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What is a single covalent bond?

1. ATwo pairs of electrons shared between two atoms
2. BOne electron transferred from one atom to another
3. CThe attraction between two oppositely charged ions
4. DOne pair of electrons shared between two atoms

What does the prefix "milli-" mean?

1. AOne-hundredth (10⁻²)
2. BOne thousand (10³)
3. COne-thousandth (10⁻³)
4. DOne-millionth (10⁻⁶)

แถวแนวตั้งของตารางธาตุเรียกว่าอะไร

1. Aหมู่
2. Bชั้น
3. Cคาบ
4. Dอนุกรม

How does a catalyst speed up a reaction?

1. AIt provides a different pathway with a lower activation energy
2. BIt makes the reaction more exothermic
3. CIt adds extra reactant to the mixture
4. DIt raises the temperature of the reactants so they move faster

When the diaphragm contracts and the chest cavity gets bigger, what happens to the air pressure inside the lungs?

1. AIt does not change
2. BIt falls, so air flows out
3. CIt rises, so air flows in
4. DIt falls, so air flows in

At 20 °C, about 36 g of NaCl dissolves in 100 g of water. If 50 g of NaCl is stirred into 100 g of water at 20 °C, what happens?

1. AAbout 36 g dissolves and about 14 g stays undissolved
2. BNone of the salt dissolves
3. CAll 50 g dissolves
4. DAbout 14 g dissolves and about 36 g stays undissolved

Which 1-litre solution lowers the freezing point of water the most?

1. A1 M NaCl
2. B0.5 M NaCl
3. C1 M CaCl₂
4. D1 M glucose

What fraction of a radioactive isotope remains after three half-lives?

1. A1/6
2. B1/3
3. C1/9
4. D1/8