Limited Time Offer: Get 2 Months of for only $5!

6th Grade Science- Chapter 5 Notes

Chapter 5, Lesson 1 Notes

*Earth is a system made up of different parts.  The atmosphere is the envelope of gases that surround the planet.  The hydrosphere is made up of all the water on Earth.

*The atmosphere and hydrosphere constantly interact.  For example, when energy from the sun warms the gases in the atmosphere and the water in the hydrosphere, the water evaporates and forms vapor in the atmosphere.  The vapor may form clouds and then fall back to the surface of Earth as rain.

*The condition of Earth’s atmosphere at a particular time and place is weather.  As the interactions between Earth’s parts change, so does the weather.

*All substances are made up of tiny particles (atoms and molecules) that are constantly moving.  The faster the particles move, the more energy they have.

*Thermal energy measures the total energy of motion in the particles of a substance.

*Temperature is the average amount of energy of motion of each particle of a substance.

*Air temperature is usually measured with a thermometer.  A thermometer is a device that measures temperature.

*Temperature is measured in units called degrees.  Two temperature scales are the Celsius scale and the Fahrenheit scale.

*Heat is thermal energy that is transferred from a hotter object to a cooler one.

*Heat is transferred in three ways: convection, conduction, and radiation.

*Atoms and molecules in fluids (liquids and gases) can move easily.  As they move, their energy moves with them.

*The transfer of heat by the movement of a fluid is called convection.

*The transfer of heat between two substances that are in direct contact (touching) is called conduction.

*When a fast moving molecule bumps into a slower moving molecule, the faster one transfers some of its energy to the slower one.

*The closer the molecules are in a substance, the better they conduct heat.  Conduction works best in some solids, such as metals, but not as well in liquids and gases.

*Radiation is the direct transfer of energy by electromagnetic waves.  Most of the heat you feel from the sun travels to you as infrared radiation, which you cannot see but can feel.

*Radiation, conduction, and convection work together to heat the troposphere.  During a sunny day the land gets warmer than the air.  But because air doesn’t conduct heat well, only the first few meters of the troposphere are heated by conduction.

*When air at ground level warms, its molecules spread out, making it less dense.  Cooler dense air sinks toward the surface, forcing the warmer air to rise.  The upward movement of warm air and the downward movement of cool air form convection currents.

*Heat is transferred mostly by convection within the troposphere.

Chapter 5, Lesson 2 Notes

*The water cycle is the continuous process by which water moves from Earth’s surface to the atmosphere and back, driven by gravity and energy from the sun.

*In the water cycle, water moves between land, living things, bodies of water on Earth’s surface, and the atmosphere.

*Processes included in the water cycle are evaporation, the process where molecules at the surface of a liquid absorb enough energy to change to a gaseous state, and transpiration, the process of water taken in by plants and given off through the leaves as water vapor.

*Water vapor in the air cools and condenses into liquid water, which eventually forms clouds.  When the water droplets become heavy, they fall back to Earth as rain, snow, hail, or sleet, all of which are forms of precipitation.

Chapter 5, Lesson 3 Notes

*Weather changes every day.  Across a local area beachgoers may enjoy a cool day while those living inland may find temperatures higher.

*Temperature is affected by latitude, altitude, distance from large bodies of water, and ocean currents.

*In general, areas near the equator have warmer climates than areas far from the equator because the sun’s rays hit Earth’s surface more directly at the equator than at the poles.

*The tropical zone is the area near the equator, between about 23.5 degrees north latitude and 23.5 degrees south latitude.

*Polar zones extend from about 66.5 degrees to 90 degrees north and 66.5 degrees to 90 degrees south latitudes.

*Between the tropical zones and the polar zones are temperate zones.

*Many mountainous areas have cooler climates than the lower areas around them.  In the case of high mountains, altitude is a more important factor than latitude.

*Oceans or large lakes can make temperatures on nearby land less extreme.  Much of the west coasts of North America, South America, and Europe have relatively mild winters and cool summers.

*Coastal areas are influenced by the regular patterns of ocean currents.  Some warm ocean currents move from the tropics toward the poles, warming the air above the water and nearby land.

*Some cold currents move from the polar zones towards the equator, cooling the air and nearby land.

*However, the centers of North America and Asia are too far inland to be warmed or cooled by the ocean.  Most of Canada, Russia, and the central United States reach more extreme temperatures than coastal areas.

*Over time, total precipitation in an area tends toward a yearly average.

*The main factors that affect precipitation are prevailing winds, the presence of mountains, jet streams, and seasonal winds.

*Weather patterns depend on the movement of huge air masses.

*Prevailing winds are those that usually blow in one direction in a region.

*The amount of precipitation that might fall depends on where the winds blow from.

*A mountain range in the path of prevailing winds can influence where precipitation falls.

*Rain or snow falls on the windward side of the mountains, the side the wind hits.

*Little precipitation falls on the land on the leeward side of the mountains-the side the wind does not hit.

*Narrow bands of high-speed winds called jet streams, travel far above Earth’s surface.  They blow from east to west along the boundary of warm and cold air masses.  The jet streams can bring warm or cold air across a region and intensify storms.

*In some parts of the world, a seasonal change in wind patterns affects precipitation.

*Sea and land breezes over a large region that change direction with the seasons are called monsoons.


Chapter 5, Lesson 4 Notes

*Air is made up of atoms and molecules, which have mass.

*Because air has mass, it also has other properties, including density and pressure.

*The amount of mass in a given volume of air is its density.

*You calculate the density of a substance by dividing its mass by its volume.

*The force pushing on an area or surface is called pressure.

*Air pressure is the result of the weight of a column of air pushing on an area.

*The reason air pressure does not crush you is because the molecules in air push in all directions. So the air pushing down is balanced by the air pushing up.

*Air pressure can change daily.  A barometer is an instrument that is used to measure air pressure.

*The two common kinds of barometers are mercury barometers and aneroid barometers.

*A mercury barometer consists of a long glass tube that is closed at one end and open at the other.  The open end rests in a dish of mercury.  The closed end contains very little air.  Increases in air pressure force the column of mercury higher in the tube.  The level of mercury in the tube shows the pressure of the air that day.  An aneroid barometer has an airtight metal chamber.  When air pressure increases, the thin walls of the chamber are pushed in.  When air pressure drops, the walls bulge out.  As the chamber’s shape changes a needle on the dial moves.. Weather reports air pressure in inches of mercury.  National Weather Service maps indicate air pressure in millibars. One inch of mercury equals about 33.86 millibars.

Altitude, or elevation, is distance above sea level.  Air pressure decreases as altitude increases.  As air pressure decreases, so does density.  Because air is less dense at a high altitude, each cubic meter of air you breathe has fewer oxygen molecules that at sea level.. So you would become short of breath more quickly at a high altitude.

Chapter 5, Lesson 5 Notes

*Differences in air pressure cause the air to move.

*A wind is the movement of air parallel to Earth’s surface.  Winds move from areas of high pressure to areas of lower pressure.

*Most differences in air pressure are caused by the unequal heating of the atmosphere.

*As air over heated surfaces expands and becomes less dense, its air pressure decreases.

*If nearby air is cooler, it will flow under the warmer, less dense air.

*Winds are described by their direction, determined with a wind vane, and speed, measured with an anemometer.

*A wind is named for the direction it blows from.

*Winds that blow over short distances are called local winds.  They are caused by the unequal heating of Earth’s surface within a small area.

*Local winds form only when large-scale winds are weak.

*Two types of local winds are sea breezes and land breezes.

*A sea breeze is a local wind that blows from an ocean.  During the day, land warms faster than water.  The air above the land heats and rises, and cool air from the ocean flows in to take its place.

*At night the process is reversed, land cools faster than the ocean.  The flow of air from land to a body of water forms a land breeze.

Chapter 5, Lesson 6 Notes

*Humidity is a measure of the amount of water vapor in the air.

*The ability of air to hold water vapor depends on the air’s temperature.

*Warm air can hold more water vapor than cool air.

*Relative humidity is the percentage of water vapor in the air as compared to the maximum amount of water vapor the air can hold at a particular temperature.  For example, at 10 degrees Celsius, 1 cubic meter of air can hold at most 8 grams of water vapor.

*If the air had 4 grams of water vapor, the relative humidity would be 50%.

*Relative humidity can be measured with an instrument called a psychrometer.

*A psychrometer has two thermometers, a wet-bulb thermometer, which is covered by a moist cloth, and a dry-bulb thermometer.

*When the psychrometer is “slung”, or spun, air blows over both thermometers.  Because the wet-bulb thermometer is cooled by evaporation, its reading drops.

*The relative humidity can be found by comparing the temperatures of the wet-bulb and dry-bulb thermometers.

Get 2 Months for $5!