Floating and Sinking Whatever floats your boat!

Warm-up 1. Observe the two beakers on the front table and record your observations. 2. Predict- will the ice sink or float? 3. Watch the demonstration. 4. Explain your observations after watching the demonstration.

Measuring Objects Mass – amount of ‘stuff’ or matter in an object. Mass – amount of ‘stuff’ or matter in an object. Volume – amount of space something takes up Volume – amount of space something takes up

Calculating Density To calculate mass – triple beam balance or scale To calculate mass – triple beam balance or scale Units = g or kg Units = g or kg To calculate volume – length x width x height, or graduated cylinder. To calculate volume – length x width x height, or graduated cylinder. Units = cm 3 or ml Units = cm 3 or ml To calculate To calculate Density = MASS Density = MASS VOLUME VOLUME Units = g/cm 3 or g/ml Units = g/cm 3 or g/ml

Sinking or Floating In order for something to float, it must be less dense than the fluid in which it is immersed. In order for something to float, it must be less dense than the fluid in which it is immersed. Density of water = 1.0 g/cm 3 Density of water = 1.0 g/cm 3 Example: oil and water Example: oil and water Is oil more or less dense than water? Is oil more or less dense than water?

Sinking If an object is more dense than the liquid, it will sink If an object is more dense than the liquid, it will sink Ex: lead, steel, fishing weight, etc… Ex: lead, steel, fishing weight, etc… Submarine can change it’s density by taking in, or pumping out water. Submarine can change it’s density by taking in, or pumping out water. Ex: cartesian diver. Ex: cartesian diver.

Buoyancy Buoyancy is the upward force produced by a fluid that acts on an immersed object. Buoyancy is the upward force produced by a fluid that acts on an immersed object. Ex: boats floating, figure 10, p. 427 – jellyfish, turtle, and lobster Ex: boats floating, figure 10, p. 427 – jellyfish, turtle, and lobster A fluid exerts pressure on all surfaces of a submerged object. A fluid exerts pressure on all surfaces of a submerged object. Since pressure increases with depth, the pressure acting on the bottom of the object is greater. Since pressure increases with depth, the pressure acting on the bottom of the object is greater.

Archimedes Principle Archimede's Principle: The buoyant force is equal to the weight of the liquid displaced. Archimede's Principle: The buoyant force is equal to the weight of the liquid displaced. Immersion: all or part under water. Immersion: all or part under water. Submersion: completely under water Submersion: completely under water

Measuring Buoyant Force and Volume of Solids To measure buoyant force – must measure weight of water displaced in Newtons. To measure buoyant force – must measure weight of water displaced in Newtons. To measure volume of irregular shaped object: it is equal to volume of water displaced. To measure volume of irregular shaped object: it is equal to volume of water displaced.

Amount of Buoyancy Buoyant force is determined by the density of the fluid and the density of the object. Buoyant force is determined by the density of the fluid and the density of the object. More dense fluid = more buoyant force More dense fluid = more buoyant force Ex: salt vs. fresh water Ex: salt vs. fresh water Less dense object = higher the object floats. Less dense object = higher the object floats. Density also changes with heat Hot water is less dense than cold water. Hot air less dense than cold air. This is why cold air sinks, hot air rises. Density also changes with heat Hot water is less dense than cold water. Hot air less dense than cold air. This is why cold air sinks, hot air rises.