2 (h.c.a.) CO2 and the Greenhouse Effect
Carbon Dioxide makes up less than 1 percent of the Earth’s atmosphere. Carbon dioxide is not an element like oxygen and nitrogen. It is a compound because it is made of a carbon atom and two oxygen atoms. The carbon and oxygen are chemically bonded in a 2-1 ratio. Compounds cannot be separated by physical means. However compounds can by broken down through a chemical change. Photosynthesis is a chemical change where plants break down carbon dioxide. Sugar and oxygen are new substance in this reaction.
Carbon Dioxide Each molecule of carbon dioxide has one atom of carbon and two atoms of oxygen. Carbon dioxide is essential to life. Plants must have carbon dioxide to produce food. When the cells of plants and animals break down food to produce energy, they give off carbon dioxide as a waste product.
When fuels such as coal and gasoline are burned, they release carbon dioxide. Burning these fuels increases the amount of carbon dioxide in the atmosphere.
All matter is made of elements, but most elements in nature are found combined with other elements. A compound is a pure substance made of two or more elements chemically combined in a set ratio. A compound may be represented by a chemical formula, which shows the elements in the compound and the ratio of atoms. For example, part of the gas you exhale is carbon dioxide. Its chemical formula is CO2. The number 2 below the symbol for oxygen tells you that the ratio of carbon to oxygen is 1 to 2. (If there is no number after the element’s symbol, the number 1 is understood.)
When elements are chemically combined, they form compounds having properties that are different from those of the uncombined elements. Table sugar (C12H22O11) is a compound made of the elements carbon, hydrogen, and oxygen. The sugar crystals do not resemble the gases oxygen and hydrogen or the black carbon you see in charcoal.
Recall that gases in Earth’s atmosphere hold in heat from the sun, keeping the atmosphere at a comfortable temperature for living things. The process by which gases in Earth’s atmosphere trap this energy is called the greenhouse effect. Notice that sunlight does not heat the air in the greenhouse directly. Instead, sunlight first heats the soil, benches, and pots. Then infrared radiation from these surfaces heats the air in the greenhouse. The greenhouse effect in Earth’s atmosphere is similar in some ways.
Gases in the atmosphere that trap energy are called greenhouse gases. Carbon dioxide, water vapor, and methane are some of the greenhouse gases. Many scientists have hypothesized that human activities that add greenhouse gases to the atmosphere may be warming Earth’s atmosphere.
Changing Levels of Carbon Dioxide
Scientists think that an increase in carbon dioxide is a major factor in global warming. For example, the burning of wood, coal, oil, and natural gas adds carbon dioxide to the air. During the last 100 years, these activities have increased greatly in many different countries. The carbon dioxide in Venus’s atmosphere traps heat so well that Venus has the hottest surface of any planet. At 460°C, its average surface temperature is hot enough to melt lead. This trapping of heat by the atmosphere is called the greenhouse effect.
Carbon Dioxide Each molecule of carbon dioxide has one atom of carbon and two atoms of oxygen. Carbon dioxide is essential to life. Plants must have carbon dioxide to produce food. When the cells of plants and animals break down food to produce energy, they give off carbon dioxide as a waste product.
When fuels such as coal and gasoline are burned, they release carbon dioxide. Burning these fuels increases the amount of carbon dioxide in the atmosphere.
All matter is made of elements, but most elements in nature are found combined with other elements. A compound is a pure substance made of two or more elements chemically combined in a set ratio. A compound may be represented by a chemical formula, which shows the elements in the compound and the ratio of atoms. For example, part of the gas you exhale is carbon dioxide. Its chemical formula is CO2. The number 2 below the symbol for oxygen tells you that the ratio of carbon to oxygen is 1 to 2. (If there is no number after the element’s symbol, the number 1 is understood.)
When elements are chemically combined, they form compounds having properties that are different from those of the uncombined elements. Table sugar (C12H22O11) is a compound made of the elements carbon, hydrogen, and oxygen. The sugar crystals do not resemble the gases oxygen and hydrogen or the black carbon you see in charcoal.
Recall that gases in Earth’s atmosphere hold in heat from the sun, keeping the atmosphere at a comfortable temperature for living things. The process by which gases in Earth’s atmosphere trap this energy is called the greenhouse effect. Notice that sunlight does not heat the air in the greenhouse directly. Instead, sunlight first heats the soil, benches, and pots. Then infrared radiation from these surfaces heats the air in the greenhouse. The greenhouse effect in Earth’s atmosphere is similar in some ways.
Gases in the atmosphere that trap energy are called greenhouse gases. Carbon dioxide, water vapor, and methane are some of the greenhouse gases. Many scientists have hypothesized that human activities that add greenhouse gases to the atmosphere may be warming Earth’s atmosphere.
Changing Levels of Carbon Dioxide
Scientists think that an increase in carbon dioxide is a major factor in global warming. For example, the burning of wood, coal, oil, and natural gas adds carbon dioxide to the air. During the last 100 years, these activities have increased greatly in many different countries. The carbon dioxide in Venus’s atmosphere traps heat so well that Venus has the hottest surface of any planet. At 460°C, its average surface temperature is hot enough to melt lead. This trapping of heat by the atmosphere is called the greenhouse effect.
