Bellwork  1) Name all the steps of the water cycle.  2) How does water from the ocean turn into a cloud? What are the steps?

Objective for the day  By the end of the day…  SWBAT describe heat transfer and air pressure in the atmosphere.

Convection Currents Review Density goes down Density goes up

Heat transfer in the troposphere  Key Point #1: Radiation, conduction, and convection work together to heat the troposphere.  Radiation: heat transfer through empty space  Conduction: heat transfer through direct contact  Convection: heat transfer through a fluid (liquid or gas)  Key Point #1: Radiation, conduction, and convection work together to heat the troposphere.  Radiation: heat transfer through empty space  Conduction: heat transfer through direct contact  Convection: heat transfer through a fluid (liquid or gas)

Heat Transfer in the Troposphere  Where do you find radiation in the atmosphere?  From the sun  Where do you find conduction?  The sun heats the ground, which then heats the air.  Where do you find radiation in the atmosphere?  From the sun  Where do you find conduction?  The sun heats the ground, which then heats the air.

Questions  Where do you find radiation in the atmosphere?  From the sun  Where do you find conduction?  The sun heats the ground, which then heats the air.  Where do you find convection?  When the air is heated from the ground, the molecules start a convection current in the air. Convection causes most of the heating in the troposphere.  Where do you find radiation in the atmosphere?  From the sun  Where do you find conduction?  The sun heats the ground, which then heats the air.  Where do you find convection?  When the air is heated from the ground, the molecules start a convection current in the air. Convection causes most of the heating in the troposphere.

Properties of Air  Air has mass.  Key Point #2: Because air has mass, it also has other properties, including density and pressure.  Air has mass.  Key Point #2: Because air has mass, it also has other properties, including density and pressure.

 Mass is often given in grams (g)  Volume is often given in milliliters (mL)  Therefore, density is given in grams/milliliters (g/mL) MMass is often given in grams (g) VVolume is often given in milliliters (mL) TTherefore, density is given in grams/milliliters (g/mL)

#1 Practice: What is the density if the m=10g and v=2mL?

#2 Practice: What is the volume if the d=2g/mL and m=6g?

#3 Practice: What is the mass if density=4 g/mL and v=2 g/mL?

Pressure  The force pushing on an area or surface is known as pressure.  Key Point #3: Air pressure at a certain point is the amount of weight of a column of air pushing down at that point.  The force pushing on an area or surface is known as pressure.  Key Point #3: Air pressure at a certain point is the amount of weight of a column of air pushing down at that point.

Pressure  Denser air exerts more pressure than less dense air. Denser air = MORE air pressure Less dense air = LESS pressure Denser air = MORE air pressure Less dense air = LESS pressure

Think-Pair-Share  What is the relationship between the temperature of air and how much pressure it has?  Hotter air has a LESS air pressure.  Cooler air has MORE air pressure. Denser air = MORE air pressure Less dense air = LESS pressure Denser air = MORE air pressure Less dense air = LESS pressure

Temperature/Density/Pressure HOT air =  Density = Pressure COOL air= Density = Pressure  If Density goes down, Pressure goes down. If Density goes up, Pressure goes up.

Measuring Air Pressure  Air pressure is often measured in millibars, just like weight is often measured in pounds.

Increasing Altitude  Key Point #4: The higher you are, the lower the air pressure is.  Air pressure is greatest as sea-level.  Why?  Sea-level air has the weight of the whole atmosphere pressing on it.  Key Point #4: The higher you are, the lower the air pressure is.  Air pressure is greatest as sea-level.  Why?  Sea-level air has the weight of the whole atmosphere pressing on it.

Think-Pair-Share Look back at your Key Point #3. Now how does altitude relate to density?  Increasing altitude decreases density.

 Which has the greatest air pressure?  Which has the least air pressure?  Which has the greatest density?  Which has the least density? A B C

Exit Ticket 1. Describe what air pressure at a certain point means. (Think of the stack of books) 2. Does denser air have more or less air pressure? Explain. 3. If air in California near the shore is 80 °F, and air in Florida near the shore is 88 °F, which state has the greater air pressure? Explain your reasoning.