PSLE Science Chemistry Topics 2 — Questions and Answers
Question 1: Which method is best for separating salt from a saltwater solution?
- Filtration
- Magnetic separation
- Evaporation (Correct answer)
- Sieving
Correct answer: Evaporation
Evaporation removes the water, leaving the dissolved salt behind as solid crystals — the same method used in salt pans.
Question 2: What is a solution?
- A mixture where solid particles are visible at the bottom
- A uniform mixture where one substance dissolves completely in another (Correct answer)
- A mixture of two liquids that do not mix
- Any mixture of two or more substances
Correct answer: A uniform mixture where one substance dissolves completely in another
A solution is a homogeneous (uniform) mixture where the solute dissolves completely in the solvent and cannot be seen.
Question 3: Which separation method would you use to remove sand from a sand-and-water mixture?
- Evaporation
- Filtration (Correct answer)
- Magnetic separation
- Distillation
Correct answer: Filtration
Filtration passes the mixture through filter paper, which traps the insoluble sand while allowing water to flow through.
Question 4: Which mixture can be separated effectively using a magnet?
- Salt and sugar
- Sand and salt
- Iron filings and sand (Correct answer)
- Rice and water
Correct answer: Iron filings and sand
Iron filings are magnetic and are attracted to a magnet, allowing them to be pulled away from the non-magnetic sand.
Question 5: In a saltwater solution, what is the solvent?
- Salt
- Water (Correct answer)
- The solution itself
- Salt and water equally
Correct answer: Water
Water is the solvent because it is the substance in which the salt (solute) dissolves to form the solution.
Question 6: What happens when you mix oil and water in a container?
- Oil dissolves completely in water to form a clear solution
- Water floats on top of oil because water is less dense
- Oil floats on top of water because oil is less dense and they do not mix (Correct answer)
- They mix evenly to form a uniform solution
Correct answer: Oil floats on top of water because oil is less dense and they do not mix
Oil is less dense than water and the two liquids are immiscible (do not mix), so oil always floats on top of water.
Question 7: Which of the following substances is NOT soluble in water?
- Sugar
- Salt
- Sand (Correct answer)
- Baking soda
Correct answer: Sand
Sand is insoluble in water — it sinks to the bottom and does not dissolve, unlike sugar, salt, and baking soda.
PSLE Science Chemistry Topics 2
Which method is best for separating salt from a saltwater solution?