Vocabulary for this unit:
Water is a liquid. Liquids take up a definite volume but do not have a fixed shape. You can pour water into glasses of different shapes and it will take the shape of each glass. (S4E3a)
When water is ice, it is a solid. Solids have a definite volume and shape. Their volume and shape cannot be easily changed. Water that is colder than 32°F (32 degrees Fahrenheit) or 0°C (0 degrees Celsius) turns into solid ice. (S4E3a, b)
When water is a gas it is called a vapor. Gases have no definite volume and take the shape of their container. Liquid water turns into steam at 212°F or 100°C. (S4E3a, b)
The water cycle is the process that moves water above, below, and around Earth in a cycle. The water cycle has four main stages: evaporation, condensation, precipitation, and collection.
Evaporation happens when the Sun heats up liquid water and causes it to evaporate.
The water vapor, which is a gas, then rises up into the atmosphere. Water vapor forms clouds as it cools.
This cooling is known as condensation. The clouds then release the water as precipitation, in the form of rain, snow, sleet and freezing rain, and hail. As the water runs off, it is collected into the ground and bodies of water. The Sun then heats the liquid water up, causing it to evaporate, and the water cycle starts all over again. (S4E3d)
Clouds form when moist, warm air cools and expands. The water vapor in the air condenses to form small water droplets. Once the air reaches a point of saturation (a point at which there is too much water vapor in the air), clouds begin to form. Small particles of dust in the atmosphere help this process of condensation as water droplets congregate around them. (S4E3c)
Rain is liquid water that falls from the sky as drops. The water vapor in a cloud condenses and turns into liquid water in the form of rain. (S4E3e) Snow is solid water that falls from the sky. It can take many forms depending on the temperature and humidity in the atmosphere. Snow is formed when a little drop of water freezes in a cloud. More water slowly freezes around the ice drop. This is why snowflakes have their shapes. (S4E3e)
Sleet is solid water that falls from the sky. Sleet is pellets of ice. Sleet is formed when a little drop of water freezes in a cloud. More water slowly freezes around the ice drop. The snowflake then gets lifted up into a warmer part of the cloud. The arms of the snowflake then melt. As this melting ice drop falls through the cold part of the cloud, the water from the arms then refreezes in a new ice layer around the original center, it turns into a larger drop of ice. (S4E3e)
Hail is solid water that falls from the sky as ice. Hail is made up of groups of little balls of ice. Hail forms during thunderstorms. Hail starts out as a small ball of ice. As it falls through the tall clouds, more water freezes to it. When it reaches the ground, hail can be as small as a pea or as large as a softball. (S4E3e)
Dew is liquid water that forms on objects outside in the morning or evening. Water vapor in the air condenses on the objects, like car windows and grass. Dew is a form of condensation. (S4E3e)
Fog is water vapor that hangs in the air near the surface of Earth. When the air gets cool enough, the water vapor in the air forms bigger droplets. These are the same kind of droplets that clouds have. This is why fog is considered a cloud that has settled on the ground. (S4E3e)
Meteorologists are scientists who study weather. Meteorologists use many different kinds of tools to help them observe the weather. (S4E4a)
A thermometer is a tool used to measure temperature. Temperature is a measure of the heat energy contained in an object. In other words, temperature is a measure of how hot or cold something is. A thermometer is used to tell the temperature inside or outside. (S4E4a)
A rain gauge is used to collect and measure the amount of rain that falls. Rain gauges are put outside. They are put in areas away from buildings and trees. (S4E4a)
A wind vane is also known as a weather vane. Wind vanes show the direction the wind is blowing. They are often put on the tops of barns and houses. (S4E4a)
An anemometer is a tool that measure how fast the wind is blowing. Some anemometers look like a wind vane. An anemometer has three or four cups connected to a shaft. The cups catch the wind and turn the shaft. You can count the number of times the shaft turns to find out the wind speed. (S4E4a)
When people talk about weather, they are talking about the conditions in the atmosphere at a specific time. Conditions that describe the weather include the temperature, humidity, and amount of wind. For example, the temperature in Georgia on January 5 was 41°F. This is an example of the weather of Georgia. (S4E4d)
When people talk about climate, they talk about the average of weather conditions in an area over a long time. To compare the two, think about the temperature. The average temperature in Georgia is about 39°F in January. This is an example of the climate of Georgia. (S4E4d)
A weather map shows the weather conditions in an area. There are weather symbols on the map. Snow is shown as a snowflake. Rain is shown as drops of water. Sunny weather is shown as a Sun. A weather map can show just one state, such as Georgia, or a larger area, such as the United States. (S4E4b)
Areas where two different air masses meet are called weather fronts. On a black-and white weather map, warm fronts have filled-in half circle symbols placed at intervals on the side of the arc facing the direction the front is moving. Cold fronts have filled-in triangular "sawtooth" symbols at intervals on the side of the arc facing the direction the front is moving. Color weather maps may also show warm fronts as red and cold fronts as blue. Cold fronts often move into an area where a warm front was present. (S4E4b)
Humidity is the amount of water vapor that is in the air. When it is humid, rain, dew, or fog is more likely to occur. (S4E4b)
Meteorologists often talk about high and low pressure systems when they talk about weather. A low pressure system forms when warm and moist air rises, due to Earth’s rotation and friction. This air is pushed toward the center of the system, leading to condensation and precipitation. In a high pressure system, air moves away from the center and the warm air is pushed down. This causes clouds to break up and makes for sunnier weather. (S4E4b)
A barometer is a tool that is used to show and measure the change in air pressure. If the air pressure stays the same, the weather will usually stay the same. When the air pressure goes up a lot or goes down a lot, the weather will change. (S4E4a, c)
Water is a liquid. Liquids take up a definite volume but do not have a fixed shape. You can pour water into glasses of different shapes and it will take the shape of each glass. (S4E3a)
When water is ice, it is a solid. Solids have a definite volume and shape. Their volume and shape cannot be easily changed. Water that is colder than 32°F (32 degrees Fahrenheit) or 0°C (0 degrees Celsius) turns into solid ice. (S4E3a, b)
When water is a gas it is called a vapor. Gases have no definite volume and take the shape of their container. Liquid water turns into steam at 212°F or 100°C. (S4E3a, b)
The water cycle is the process that moves water above, below, and around Earth in a cycle. The water cycle has four main stages: evaporation, condensation, precipitation, and collection.
Evaporation happens when the Sun heats up liquid water and causes it to evaporate.
The water vapor, which is a gas, then rises up into the atmosphere. Water vapor forms clouds as it cools.
This cooling is known as condensation. The clouds then release the water as precipitation, in the form of rain, snow, sleet and freezing rain, and hail. As the water runs off, it is collected into the ground and bodies of water. The Sun then heats the liquid water up, causing it to evaporate, and the water cycle starts all over again. (S4E3d)
Clouds form when moist, warm air cools and expands. The water vapor in the air condenses to form small water droplets. Once the air reaches a point of saturation (a point at which there is too much water vapor in the air), clouds begin to form. Small particles of dust in the atmosphere help this process of condensation as water droplets congregate around them. (S4E3c)
Rain is liquid water that falls from the sky as drops. The water vapor in a cloud condenses and turns into liquid water in the form of rain. (S4E3e) Snow is solid water that falls from the sky. It can take many forms depending on the temperature and humidity in the atmosphere. Snow is formed when a little drop of water freezes in a cloud. More water slowly freezes around the ice drop. This is why snowflakes have their shapes. (S4E3e)
Sleet is solid water that falls from the sky. Sleet is pellets of ice. Sleet is formed when a little drop of water freezes in a cloud. More water slowly freezes around the ice drop. The snowflake then gets lifted up into a warmer part of the cloud. The arms of the snowflake then melt. As this melting ice drop falls through the cold part of the cloud, the water from the arms then refreezes in a new ice layer around the original center, it turns into a larger drop of ice. (S4E3e)
Hail is solid water that falls from the sky as ice. Hail is made up of groups of little balls of ice. Hail forms during thunderstorms. Hail starts out as a small ball of ice. As it falls through the tall clouds, more water freezes to it. When it reaches the ground, hail can be as small as a pea or as large as a softball. (S4E3e)
Dew is liquid water that forms on objects outside in the morning or evening. Water vapor in the air condenses on the objects, like car windows and grass. Dew is a form of condensation. (S4E3e)
Fog is water vapor that hangs in the air near the surface of Earth. When the air gets cool enough, the water vapor in the air forms bigger droplets. These are the same kind of droplets that clouds have. This is why fog is considered a cloud that has settled on the ground. (S4E3e)
Meteorologists are scientists who study weather. Meteorologists use many different kinds of tools to help them observe the weather. (S4E4a)
A thermometer is a tool used to measure temperature. Temperature is a measure of the heat energy contained in an object. In other words, temperature is a measure of how hot or cold something is. A thermometer is used to tell the temperature inside or outside. (S4E4a)
A rain gauge is used to collect and measure the amount of rain that falls. Rain gauges are put outside. They are put in areas away from buildings and trees. (S4E4a)
A wind vane is also known as a weather vane. Wind vanes show the direction the wind is blowing. They are often put on the tops of barns and houses. (S4E4a)
An anemometer is a tool that measure how fast the wind is blowing. Some anemometers look like a wind vane. An anemometer has three or four cups connected to a shaft. The cups catch the wind and turn the shaft. You can count the number of times the shaft turns to find out the wind speed. (S4E4a)
When people talk about weather, they are talking about the conditions in the atmosphere at a specific time. Conditions that describe the weather include the temperature, humidity, and amount of wind. For example, the temperature in Georgia on January 5 was 41°F. This is an example of the weather of Georgia. (S4E4d)
When people talk about climate, they talk about the average of weather conditions in an area over a long time. To compare the two, think about the temperature. The average temperature in Georgia is about 39°F in January. This is an example of the climate of Georgia. (S4E4d)
A weather map shows the weather conditions in an area. There are weather symbols on the map. Snow is shown as a snowflake. Rain is shown as drops of water. Sunny weather is shown as a Sun. A weather map can show just one state, such as Georgia, or a larger area, such as the United States. (S4E4b)
Areas where two different air masses meet are called weather fronts. On a black-and white weather map, warm fronts have filled-in half circle symbols placed at intervals on the side of the arc facing the direction the front is moving. Cold fronts have filled-in triangular "sawtooth" symbols at intervals on the side of the arc facing the direction the front is moving. Color weather maps may also show warm fronts as red and cold fronts as blue. Cold fronts often move into an area where a warm front was present. (S4E4b)
Humidity is the amount of water vapor that is in the air. When it is humid, rain, dew, or fog is more likely to occur. (S4E4b)
Meteorologists often talk about high and low pressure systems when they talk about weather. A low pressure system forms when warm and moist air rises, due to Earth’s rotation and friction. This air is pushed toward the center of the system, leading to condensation and precipitation. In a high pressure system, air moves away from the center and the warm air is pushed down. This causes clouds to break up and makes for sunnier weather. (S4E4b)
A barometer is a tool that is used to show and measure the change in air pressure. If the air pressure stays the same, the weather will usually stay the same. When the air pressure goes up a lot or goes down a lot, the weather will change. (S4E4a, c)