🔍 Key Concepts

• Oil is less dense than water and tends to rise, while solid particles are more dense and tend to sink • In an inclined plate pack, surfaces are arranged so oil droplets and solids don’t have to travel far before they hit a surface • Think about which side of each plate oil would naturally attach to (rising) and which side solids would naturally attach to (sinking)

💭 Think About

• Visualize the separator in cross‑section: water flows between inclined plates, oil is trying to go up, solids are trying to go down. Which surface will each one touch first? • In the correct description, do oil droplets end up moving generally upward and outward, and solids generally downward and inward toward a sludge space? • Check each option: is it physically possible for something lighter than water to ‘sink’ or something heavier than water to ‘rise’ in a calm separating space?

✅ Before You Answer

• Make sure oil droplets always move in the direction of rising (upward), not sinking • Make sure solid particles always move in the direction of sinking (downward), not rising • Confirm the description where oil collects on the plate surface that faces upward and solids collect on the plate surface that faces downward relative to gravity.