CHAPTER 5: WEATHER FACTORS Essential Question: What Factors Affect the Weather?

LESSON 1: HEAT TRANSFER Objectives To Keep in Mind

VOCABULARY Atmosphere Hydrosphere Weather Thermal Energy Temperature Thermometer Heat Convection Conduction Radiation Convection Currents

FROM THE FREEZER TO THE TABLE French fries are on many restaurant menus. But have you ever wondered how they get from the freezer to the table? It takes a little science in the kitchen to make it happen. First, you heat oil in a fryer until it’s around 340ºF. Then, the frozen potato slices are dropped in. Hot oil moves from the bottom of the fryer and begins to heat the potatoes. Exposure to so much heat causes the water in the potatoes to boil. This is indicated by bubbles rising to the surface of the oil. As the outside of the potato heats up, it transfers heat to the inside of the potato slice. In a matter of minutes it’s crunchy on the outside and soft on the inside.

FROM THE FREEZER TO THE TABLE Explain in your words what happens when the potatoes are exposed to heat. The outside get warm first and heat move inside

HOW IS EARTH A SYSTEM? Earth is a system made up of different parts. The atmosphere is the envelope of gases that surround the planet. The hydrosphere is made up of all the water on Earth. The atmosphere and hydrosphere constantly interact. For example, when energy from the sun warms the gases in the atmosphere and the water in the hydrosphere, the water evaporates and forms vapor in the atmosphere. The vapor may form clouds and then fall back to the surface of Earth as rain. The condition of Earth’s atmosphere at a particular time and place is weather. As the interactions between Earth’s parts change, so does the weather.

HOW IS TEMPERATURE MEASURED? All substances are made up of tiny particles (atoms and molecules) that are constantly moving. The faster the particles move, the more energy they have. Thermal energy measures the total energy of motion in the particles of a substance. Temperature is the average amount of energy of motion of each particle of a substance. Air temperature is usually measured with a thermometer. A thermometer is a device that measures temperature. Temperature is measured in units called degrees. Two temperature scales are the Celsius scale and the Fahrenheit scale.

Heat Transfer Converting Units Temperature readings can be converted from the Fahrenheit scale to the Celsius scale using the following equation:

HOW IS HEAT TRANSFERRED? Heat is thermal energy that is transferred from a hotter object to a cooler one. Heat is transferred in three ways: convection, conduction, and radiation. Atoms and molecules in fluids (liquids and gases) can move easily. As they move, their energy moves with them. The transfer of heat by the movement of a fluid is called convection.

HOW IS HEAT TRANSFERRED? The transfer of heat between two substances that are in direct contact is called conduction. When a fast moving molecule bumps into a slower moving molecule, the faster one transfers some of its energy to the slower one. The closer together the molecules are in a substance, the better they conduct heat. Conduction works best in some solids, such as metals, but not as well in liquids and gases. Radiation is the direct transfer of energy by electromagnetic waves. Most of the heat that you feel from the sun travels to you as infrared radiation, which you cannot see but can feel.

Heat Transfer Heat transfer occurs when a warm radiator heats a room. What type of heat transfer could keep the paper in the air? Heat Transfer

HOW IS HEAT TRANSFERRED? Radiation, conduction, and convection work together to heat the troposphere. During a sunny day the land gets warmer than the air. But because air doesn’t conduct heat well, only the first few meters of the troposphere are heated by conduction. When air at ground level warms, its molecules spread out, making it less dense. Cooler denser air sinks toward the surface, forcing the warmer air to rise. The upward movement of warm air and the downward movement of cool air form convection currents. Heat is transferred mostly by convection within the troposphere.

EXPLAIN Radiation, conduction, and convection work together to heat the troposphere.