States of Matter Determined by Temperature Thresholds

Steps:

• Below melting point, substance is solid; between melting and boiling points, liquid; above boiling point, gas.
• At -10°C: greater than melting point (-17°C) but less than boiling point (117°C), so liquid.
• At 10°C: greater than -17°C and less than 117°C, so liquid.
• Both temperatures fall within the liquid range.

Why C is correct:

• The liquid state exists between melting point (-17°C) and boiling point (117°C), per phase transition definitions.

Why the others are wrong:

• A: Assumes solid at -10°C, but -10°C exceeds melting point.
• B: Claims gas at 10°C, but 10°C is below boiling point; also wrong on -10°C.
• D: States gas at 10°C, but 10°C is below boiling point.

Final answer: C