Which physical property changes between 100 mL of water at 5°C and 100 mL of water at 45°C?

• A. Density
• B. Volume
• C. Chemical composition
• D. Molar mass

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the physical properties listed: density, volume, chemical composition, and molar mass. Density is mass per unit volume, volume is the space occupied, chemical composition refers to the types and ratios of atoms in a substance, and molar mass is the mass of one mole of a substance.
2. Step 2: Recognize that the chemical composition and molar mass of pure water do not change with temperature because the molecular structure and molecular weight remain constant.
3. Step 3: Consider the volume of water at different temperatures. Since the problem states the volume is 100 mL at both temperatures, volume is held constant by definition here.
4. Step 4: Recall that density depends on both mass and volume, and since the mass of water remains constant but volume can change with temperature due to thermal expansion, density will change as temperature changes.
5. Step 5: Conclude that the physical property that changes between 100 mL of water at 5°C and 100 mL of water at 45°C is density, because water expands when heated, decreasing its density.