ONE-EIGHTH STAGE 2024
ONE-EIGHTH STAGE, ROUND 5 RIDDLES
Adonten SHS: 50 points
West Africa SHS: 36 points
Kumasi Secondary Technical School: 27 points
ROUND 5 - RIDDLE
RIDDLE
I am a well-known nuclide.
I am known for my stability.
I am the standard for molecular mass.
ANSWER: Carbon-12
EXPLANATION:
Carbon-12 is a stable nuclide and is the defined reference for the atomic mass unit: 1 amu $=\dfrac1{12}$ the mass of a carbon-12 atom.
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PRACTICE QUESTIONS
1. RIDDLE:
I am an isotope.
I have one proton and one neutron.
I am about twice as heavy as ordinary hydrogen.
Water made with me is called heavy water.
I am a fuel for nuclear fusion.
My symbol is D.
Who am I?
ANSWER: DEUTERIUM
EXPLANATION:
Deuterium, ²H, is the stable heavy isotope of hydrogen.
2. RIDDLE:
I am a radioactive nuclide.
I have 92 protons.
Slow neutrons make my nuclei split.
I fuel nuclear reactors.
I make up less than 1% of my natural element.
I powered the first atomic bomb used in war.
Who am I?
ANSWER: URANIUM-235
EXPLANATION:
U-235 is the fissile isotope of uranium.
3. RIDDLE:
I am radioactive.
I have six protons and eight neutrons.
I am made in the upper atmosphere from nitrogen.
My half-life is about 5730 years.
Archaeologists use me to date ancient wood and bones.
I am a heavier isotope of the element in diamond.
Who am I?
ANSWER: CARBON-14
EXPLANATION:
C-14 decays with a half-life of about 5730 years, which is used in radiocarbon dating.
4. RIDDLE:
I am an isotope of the lightest element.
My nucleus holds one proton and two neutrons.
I am radioactive.
I decay into helium-3 by beta emission.
I make some watch dials glow.
My symbol is T.
Who am I?
ANSWER: TRITIUM
EXPLANATION:
Tritium, ³H, is the radioactive isotope of hydrogen.
5. RIDDLE:
I am a radioactive isotope.
I give out strong gamma rays.
I am used to treat cancer.
I sterilise medical equipment.
My element has 27 protons.
My half-life is about 5.3 years.
Who am I?
ANSWER: COBALT-60
EXPLANATION:
Co-60 is a gamma emitter used in radiotherapy and sterilisation.
6. RIDDLE:
I am a radioactive isotope.
My half-life is about eight days.
My element collects in the thyroid gland.
I am used to diagnose and treat thyroid disease.
I was released in the Chernobyl accident.
My element is a halogen with 53 protons.
Who am I?
ANSWER: IODINE-131
EXPLANATION:
I-131 is a beta emitter taken up by the thyroid.