Unit C, Lesson 1

HOW DOES SUNLIGHT AFFECT AIR TEMPERATURE?

It’s summer. You wake up and bright sunlight streams in your window. It

makes you squint. As the sun rises in the sky, the day gets warmer and warmer.

Yes! It’s a beautiful summer day!

What is the warmest part of the day?a. Morningb. Afternoonc. Evening

CHANGES IN AIR TEMPERATURE

WHY AFTERNOON?

The temperature of the air has to do with how much sunlight (light energy from the sun) reaches the earth.

Sunlight passes through air…but does NOT heat it!

Light energy from the sun hits liquids and solids on the surface of the earth.

When liquids and solids get warm, they warm the air above them.

Earth’s surface does NOT heat evenly.

Why? Well, check it out…

WHICH SEASON HAS LONGER DAYS?SUMMER OR WINTER

The number of hours of daylight also affects air temperature.

More Daylight = More Warmth

DIFFERENT SURFACES

Imagine: It’s one of those really hot days. You decide to go swimming. In your bare feet, you walk across the pavement toward the lake. YIKES! The pavement is hot! You run to the beach. Yow! The sand is almost as hot! Quickly, you head for some grass. Ahh, that’s better! The grass is much cooler than the sand or the pavement.

WHY WAS THE GRASS COOLER?

Different surfaces absorb different amounts of light energy. What does that mean?

Some surfaces get hot faster than others.

Fast Absorbers Slow Absorbers

Blacktop Grass

Cement water

buildings

LET’S GO BACK TO THE BEACH…

The ocean heats up

more slowly.

The air above the ocean will stay cooler than the air above the

land.

The land further away

from the ocean heats

up more quickly.

The air above the land away

from the ocean stays

warmer.

MEASURING AIR TEMPERATURE

Thermometer When the air around the liquid gets warmer,

the liquid gets warmer. When the liquid gets warmer, it spreads out

and moves up the thermometer. When it cools, the opposite happens.

°C AND °F

C = Celsius (a metric scale for measuring temperature)

F = Fahrenheit (a customary scale for measuring temperature)

Higher Number = Warmer temperature Lower Number = Cooler temperature

LET’S REVIEW

Why are air temperature usually higher in the late afternoon than in the morning? The direct rays of the sun hit the surface of the

earth near noon, but it takes time for the surface of the earth to heat the air. Therefore, air temperatures are often higher in the late afternoon than in the morning.

Why is the air above the warm surfaces warmer than the air above cooler surfaces? Warmer surfaces heat the air above them more

than cooler surfaces do.

What causes the liquid in a thermometer to rise in he tube? When warm air around the thermometer heats

the liquid, it expands and moves up the tube.

RANGE, MEDIAN, AND MODE

What is the range, median, and mode of this data:

90, 80, 76, 66, 98, 85, 76

Range = 32Median = 80Mode = 76