Agenda : Water in the Air - Water Cycle - Humidity - Condensation - Dew Point Lab TN STANDARD: Analyze and interpret data from weather conditions, weather maps, satellites, and radar to predict probable local weather patterns and conditions.

SOMEONE SAW A SNOWFLAKE IN PORTLAND!

What is Weather? How does weather affect your daily life? The condition of the atmosphere at a certain time and place. Affected by amount of water in the air To understand weather, you need to understand how water cycles through Earth’s atmosphere.

THE WATER CYCLE For millions of years, WATER in whatever form, is constantly being recycled through the water cycle. The water cycle is the continuous movement of water from sources on Earth’s surface - such as lakes, oceans and plants - into the air, onto and over land, into the ground, and back to the surface. Can you name the 4 stages of the water cycle?

THE WATER CYCLE Evaporation occurs when liquid water changes into water vapor, which is a gas. Condensation occurs when water vapor cools and changes from a gas to a liquid. Clouds form by this process. Precipitation occurs when the rain, snow, sleet, or hail falls from the clouds onto Earth’s surface. Runoff is water, usually from precipitation, that flows across land and collects in rivers, streams, and eventually the ocean.

What is the water cycle? Rain bump another neighbor to answer…

HUMIDITY As water evaporates from lakes, oceans and plants, it becomes water vapor - invisible moisture in the air The amount of water vapor in the air is humidity As water evaporates & becomes water vapor, humidity increases As temperature of air increases, air’s ability to hold water vapor increases

RELATIVE HUMIDITY Relative humidity - the amount of water vapor in the air compared with the maximum amount of water vapor that the air can hold at a certain temperature Relative humidity is given as a percentage When air holds all the water that it can at a given temperature, it is said to be saturated Saturated air has a relative humidity of 100% Two factors that affect relative humidity are: amount of water vapor and temperature

MEASURING RELATIVE HUMIDITY A psychrometer is an instrument that is used to measure relative humidity. Consists of two thermometers: 1. wet-bulb thermometer - covered with a damp cloth 2. dry-bulb thermometer Difference in temperature readings between the 2 thermometers indicates the amount of water vapor in the air.

CONDENSATION Have you ever seen water droplets form on the outside of a glass of ice water? Where did those water droplets come from? The water came from the surrounding air, and droplets formed as a result of condensation. Condensation is the process by which a gas, such as water vapor, becomes a liquid. The air has to be saturated before condensation can occur. Thinking back to relative humidity, do you remember what the % must be for saturation take place?

DEW POINT Before Condensation can occur, the air must be saturated, which means that the air must have a relative humidity of 100% Condensation occurs when saturated air cools Air can become saturated when water vapor is added to the air through evaporation. Air can also become saturated when it cools to its dew point The dew point is the temperature at which a gas condenses into a liquid The ice in the glass of water causes the air surrounding the glass to cool to its dew point Before water vapor can condense, it must have a surface to condense on like the outside of the glass

Answer the following questions What is weather? What are the 4 stages of the water cycle? Humidity is the amount of _____________in the air. When the temperature of the air cools to its___________, the air has reached saturation & condensation occurs.

Dew Point & Relative Humidity https://www.youtube.com/watch?v=-i9s4bdVMdE Study Jams water cycle https://www.youtube.com/watch?v=z5G4NCwWUxY Crash Course Kids https://www.youtube.com/watch?v=CL5cgXwKUXc Teacher demo Meteorologist Dew Point https://www.youtube.com/watch?v=S8W-xl4mcJ8 https://www.youtube.com/watch?v=0nS5c7qKfhQ https://www.youtube.com/watch?v=OiejHVHrdOo&t=67s Storm Shield Dewpoint Dewpoint illustration STANDARD: Interpret meteorological data to make predictions about the weather

Dew you get the Point? Dew Point Lab Choose a Lab partner to share materials and complete lab sheet You will need: Lab sheet (one for each partner) Tin can filled halfway with tap water Glass thermometer Apron for each person Cup of ice cubes Stopwatch

Directions – Experiment #1 We are measuring the dew point, which is the temperature the AIR must be cooled for the water vapor to condense to a liquid. We will determine the dew point of the air in our classroom. Fill can halfway with tap water Record temperature of water in can Record ROOM TEMPERATURE on wall thermostat Observe the sides of the can, brush finger lightly across checking for moisture PREDICT: Based on the water’s temperature, what degree do you think the air has to be cooled to form condensation? How long do you think this process will take? Starting stopwatch, slowly add several ice cubes. Stir gently Observe evidence of moisture forming on outside of can Brush finger lightly across to check. Record temperature and time DEW POINT occurred

Directions - Experiment #2 Empty can, rinse and fill again halfway with tap water Refill supply of ice if needed Record temperature of water in can Place can near portable heater and record temperature of area near heater Repeat previous steps: Predict time and temperature of dew point (water vapor beside can will condense to a liquid) Slowly add ice cubes, observing evidence of moisture on side of can Record time and dew point temperature

Conclusion What was the independent variable in our experiments? What was the dependent variable? How did the heat affect outcome? Was the dewpoint different for each experiment or the same? Were your predictions correct? MAKE SURE YOUR INFO IS COMPLETE AND BOTH PARTNERS NAMES ARE ON THE LAB SHEET