heat

particle theory & changes of state Heating Curve:

particle theory & changes of state Heating Curve: A graph showing how a substance’s temperature changes while being heated The plateaus = when a change of state is occurring “Hidden Heat" = the energy required to change a substance’s state of matter; the energy is used to “free” particles from their previous state instead of warming the substance → therefore the temperature does not increase for a given amount of time and the graph indicates the plateau For water (ice to water to steam): → 0°C is the temperature at which ice (solid) begins to melt (and the plateau continues until all is water (liquid) → 100°C is the temperature at which water (liquid) begins to boil (plateau begins)

particle theory & changes of state Cooling Curve: A graph showing how a substance’s temperature changes while being cooled The plateaus = when a change of state is occurring For water (steam to ice): → below 100°C is the temperature at which steam (gas) begins to condense (plateau begins) → below 0°C is the temperature at which water (liquid) begins to freeze (and the plateau continues until all is ice)

HEAT AND CONVECTION Class Demonstration: A beaker of water with pepper was partially heated on a hot plate (pepper helps to see the movement of the water) Convection Current Demo.MOV On the heated side (left side): → addition of heat → water particles have more energy → particles move more quickly → have more collisions → particles take up more space → water is less dense → water rises On non-heated side (right side): → loss of heat → water particles have less energy → particles move more slowly → have less collisions → particles take up less space → water is more dense → water sinks

Heat and convection Convection = the transfer of heat by the movement of particles from one part of a fluid (liquid or gas) to another Convection current = the motion of many fluid particles cold dense water sinks – hot less dense water rises

HEAT AND weather patterns Thermals, Winds, Sea Breezes: The convection current in this case = thermal As thermals grow in size, drawing more and more cool air in at the bottom, people on the ground detect the flow of air as wind This wind most likely develops near large bodies of water (lakes, oceans) Water warms slower than soil, so the air over water tends to be cooler If the convection current is near a sea or an ocean, the wind that forms = sea breeze Thermals help large birds (eagles) glide in the air for hours; as warm air rises, birds ride it. If it isn’t strong enough to keep them aloft without effort, or they want to move to a new area, they glide down to the next thermal and start the cycle again

HEAT AND weather patterns Thermals, Winds, Sea Breezes:

HEAT AND weather patterns Large Wind Patterns: Huge convection currents are created by the sun in Earth’s atmosphere, causing global wind patterns to develop. One might expect winds at Earth’s surface to blow only from the poles to the equator… however, one factor affecting wind direction is Earth’s motion → Earth spins on its axis once each day → As it spins, the rising and falling air can also start to move in a curved or circular patterns → The result is that air moves in general patterns, but at a local level wind direction and strength are difficult to predict

HEAT AND weather patterns Large Wind Patterns:

HEAT AND weather patterns Large Wind Patterns: