PAX PAX Chemistry and Physical Science 2 — Questions and Answers
Question 1: What happens during an exothermic reaction?
- Energy is absorbed from the surroundings
- Energy is released to the surroundings (Correct answer)
- No energy change occurs
- Temperature decreases
Correct answer: Energy is released to the surroundings
Exothermic reactions release energy (usually heat) to the surroundings, causing the temperature to rise.
Question 2: What is the formula for calculating density?
- Density = Mass + Volume
- Density = Mass / Volume (Correct answer)
- Density = Volume / Mass
- Density = Mass × Volume
Correct answer: Density = Mass / Volume
Density is defined as mass divided by volume (D = m/V) and is typically expressed in g/cm³ or g/mL.
Question 3: An acid and a base react to form water and a salt. This type of reaction is called:
- Oxidation
- Reduction
- Neutralization (Correct answer)
- Decomposition
Correct answer: Neutralization
A neutralization reaction occurs when an acid and a base react to produce water and a salt.
Question 4: What is Newton's First Law of Motion?
- Force equals mass times acceleration
- For every action there is an equal and opposite reaction
- An object at rest stays at rest unless acted on by an external force (Correct answer)
- Energy is neither created nor destroyed
Correct answer: An object at rest stays at rest unless acted on by an external force
Newton's First Law states that an object remains at rest or in uniform motion unless acted upon by a net external force (law of inertia).
Question 5: Which of the following is a chemical change?
- Ice melting
- Wood burning (Correct answer)
- Salt dissolving in water
- Glass breaking
Correct answer: Wood burning
Burning wood is a chemical change because it produces new substances (ash, COâ‚‚, water vapor) that cannot be reversed.
Question 6: What does the symbol 'Na' represent on the periodic table?
- Nitrogen
- Neon
- Nickel
- Sodium (Correct answer)
Correct answer: Sodium
Na is the chemical symbol for sodium, derived from the Latin word 'natrium.'
PAX PAX Chemistry and Physical Science 2
What happens during an exothermic reaction?