MS-ESS2-5NGSS*ScienceEarth and Space ScienceGrades 6-8
MS-ESS2-5: Collecting Data on Air Masses, Fronts and Changing Weather
In plain English: MS-ESS2-5 is the NGSS middle school performance expectation that asks students to collect data as evidence for how moving and colliding air masses change the weather. Students log temperature, pressure, humidity, wind and precipitation, read weather maps, measure dew point and make forecasts with chances. It is usually taught in grade 6, 7 or 8 Earth science.
Collect data to provide evidence for how the motions and complex interactions of air masses result in changes in weather conditions.
Clarification Statement: Emphasis is on how air masses flow from regions of high pressure to low pressure, causing weather (defined by temperature, pressure, humidity, precipitation, and wind) at a fixed location to change over time, and how sudden changes in weather can result when different air masses collide. Emphasis is on how weather can be predicted within probabilistic ranges. Examples of data can be provided to students (such as weather maps, diagrams, and visualizations) or obtained through laboratory experiments (such as with condensation).
Assessment Boundary: Assessment does not include recalling the names of cloud types or weather symbols used on weather maps or the reported diagrams from weather stations.
Next Generation Science Standards · Disciplinary Core Idea: Earth's Systems · Official standard
Students collect and analyze weather data to explain why the weather at one place changes from day to day and sometimes within an hour. Weather is the condition of the air at a place and time, described by five variables: temperature, air pressure, humidity (the amount of water vapor in the air), precipitation and wind. An air mass is a huge body of air, often more than 1,000 km across, with about the same temperature and humidity throughout; it takes on the properties of the land or sea where it formed. Air moves from areas of high pressure toward areas of low pressure, so air masses travel, and where two meet, the boundary between them is a front. Students log weather data, measure the dew point in a lab, model colliding air masses in a water tank, read an invented weather map and make forecasts that give chances, not certainties.
The NGSS Clarification Statement says: "Emphasis is on how air masses flow from regions of high pressure to low pressure, causing weather (defined by temperature, pressure, humidity, precipitation, and wind) at a fixed location to change over time, and how sudden changes in weather can result when different air masses collide. Emphasis is on how weather can be predicted within probabilistic ranges. Examples of data can be provided to students (such as weather maps, diagrams, and visualizations) or obtained through laboratory experiments (such as with condensation)." The Assessment Boundary says: "Assessment does not include recalling the names of cloud types or weather symbols used on weather maps or the reported diagrams from weather stations." So this page describes clouds in plain words, labels fronts and towns in words, and never asks students to name a cloud type or a map symbol. All data sets are invented for teaching. Safety: only the teacher handles warm water.
Learning Objectives
By the end of this lesson, students will be able to:
Collect and organize weather data (temperature, pressure, humidity, precipitation and wind) at one location over time
Use pressure data to explain that air moves from high pressure toward low pressure
Use data from a weather log, a weather map or a lab to identify when a front passed and which air mass replaced which
Measure the dew point with a condensation lab and use it to compare the humidity of two air masses
Make a weather forecast with a range or a chance, and judge a forecast with data from many days
Prior Knowledge Required
Students should already be comfortable with:
Condensation and evaporation in the water cycle MS-ESS2-4
Recording weather data in tables and graphs 3-ESS2-1
The probability of a chance event is a number from 0 to 1, or 0% to 100% 7.SP.C.5
Warmer matter takes up more space, so warm air is less dense than cold air
Show a two-day forecast for an invented town: "Tuesday: high 24 °C, muggy, wind from the south. Line of thunderstorms in the evening. Wednesday: high 11 °C, dry, wind from the northwest, 10% chance of rain."
Warm-Up Prompt
"The high temperature drops 13 °C in one day. Where did Tuesday's warm, muggy air go, and where did Wednesday's air come from? What could you measure at school on both days to find out?"
List students' measurement ideas on the board. Many will say temperature; push for the other four variables: pressure, humidity, wind and precipitation. Ask what "10% chance of rain" means; keep the answers on the board for Direct Instruction.
Direct Instruction15 minutes
Key words.Air pressure is the push of the air above on each square meter; a barometer measures it, here in hPa (hectopascals). At sea level it is usually between about 980 and 1040 hPa. Air moves from high pressure toward low pressure, and that moving air is wind. Wind is named for the direction it comes from: a south wind blows from the south. In a low, air rises, cools and forms clouds; in a high, air sinks and skies are usually clear. The dew point is the temperature to which air must cool for its water vapor to start condensing; a higher dew point means more water vapor. A cold front is where cold air pushes into warm air, and a warm front is where warm air moves into colder air.
Forecasts with chances. A forecast such as "30% chance of rain" is a probability: it gives the chance that a measurable amount of rain falls at a given spot during the time period. Forecasts also give ranges, such as "a high of 18-22 °C", because air masses move and interact in complex ways that nobody can measure perfectly. Use Diagram 1 to show highs, lows, two fronts and the air masses around them, and Diagram 2 to show the side view of a cold front.
Pressure difference and wind
At noon, Town M reads 1020 hPa and Town N, 300 km to the east, reads 1008 hPa.
Result: The difference is 12 hPa over 300 km, or 4 hPa per 100 km. Air moves from Town M (high) toward Town N (low), so Town N gets a west wind. A larger difference over the same distance gives a stronger wind. (Earth's rotation also turns the wind to one side, which is part of MS-ESS2-6.)
Where air masses come from
In January, air that has sat for a week over snow-covered northern Canada is at -18 °C with a dew point of -24 °C. Air over the Gulf of Mexico is at 22 °C with a dew point of 18 °C.
Result: Each air mass took on the temperature and humidity of the surface below it: cold and dry over snow, warm and humid over warm water. When the two meet over the middle of North America, the 40 °C contrast makes a strong front.
A cold front passes (data)
At 2 p.m. a town reads 29 °C, dew point 22 °C, wind from the south, 1004 hPa. A line of storms passes at 4 p.m. with 15 mm of rain in 30 minutes. At 6 p.m. it reads 18 °C, dew point 10 °C, wind from the northwest, 1010 hPa.
Result: Temperature -11 °C, dew point -12 °C, pressure +6 hPa, and the wind turns from south to northwest. Every variable changed within a few hours: cold, dry air pushed in under the warm, humid air and lifted it, making short, heavy rain.
A warm front passes (data)
Over 12 hours, light rain falls (6 mm in all), the temperature rises from 7 °C to 15 °C, the dew point rises from 5 °C to 13 °C, and the wind turns from east to south.
Result: Temperature +8 °C and dew point +8 °C: warmer, more humid air replaced the cool air. At a warm front the warm air slides up gently over the cold air, so the rain is light and lasts many hours.
Checking a forecast with data
A TV station forecast a "30% chance of rain" on 40 different days. Rain fell on 13 of those days.
Result: 13 ÷ 40 = 0.325 = 32.5%, close to 30%. The station's 30% forecasts match what happened on those 40 days.
After each example, ask: "Which of the five weather variables changed, by how much, and what does that tell you about the air over the town?"
Guided Practice10-15 minutes
Pairs graph the invented readings below from a school weather station on one afternoon. They put time on the horizontal axis and draw temperature and dew point on one graph and pressure on a second graph, a visualization of the data.
Guided practice data (invented): readings every 2 hours at a school
Time
Temperature (°C)
Dew point (°C)
Pressure (hPa)
Wind from
Rain in the last 2 hours (mm)
10:00
25
20
1008
S
0
12:00
27
21
1006
S
0
14:00
27
21
1004
SW
2
16:00
19
13
1007
NW
14
18:00
16
9
1010
NW
0
20:00
15
8
1012
NW
0
Find the time of the lowest pressure. What happens to the pressure after that?
Find the 2-hour period with the largest temperature drop. Did the dew point drop at the same time?
Mark on both graphs when you think the front passed. Which kind of front was it? List evidence from four of the five variables.
Describe the air mass before and after the front in one sentence each.
Debrief: the pressure is lowest at 14:00 and then rises. Between 14:00 and 16:00 the temperature falls 8 °C, the dew point falls 8 °C, the wind turns to the northwest and 14 mm of rain falls, so a cold front passed. Warm, humid air was replaced by cooler, drier air.
Independent Practice10-15 minutes
Each student uses Diagram 1, the invented weather map, to write a forecast for Town D for the next 24 hours. In this map, both fronts are moving east, and the warm front is also moving north toward Town D.
Describe the air mass Town D is in now, using its temperature, wind and weather.
Predict how Town D's temperature, dew point, wind direction and precipitation will change when the warm front passes. Give each prediction as a direction (rise, fall, stay about the same).
Give a range for tomorrow's high temperature and a chance of rain, and explain why you used a range and a chance.
Name two measurements Town D could collect tomorrow to check your forecast.
Collect the forecasts and keep them: in Closure, students compare their forecasts with a partner's and explain one difference.
Closure5 minutes
Exit ticket: "Name one weather variable that changes a lot at night even when the air mass stays the same, and one that changes much less. Which one is better evidence that a new air mass arrived, and why?" Then return to the warm-up and ask students to rewrite their explanation of the 13 °C drop using the words air mass and front.
Differentiation Strategies
For Struggling Students
Give a graph with the axes and scales already drawn, and have students plot only temperature first
Use a "before the front / after the front" two-column table so students compare one variable at a time
Provide a sentence frame: "Between ___ and ___, the temperature ___ by ___ and the wind changed from ___ to ___, so a ___ front passed."
For Advanced Students
Ask students to estimate how fast a front moved from the times it passed two towns a known distance apart
Have students compare a week of forecasts with what really happened and compute how often each stated chance matched the outcome
Ask students to explain why a front over the ocean can bring fog to a coast, using the dew point
Assessment Guidance
What to Look For
Check that students use several variables, not only temperature, as evidence that an air mass changed, and that they read wind as the direction it comes from. Look for students who think relative humidity or a "chance of rain" is the amount of rain. Listen for the idea that air moves from high to low pressure, and for forecasts written as ranges and chances. Students should not be asked to name cloud types or map symbols.
02
Classroom Activities
3 Activities
1
Dew Point Lab: Measuring the Water Vapor in an Air Mass
20 minPairs
Pairs measure the dew point of the outdoor air by cooling a shiny metal cup of water until droplets condense on the outside. They repeat the lab on two days, before and after a front, and use the dew points as evidence about the air masses.
Procedure
Work outdoors in the shade, or by an open window. Fill a dry, shiny stainless steel cup halfway with tap water and put a digital or alcohol thermometer in it. Record the air temperature with a second thermometer in the shade.
Add one ice cube at a time and stir gently with the thermometer. Watch the outside of the cup closely.
Record the water temperature the moment a thin fog of droplets appears on the outside. That is the dew point. Dry the cup, let it warm up, and repeat for three trials.
Repeat the lab at the same time of day after the weather changes.
Safety: never use a mercury thermometer, report broken thermometers to the teacher, and wipe up spilled water so no one slips.
Sample Data (invented)
Day 1, before a front: air temperature 26 °C, dew point trials 19.5, 20.0 and 19.0 °C. Day 2, after the front: air temperature 17 °C, dew point trials 6.0, 5.5 and 6.5 °C.
Discussion Questions
Find the mean dew point for each day. On which day did the air hold more water vapor?
The air temperature fell 9 °C from Day 1 to Day 2. Did the dew point fall by more or by less? What does that tell you about the air?
Why do you think the lab asks for three trials and a reading in the shade?
Which kind of front could explain the change between the two days? What other data would you want to collect to check?
Modification for Distance Learning
Students do the lab at home with a metal cup or a clean steel can with no sharp edges, ice and a kitchen thermometer, or use the sample data, then post their means and claim.
2
Collision Tank: Modeling Two Air Masses Meeting
25 minGroups of 3-4
Groups model two air masses with water of two temperatures in a clear plastic box split by a cardboard divider. When they lift the divider, they watch and time how the two "air masses" move. Water stands in for air because it is easy to see and moves slowly enough to time.
Procedure
Slide a cardboard divider, wrapped in plastic, into the middle of a clear plastic storage box (about 60 cm long). Tape a ruler along the outside of the box.
The teacher pours warm tap water (checked below about 45 °C) with red food coloring into one half. Students pour ice water with blue food coloring into the other half to the same depth, about 10 cm. Record both temperatures.
Lift the divider straight up in one smooth motion. Start a stopwatch and time how long the front edge of the blue water takes to travel 30 cm.
Draw what you see from the side at 5, 10 and 20 seconds.
Empty the box and repeat with ice water and room-temperature water.
Safety: only the teacher pours warm water; wipe spills at once, and keep the box on a low, steady table.
Sample Data (invented)
Trial 1: blue water 5 °C, red water 40 °C. The blue water slid along the bottom and the red water flowed back over the top; the blue edge traveled 30 cm in 9 s. Trial 2: blue water 5 °C, red water 22 °C; the blue edge traveled 30 cm in 18 s.
Discussion Questions
Find the speed of the blue edge in each trial, in cm per second. In which trial was the temperature difference larger?
Which part of the model stands for a cold air mass, and which part stands for a front? Where does the warm water end up, and why?
Compare your side-view drawings with Diagram 2. What does the tank show well about a cold front, and what does it leave out (for example, water vapor and clouds)?
Modification for Distance Learning
Students watch a teacher-recorded video of the tank, step through it frame by frame to time the blue edge, and post their speeds and a labeled side-view drawing.
3
Five-Day Weather Log and Forecast
15 min a day for 5 days, plus 25 min to analyzeGroups of 3-4
Groups collect weather data at the same place and time each school day for a week, then use the log as evidence of which air masses passed over the school. They finish by forecasting the next day with a range and a chance, and checking it.
Procedure
Each day at 1 p.m., record the temperature in the shade, the dew point (Activity 1 method or a hygrometer, an instrument that measures humidity), the pressure from the barometer or the school weather station, the wind direction from a ribbon on a stick and a compass, the rain in the gauge since yesterday, and a short description of the sky in your own words.
Each day, also look at a weather map or a radar visualization from the National Weather Service, and note where the nearest front is.
On day 5, graph all five variables and mark the days when you think a front passed.
Sample Data (invented)
Monday: 14 °C, dew point 4 °C, 1021 hPa, wind from N, clear, no rain. Tuesday: 16 °C, dew point 7 °C, 1015 hPa, wind from E, thin high clouds turning gray, no rain. Wednesday: 18 °C, dew point 15 °C, 1009 hPa, wind from SE, light rain all morning, 9 mm. Thursday: 26 °C, dew point 20 °C, 1005 hPa, wind from S, muggy, storms in the evening, 16 mm. Friday: 15 °C, dew point 6 °C, 1016 hPa, wind from NW, clear, no rain.
Discussion Questions
On which day was the pressure lowest? Which days show the pressure falling, and which show it rising?
Between which two readings did a warm front most likely pass, and between which two did a cold front pass? Give evidence from at least three variables for each.
Write a forecast for Saturday as a range of high temperatures and a chance of rain. What would make you more or less sure?
Modification for Distance Learning
Students log the same variables at home from an outdoor thermometer and a free weather service report for their town, and share the log in a class spreadsheet.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: An Invented Weather Map with Two Air Masses
An invented weather map at noon, labeled in words instead of map symbols. A low-pressure center (998 hPa) has a cold front stretching to the southwest and a warm front stretching to the east, and both fronts are moving east. Cold, dry air lies behind the cold front, warm, humid air lies between the two fronts, and cool air lies north of the warm front. Each town shows its temperature, wind direction, pressure and weather.
Diagram 2: Side View of a Cold Front
A side view (cross-section) of a cold front, not to scale. The wedge of cold, dense air moves to the right along the ground and pushes under the warm, humid air ahead of it. The warm air is forced up steeply, cools, and its water vapor condenses into a tall cloud with rain along the front.
04
Homework Assignment
~30 min
MS-ESS2-5 Homework: Air Masses and Weather Data
Directions: All data are invented for practice. Show calculations with units. When you use data as evidence, name the variable, the values and the change. You do not need to name cloud types or map symbols.
Part 1: Collecting and Organizing Data (Problems 1-3)
A cold front is forecast to pass your school between 1 p.m. and 5 p.m. tomorrow. (a) Plan when and how often you will take readings between 11 a.m. and 7 p.m., and explain your choice. (b) Which three weather variables will give the clearest evidence that the front passed, and what change do you expect in each? (c) Draw the empty data table you would use.
At home, a student does the dew point test three times in the evening and gets 11.5, 12.0 and 11.0 °C. The air temperature is 19 °C, and tonight's forecast low is 9 °C. (a) Find the mean dew point. (b) Predict whether dew or fog will form tonight, and explain using the dew point. (c) Tomorrow a cold, dry air mass with a dew point near -2 °C is expected. How will the dew point test change?
Use Diagram 1. Town A and Town B are less than 350 km apart. (a) Compare their temperature, wind and pressure. (b) Which air mass is each town in? (c) Use the pressures on the map to explain where the air around Town A is moving.
Part 2: Data as Evidence and Forecasts (Problems 4-6)
A town records these readings every 4 hours. At 0:00, 4:00, 8:00, 12:00, 16:00 and 20:00, the temperature is 6, 6, 7, 9, 16 and 17 °C; the dew point is 3, 4, 6, 8, 14 and 15 °C; the pressure is 1012, 1010, 1008, 1007, 1007 and 1008 hPa; the wind is from the E, E, E, SE, S and S; and the rain in each 4-hour period is 0, 1, 3, 2, 0 and 0 mm. (a) How much rain fell in all? (b) Between which two readings did a front pass, and what kind of front was it? (c) Give evidence from four variables. (d) How was the rain different from the rain at a cold front?
A weather office checks two kinds of forecasts. On 60 days it said "30% chance of rain," and rain fell on 17 of them. On 40 days it said "70% chance of rain," and rain fell on 29 of them. (a) Find the percent of days with rain for each kind of forecast. (b) Are the forecasts reliable? Explain. (c) Why can one day of data never show that a 70% forecast was right or wrong?
At 7 a.m., a cold front is 200 km west of a town and moving east at 25 km/h. (a) At what time should the front reach the town? (b) Predict the change in each of the five weather variables as it passes. (c) The forecaster gives the arrival time as "between 2 p.m. and 5 p.m." Why give a range?
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Collecting Data
Plan gives a reading schedule that covers the forecast window, the variables to watch and the expected change in each
Plan is missing the schedule, a variable or the expected changes
Data as Evidence
Uses values and changes from several variables to identify a front or an air mass
Uses only one variable, or gives a claim without values
Calculations
Means, totals, percents and times are correct, with units
Method is right but one value or unit is wrong
Forecasts
Gives forecasts as ranges or chances and explains why
Gives a single certain forecast or no reason
05
Quiz: 20 Questions
Interactive, with answers
Instructions
Use Diagram 1 and Diagram 2 where a question asks for them. All data are invented for practice, pressures are in hPa, and wind is named for the direction it comes from. Your score updates as you answer, and Reset quiz clears everything so you or your students can try again.
Multiple choice: pick an option to check it. Short answer: write your answer, then reveal the model answer.
0 of 20 answered · 0 correct
Question 1 of 20 · Multiple Choice
At noon, the air pressure is 1022 hPa in Town P and 1008 hPa in Town Q, 250 km to the east. Which way does the air near the ground move between the two towns?
Answer: B
Air moves from high pressure toward low pressure, so it flows from Town P (1022 hPa) toward Town Q (1008 hPa). Choice A reverses the direction. Choice C is wrong because air does rise over a low, but air near the ground still flows in from higher pressure to replace it. Choice D is wrong because highs and lows hundreds of kilometers apart are exactly what drives wind.
Question 2 of 20 · Multiple Choice
In 2 hours, a town's temperature falls from 26 °C to 17 °C, the wind changes from the south to the northwest, a short heavy rainstorm passes, and the air pressure, which had been falling, starts to rise. What happened?
Answer: C
A fast temperature drop, a wind shift to the northwest, a short heavy storm and rising pressure together are the signs of a cold front. Choice A would make the temperature rise. Choice B describes air that stays the same, which gives steady weather, not a sudden change. Choice D is wrong because evening cooling is gradual and does not turn the wind or bring a storm.
Question 3 of 20 · Multiple Choice
Steady light rain falls for 10 hours. During that time, the temperature rises from 8 °C to 15 °C and the dew point rises from 6 °C to 13 °C. Which explanation fits the data best?
Answer: A
The rising dew point shows that the air now holds more water vapor, so different, more humid air has arrived, and long, steady light rain fits warm air sliding gently up over cooler air at a warm front. Choice B would make the temperature and dew point fall. Choice C could warm the air but would not raise the dew point by 7 °C or bring 10 hours of rain. Choice D is wrong because a high brings sinking, drier air and clearer skies.
Question 4 of 20 · Multiple Choice
Students add ice to water in a shiny metal cup and stir with a thermometer. When the water reaches 12 °C, a thin fog of droplets appears on the outside of the cup. The air temperature is 20 °C. What does the 12 °C reading measure?
Answer: C
The droplets are water vapor from the air condensing on the cold cup. The temperature at which condensation starts is the dew point of the air. Choice A and choice D are both 0 °C for water, not 12 °C. Choice B is the 20 °C reading, not the 12 °C one.
Question 5 of 20 · Multiple Choice
The same dew point test is done outdoors on two days. On Monday, fog forms on the cup at 17 °C. On Thursday, it forms at 4 °C. What is the best explanation?
Answer: A
A lower dew point means the air holds less water vapor, and a change that large over a few days points to a new, drier air mass, for example behind a cold front. Choice B is wrong because ice in water stays near 0 °C, and the fog point depends on the air, not the ice. Choice C is wrong because gravity does not set the amount of water vapor in the air. Choice D reverses the meaning of a lower dew point.
Question 6 of 20 · Multiple Choice
An air mass sits for a week over the warm Gulf of Mexico in summer, then moves north over land. What will it most likely bring to the towns it reaches?
Answer: D
An air mass takes on the properties of the surface where it formed, and warm water gives warm, humid air. Choices A and C describe air that formed over cold land or sea near the poles. Choice B describes air that formed over a desert, not over water.
Question 7 of 20 · Multiple Choice
The forecast for Saturday says "20% chance of rain." It rains at your house on Saturday afternoon. Which statement is best?
Answer: B
A 20% chance means that on many days like this one, rain falls at a given spot on about 2 out of 10, or 1 in 5, so rain on one of them does not show the forecast was wrong. Choice A treats a low chance as zero. Choice C confuses a chance with a share of the day. Choice D draws a conclusion from one outcome, when a probability forecast can only be checked over many days.
Question 8 of 20 · Multiple Choice
A weather office checks its forecasts. On 50 days it forecast a "40% chance of rain," and rain fell on 21 of those days. On what percent of those days did it rain?
Answer: D
21 ÷ 50 = 0.42 = 42%, close to the 40% forecast. Choice A reads the count of rainy days as a percent. Choice B is 50 - 21 = 29, the number of dry days, read as a percent. Choice C is 29 ÷ 50 = 58%, the percent of dry days.
Question 9 of 20 · Multiple Choice
Look at Diagram 2. What would most likely change if the warm air ahead of the cold front were very dry instead of humid?
Answer: A
Clouds and rain form only when rising air has enough water vapor to condense. With dry warm air, little condenses, but the cold air mass still arrives, so it still gets colder. Choice B is wrong because dry air has less water vapor to make rain. Choice C is wrong because the cold air is still denser and stays near the ground. Choice D is wrong because a cold front can pass with few clouds when the air is dry.
Question 10 of 20 · Multiple Choice
A student wants evidence that a new air mass arrived overnight, not just the usual cooling at night. Which measurements are the best evidence?
Answer: B
Night cooling lowers the temperature, but the amount of water vapor (the dew point) and the wind direction stay about the same in one air mass, and readings at the same time of day remove the day-night effect. Choice A shows only the normal night cooling. Choice C has nothing to do with the air mass. Choice D is a single observation of the sky that says nothing about the air's temperature or humidity.
Question 11 of 20 · Multiple Choice
A school barometer reads 1014 hPa at 8 a.m. and 1002 hPa at 8 p.m. the same day. What is the best prediction?
Answer: D
The pressure fell 12 hPa in 12 hours, 1 hPa per hour. A fall that fast often means a low and its fronts are coming, and air rising in a low makes clouds and precipitation more likely. Choice A reverses the meaning of falling pressure. Choice C is wrong because 12 hPa in half a day is a large drop. Choice B turns a chance into a certainty and ignores that snow also needs cold air.
Question 12 of 20 · Multiple Choice
On a calm night in a valley, the air temperature is 20 °C at sunset and the dew point is 12 °C. The forecast low for dawn is 11 °C. What do you predict at dawn?
Answer: A
When air cools to its dew point, its water vapor condenses into droplets: dew on the grass or fog in the air. Choice B is wrong because cooling does not remove water vapor until it condenses. Choice C adds a front that the data do not show. Choice D is wrong because frost needs surfaces below 0 °C, and the low is 11 °C.
Question 13 of 20 · Multiple Choice
Look at Diagram 1. Both fronts are moving east. Which town is most likely to get a sudden thunderstorm and a sharp temperature drop in the next few hours?
Answer: C
Town C is in the warm, humid air just east of the cold front, so the front will reach it first. Choice A is already behind the cold front in cold, dry air. Choice B is also in the warm air but farther from the cold front, so its change comes later. Choice D is north of the warm front: it will warm up when that front passes, not cool suddenly.
Question 14 of 20 · Multiple Choice
At 9 a.m., a cold front is 120 km west of a town and moving east at 30 km/h. About when will the front reach the town?
Answer: D
Time = 120 km ÷ 30 km/h = 4 hours, and 9 a.m. + 4 hours = 1:00 p.m. Choice A divides the wrong way: 30 ÷ 120 = 0.25 hours, or 15 minutes. Choice B subtracts the 4 hours, as if the front had already passed. Choice C reads the 4 hours as a clock time.
Question 15 of 20 · Short Answer
Readings at a park (invented): 3 p.m.: 31 °C, dew point 23 °C, wind from SW, 1003 hPa. 5 p.m.: 30 °C, dew point 23 °C, wind from SW, 1001 hPa, tall clouds to the west. 7 p.m.: 21 °C, dew point 14 °C, wind from NW, 1006 hPa, 22 mm of rain in 40 minutes. 9 p.m.: 19 °C, dew point 11 °C, wind from NW, 1009 hPa, clear. (a) What passed, and between which two readings? (b) Give evidence from at least four of the five weather variables.
(a) A cold front passed between 5 p.m. and 7 p.m. (b) Temperature fell 9 °C (30 to 21 °C); the dew point fell 9 °C (23 to 14 °C), so the new air is drier; the pressure was lowest at 5 p.m. (1001 hPa) and then rose 5 hPa; the wind turned from southwest to northwest; and 22 mm of heavy rain fell in a short burst. By 9 p.m. the cold, dry air mass had replaced the warm, humid one.
Question 16 of 20 · Short Answer
A group's weather log says: "Monday: 12 °C, measured at 8 a.m. in the shade. Tuesday: 22 °C, measured at 3 p.m. in direct sun." The group claims that a warm air mass arrived on Tuesday. (a) Give two reasons why these data do not yet support the claim. (b) What should the group change, and which other variable would give better evidence of a new air mass?
(a) The readings were taken at different times of day: afternoons are usually warmer than early mornings in the same air mass. The Tuesday thermometer was in direct sun, which heats it above the air temperature. Either reason alone could explain much of the 10 °C difference. (b) Measure at the same time and in the shade every day, and add the dew point and the wind direction: a big change in both at the same time of day would be better evidence of a new air mass.
Question 17 of 20 · Short Answer
Town P reads 1018 hPa and Town Q, 200 km away, reads 1002 hPa. Town R reads 1010 hPa and Town S, 300 km away, reads 1006 hPa. (a) Find the pressure difference per 100 km for each pair. (b) Between which pair do you expect the stronger wind, and why?
(a) P to Q: 16 hPa ÷ 2 = 8 hPa per 100 km. R to S: 4 hPa ÷ 3 ≈ 1.3 hPa per 100 km. (b) Between P and Q, blowing from P toward Q: a larger pressure difference over each 100 km pushes the air harder from high pressure toward low pressure.
Question 18 of 20 · Short Answer
Explain why a forecast for 7 days from now usually gives a wider temperature range and less certain chances than a forecast for tomorrow.
Model answer: The weather depends on how air masses move and interact, and these motions are complex. Forecasters start from today's measurements, which are never perfect or complete, and small errors grow as the forecast looks further ahead: a front may arrive hours earlier or later, or take a slightly different path. So forecasts for later days need wider ranges and chances closer to the middle, while tomorrow's forecast can be narrower.
Question 19 of 20 · Short Answer
In a collision tank model, blue water at 5 °C and red water at 30 °C are released side by side. The blue edge travels 40 cm along the bottom in 16 s. (a) Find its speed. (b) Predict whether the edge would move faster or slower if the red water were 15 °C, and explain what this part of the model stands for in real air masses.
(a) 40 cm ÷ 16 s = 2.5 cm/s. (b) Slower: with a smaller temperature difference, the two waters are closer in density, so the cold water pushes under the warm water less strongly. In the atmosphere, a front between air masses with a small temperature contrast moves and lifts the warm air less forcefully, and its weather changes are usually milder than those of a front with a strong contrast.
Question 20 of 20 · Short Answer
A forecaster says tomorrow's high will be "between 14 and 22 °C, depending on when the cold front arrives." Explain why the timing changes the high so much, and name two measurements the town could watch in the morning to tell that the front is close.
Model answer: If the front arrives early, the cold air mass replaces the warm air before the afternoon, so the high stays near 14 °C. If it arrives in the evening, the warm air heats up all afternoon and the high reaches about 22 °C. Signs that the front is close: falling pressure on the barometer, tall clouds building to the west, and later a wind shift to the northwest with a drop in dew point.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does MS-ESS2-5 mean?
MS-ESS2-5 asks middle school students to collect data as evidence for how moving and colliding air masses change the weather. Students use measurements of temperature, pressure, humidity, precipitation and wind, plus weather maps and lab data, to explain changes at one place. The code stands for Middle School, Earth and Space Science, core idea 2 (Earth's Systems), performance expectation 5.
What grade is MS-ESS2-5 taught in?
It can be taught in grade 6, 7 or 8: NGSS writes middle school standards for the 6-8 band, and each state or district sets the order. It usually sits in a weather and climate unit, after the water cycle (MS-ESS2-4) and before global circulation and climate (MS-ESS2-6).
What is the assessment boundary for MS-ESS2-5?
Students are not assessed on recalling the names of cloud types or the symbols used on weather maps and station reports. They should be able to read a map that is labeled in words and describe clouds in plain language, but memorizing a symbol key is beyond this standard.
What is an air mass?
An air mass is a very large body of air, often more than 1,000 km across, with about the same temperature and humidity throughout. It gets those properties from the surface where it formed: air over snowy land becomes cold and dry, and air over warm ocean becomes warm and humid. When it moves, it carries that weather with it.
Why does wind blow from high to low pressure?
Air is pushed from where the pressure is higher toward where it is lower, the way air rushes out of a balloon. The bigger the pressure difference over a distance, the stronger the wind. On large scales, Earth's rotation turns the wind to one side, which students meet in MS-ESS2-6.
What weather does a cold front bring?
A cold front often brings a short burst of heavy rain or thunderstorms, then a quick drop in temperature and dew point, a wind shift and rising pressure. The cold air is denser, so it pushes under the warm air and forces it up steeply, as Diagram 2 shows.
What does a percent chance of rain mean?
It is the probability that a measurable amount of rain falls at a given spot in the forecast area during the stated time. Forecasters use chances and ranges because the motions of air masses are complex and every measurement has some error.
What weather data can students collect at school?
With simple tools, students can measure temperature (a thermometer in the shade), pressure (a barometer or a school weather station), humidity (a dew point cup test or a hygrometer), precipitation (a rain gauge) and wind direction (a ribbon and a compass). Readings at the same place and time each day make the data fair to compare.
How does a condensation lab connect to air masses?
The cold-cup lab measures the dew point, which shows how much water vapor the air holds. Because each air mass has its own humidity, the dew point helps tell air masses apart. The same condensation that fogs the cup makes clouds when air rises and cools.
How does MS-ESS2-5 connect to other standards?
It builds on MS-ESS2-4, where students model condensation in the water cycle, and on probability in grade 7 math (7.SP.C.6, finding probabilities from data). It leads to MS-ESS2-6, which explains the global winds and ocean currents behind regional climates, and to MS-ESS3-2, which uses data to forecast hazards such as severe storms.
07
Related Standards
5 standards
These standards connect to MS-ESS2-5: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
3-ESS2-1Prerequisite
Represent weather data in tables and graphs to describe typical weather in a season
Lesson coming soon
MS-ESS2-4Prerequisite
Model the cycling of water through Earth's systems, driven by the sun and gravity
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