2024-2025 Physical Science

Imagine you are an astronomer studying the origins of the universe. You observe that galaxies are moving away from each other, indicating an expanding universe. Based on this observation and the possible existence of a primordial atom, which widely accepted theory explains the universe's origin?

• Oscillating theory

• Big Bang theory

• Divine creation theory 

• Steady state theory 

As a swirling mass of gas and dust contracts under gravity, its core experiences rising temperatures and pressure. Just before a fundamental shift occurs, a defining moment marks its transition to the next stage. Which of the following best signifies this critical turning point?

• When hydrogen nuclear fusion begins

• When the temperature rises enough to ignite hydrogen

• When it starts spinning faster

• When it begins to emit light

When does a star start displaying unpredictable and unstable behavior?

• When it undergoes cycles of contraction and expansion

• When gravity pulls the outer layers toward the star's center

• When its fuel supply is exhausted

• When its core is converted to iron

What term describes a one-dimensional point where an enormous amount of mass is concentrated in an infinitely small space?

• Nucleosynthesis

• S-process

• Singularity

• R-process

Calculate the number of electrons in a lithium atom, assuming its mass number is approximately 6.491.

• 3

• 6

• 9

• 12

​ ​ Polar bonds can result in nonpolar covalent compounds depending on molecular geometry ​ ​

• true
• false

Evaluate the following statements about molecular polarity:

Statement 1: A molecule with a polar bond is always polar.

Statement 2: Molecules consisting of polar bonds can be nonpolar.

• Statement 1 is true, while Statement 2 is false.

• Statement 1 is false, while Statement 2 is true.

• Both statements are true

• Both statements are false

Electronegativity describes an atom's ability to attract shared electrons from other molecules.​

• True
• False 

What type of chemical bond formed between hydrogen and chlorine, given their electronegativity values of 2.1 and 3.0.

• Hydrogen bond 

• Ionic bond

• Polar Covalent bond

• Nonpolar Covalent bond

Determine the mass number of an atom that has 3 protons, 4 neutrons, and 3 electrons.

• 3

• 4

• 7

• 10