Unit 3 Summative Review #1

What matter are we talking about when we refer to temperature and wind? (from L1)

• There is no matter needed.

• Air molecules

• Dust molecules

• Heat molecules

Answer explanation

Remember, matter is needed for weather to occur. Air molecules are the ones moving and interacting.

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What are the atmospheric conditions that make weather? (from L1)

• Temperature, precipitation, wind, humidity, clouds, and air pressure

• River speed and velocity along with precipitation and humidity

• The salinity of the Ocean and temperature

• Temperature and cloud cover only

Answer explanation

You need all 6 items together to make every type of weather we encounter.

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Which of the following statements are true about temperature? Select all that apply. (from L1)

• Temperature is determined by cloud cover and wind speed.

• Temperature is a measure of the thermal energy of matter.

• Thermal energy is the kinetic energy of the particles in an object, a unit of liquid, or a parcel of air.

• The warmer the temperature the slower the particles move.

Answer explanation

There are two correct answers here. Temperature and thermal energy go together! Thermal energy is the kinetic energy of the particles. So how fast or slow they are moving! The hotter something is, the faster the molecules move! Therefore, gas molecules move much faster than the molecules in a solid.

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We know that when light hits any matter it can be reflected, absorbed, or reflected. How does the absorption of light affect the temperature of an object? (from L2)

• When light is absorbed, light energy is transformed into thermal energy but it does not affect the temperature of the object.

• When light is absorbed, the temperature of the object increases.

• We cannot measure the temperature of light energy.

• When light is absorbed, the temperature holds steady even when the light source is removed.

Answer explanation

Light is energy and adding it speeds up the molecules and therefore the temperature increases.

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Lei and Ching are having an argument about why the air feels so warm when the sun is shining. Lei says that energy from the sun heats the air around the Earth.  Ching says that the sun heats the Earth first and that heats the air. Select which person is correct and why? (from L2)

• They are both right. Earth’s atmosphere (or the air around us) is heated in two ways. Some of Earth’s atmosphere is heated directly by the sun as it transfers thermal energy to the air particles/molecules. The particles move faster and the temperature gets warmer. But, most of the sun’s energy passes through the atmosphere to the surface of the Earth. The surface/ground absorbs thermal energy and then transfers it to the air particles/molecules.

• Neither is correct. The water vapor in the atmosphere releases thermal energy as it condenses to form clouds. The thermal energy heats the air molecules.

• Ching is correct most of the solar radiation gets absorbed by the Earth and converted to thermal energy.

• Lei is correct. As the sun’s rays move through the atmosphere, most of the air molecules are directly heated by light energy.

Answer explanation

Both are correct! Think about the model drawn in the classroom. This is part of what helps make the convection in our atmosphere.

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Which of the following statements are true about conduction? Select all that apply. (from L2)

• In conduction, particles collide and transfer energy from one particle to another.

• For conduction to occur, two objects (matter) must be in contact with each other.

• Conduction does not occur within one object. The energy transfer is between two or more objects or types of matter.

• Most of the air molecules in our atmosphere are heated by conduction.

Answer explanation

This goes back to air molecules and how fast they move. The higher the temperature, the faster the molecules are moving so when they collide, the more energy they transfer. This also helps contribute to the convection too!

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In electric ovens, the heat in the oven comes from the bottom when you bake something. However, cookies baking on the top shelf get done before cookies on the bottom shelf, even though the bottom shelf is closer to the heat source. Why does this happen? (from L3)

• The heat rises from the cookies on the bottom shelf, so some of the heat from the cookies helps to cook the cookies on the top shelf.

• The oven heats the air at the bottom. The air becomes less dense than the air at the top of the oven and rises. The hotter air stays at the top of the oven and so it transfers more energy to the cookies, and the cookies on the top shelf cook faster.

• The oven walls absorb a lot of the heat and the top shelf is closest to the top wall.

• There is more air above the lower pan so it loses more heat to the air so the pan on the upper shelf appears to heat faster.

Answer explanation

This is convection that we experience in our every day lives!!

Convection ovens work the same way as a regular oven, but use a fan to help circulate the air more evenly for more even cooking.

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If you hold your finger next to the flame on a candle like the one in the picture, you can feel the heat, but you will not get burned; however, if you hold your finger above the candle, you will get burned.  Why? (from L3)

• The candle absorbs the heat from the lower part of the flame so the top part of the flame is hotter.

• The sides of the candle are cooler than the flame so it doesn’t get as hot on the sides.

• The shape of the candle flame directs the heat out through the top so if you place your hand at the top of the flame you could get burned.

• As the heated air rises, cooler air moves in to take its place. This causes convection and more hot air to rise. Some thermal energy is radiated from the flame to the side of the candle, and that is why you feel the heat. It is hotter above the candle because of convection.

Answer explanation

This is another everyday convection we experience. This is also similar to how a room is heated by our furnace (or similarly cooled by our AC).

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What differences in air masses can cause wind? Use the model to help you explain why this happens. (from L3)

• When two warm air masses come together the more warm mass moves over the less warm and causes wind.

• Where there is a temperature or density difference in two air masses, the warmer air rushes to the colder air to help it increase its temperature. When the warm air moves to the cold air, that is what causes wind.

• The temperature/density differences between cooler and warmer air cause wind. Hotter, less dense air rises. When that happens the cooler, denser air sinks and moves in to take the place of the rising air. The movement is wind.

• Wind happens when the higher air mass sinks toward the ground and pushes the lower air mass away.

Answer explanation

This is convection! The larger the difference between temperature/density of the two fronts, the more windy it is! This is also why it is windy during a storm and the wind picks up right before the storm hits.

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What is the relationship between air pressure and temperature? (from L4)

(This was one of the most missed questions on the L4 Assessment- HINT: think of the 3 things that go together!!)

• The greater the air pressure the hotter the temperature

• The greater the air pressure the less dense it is.

• The greater the air pressure, the more dense the air mass and thus it is colder.

• The greater the air pressure the greater the density.

Answer explanation

Did you remember that the three things that go together are: high density, cold temps, and high air pressure (and similarly low density, warm temps, and low air pressure also go together!)