Density and Pressure in GCSE Science

Introduction

• Discusses the concept of pressure in the context of density and materials.
• Details how to calculate density and pressure of different materials.

Density

• Definition: Mass per unit volume of an object.
  • Symbol: ( \rho ) (rho).
• Example: A golf ball is denser than a beach ball.
• Relevance: Determines if an object floats or sinks in water.
  • More dense than water: Sinks
  • Less dense than water: Floats
• Dependence: Based on material, not shape or size.
• Calculation: Density ( = \frac{\text{mass (kg)}}{\text{volume (m}^3)} ).

Pressure

• Definition: Force per unit area.
• Example: Stepping on a pin concentrates force on a small area, causing more pressure.
• Calculation: Pressure ( = \frac{\text{force (Newtons)}}{\text{area (m}^2)} ).
• In Fluids:
  • Pressure increases with depth due to the weight of particles above.
  • Analogy: Human pyramid - more force felt at the bottom.
  • Water in a bucket: Lower holes experience greater pressure and force.

Pressure Difference

• Measurement: Compares gas or liquid pressure to atmospheric pressure.
• Device: Manometer
  • Structure: U-shaped tube filled with liquid.
  • Function: Height difference of liquid determines pressure difference.

Interesting Fact

• Airplane food tastes different due to low pressure and humidity.
• Sensitivity to sweet and salty flavors drops by 30% at high altitudes.
• Umami taste is heightened under these conditions.