contains Golgi apparatus. Which
of the following statements best describes this UFO?
A. The UFO is a prokaryote.
B. It is a kind of bacteria.
C. It definitely possesses a eukaryotic cell.
D. It is probably an alien with indistinct feature.

27. •Plants and animals may reproduce either sexually or
asexually. In both cases, this is the reason why species
survived for thousands of years. Just like any other
vertebrates for example, human reproduce sexually by the
joint of a sperm cell and egg cell to form embryo. On the
other hand, some organisms like bacteria and sponges
reproduce having no gametes involved. Yet, there are also
exceptional cases that some organisms may reproduce
like for example those honey bees and even earthworms
are called hermaphrodites. However, unlike animals,
reproduction in plants specifically in Gumamela is unique
and is termed double fertilization.

28. Which of the following scenario is TRUE?
A. Honey bees are some of the viviparous
organisms.
B. Earthworms have both male and female
reproductive organs.
C. Sponges give birth through live placental
birth.
D. Bacteria are some of the oviparous
organisms.

29. Why is fertilization in Gumamela plants
termed as double fertilization?
A. Only those complete flowers may have
double fertilization.
B. All plants both have male and female parts.
C. Only those perfect flowers can have double
fertilization.
D. Since there are two sperm cells involved in
the fertilization of egg cell and two polar
bodies.

30. •Thirdy’s botanical garden seemed to amuse the locals
of Bukidnon. However, there are times that his plants
are attacked by some pathogens thereby becoming
vulnerable. One of them is the mayana particularly its
leaves. Luckily, there are some plants that can resist
diseases. Unlike its neighbor plants, the entire kalabo
plant, gabon- gabon, asunting, and lagundi are
resistant to infection. Sometimes, there are also
herbivores that roam around which created mess
inside the botanical garden. Thirdy noticed that these
herbivores seemed to have eaten specific plants
while refusing some.

31. Which of the following immune responses do
kalabo plant, gabon-gabon, asunting, and
lagundi possess?
A. Basal response
B. Hypersensitive response
C. Systemic acquired immunity
D. Jasmonic acid/ethylene pathway