Carbon cycle What is a Cycle? What is the Carbon Cycle? What gas do humans and animals exhale? Nitrogen cycle Phosphorus cycle Hydrologic cycle What is a Cycle? You may have studied the water cycle or the rock cycle in school. These are just two examples of cycles. Very simply, when scientists talk about cycles, they are talking about sequences of events that repeat themselves. Some cycles are very simple. For example, the seasons of the year represent a cycle in that they always repeat – Winter, Spring, Summer, Fall, and then back to Winter! The nitrogen and carbon cycles are very complex cycles. They fit into the category called biogeochemical cycles. Earth's Water Cycle Water is always on the move. Rain falling where you live may have been water in the ocean just days before. And the water you see in a river or stream may have been snow on a high mountaintop. Water can be in the atmosphere, on the land, in the ocean, and even underground. It is recycled over and over through the water cycle. In the cycle, water changes state between liquid, solid (ice), and gas (water vapor). Most water vapor gets into the atmosphere by a process called evaporation. This process turns the water that is at the top of the ocean, rivers, and lakes into water vapor in the atmosphere using energy from the Sun. Water vapor can also form from snow and ice through the process of sublimation and can evaporate from plants by a process called transpiration. The water vapor rises in the atmosphere and cools, forming tiny water droplets by a process called condensation. Those water droplets make up clouds. If those tiny water droplets combine with each other they grow larger and eventually become too heavy to stay in the air. Then they fall to the ground as rain, snow, and other types of precipitation. Most of the precipitation that falls becomes a part of the ocean or part of rivers, lakes, and streams that eventually lead to the ocean. Some of the snow and ice that falls as precipitation stays at the Earth surface in glaciers and other types of ice. Some of the precipitation seeps into the ground and becomes a part of the groundwater. Water stays in certain places longer than others. A drop of water may spend over 3,000 years in the ocean before moving on to another part of the water cycle while a drop of water spends an average of just eight days in the atmosphere before falling back to Earth. The Carbon Cycle What is the Carbon Cycle? What gas do humans and animals exhale? Carbon is an element. It is part of oceans, air, rocks, soil and all living things. Carbon doesn’t stay in one place. It is always on the move! * Carbon moves from the atmosphere to plants. In the atmosphere, carbon is attached to oxygen in a gas called carbon dioxide (CO2). With the help of the Sun, through the process of photosynthesis, carbon dioxide is pulled from the air to make plant food from carbon. * Carbon moves from plants to animals. Through food chains, the carbon that is in plants moves to the animals that eat them. Animals that eat other animals get the carbon from their food too. * Carbon moves from plants and animals to the ground. When plants and animals die, their bodies, wood and leaves decay bringing the carbon into the ground. Some becomes buried miles underground and will become fossil fuels in millions and millions of years. * Carbon moves from living things to the atmosphere. Each time you exhale, you are releasing carbon dioxide gas (CO2) into the atmosphere. Animals and plants get rid of carbon dioxide gas through a process called respiration. * Carbon moves from fossil fuels to the atmosphere when fuels are burned. When humans burn fossil fuels to power factories, power plants, cars and trucks, most of the carbon quickly enters the atmosphere as carbon dioxide gas. Each year, five and a half billion tons of carbon is released by burning fossil fuels. That’s the weight of 100 million adult African elephants! Of the huge amount of carbon that is released from fuels, 3.3 billion tons enters the atmosphere and most of the rest becomes dissolved in seawater. * Carbon moves from the atmosphere to the oceans. The oceans, and other bodies of water, soak up some carbon from the atmosphere. Carbon dioxide is a greenhouse gas and traps heat in the atmosphere. Without it and other greenhouse gases, Earth would be a frozen world. But humans have burned so much fuel that there is about 30% more carbon dioxide in the air today than there was about 150 years ago. The atmosphere has not held this much carbon for at least 420,000 years according to data from ice cores. More greenhouse gases such as carbon dioxide in our atmosphere are causing our planet to become warmer. Carbon moves through our planet over longer time scales as well. For example, over millions of years weathering of rocks on land can add carbon to surface water which eventually runs off to the ocean. Over long time scales, carbon is removed from seawater when the shells and bones of marine animals and plankton collect on the sea floor. These shells and bones are made of limestone, which contains carbon. When they are deposited on the sea floor, carbon is stored from the rest of the carbon cycle for some amount of time. The amount of limestone deposited in the ocean depends somewhat on the amount of warm, tropical, shallow oceans on the planet because this is where prolific limestone-producing organisms such as corals live. The carbon can be released back to the atmosphere if the limestone melts or is metamorphosed in a subduction zone. The Water Cycle 1 How does Water Vapour get into the Air? Give two sources. Answer 2 What is Precipitation in the Water Cycle? Answer 3 Why is the Sea Salty? Answer 4 Give one process which remove Salt from the Sea. Answer The Carbon Cycle 5 Give two process which release Carbon Dioxide into the Atmosphere. Answer 6 Give one process which removes Carbon Dioxide from the Atmosphere. Answer 7 Does Carbon Dioxide dissolve in Rain Water? Answer 8 How can Limestone release Carbon Dioxide into the Atmosphere? Answer The Nitrogen Cycle 9 What is Fixing? Answer 10 Why do Plants need Nitrogen? Answer 11 What type of bacteria turn Nitrite into Nitrate in the Soil? Answer 12 What type of bacteria turn Nitrate in the Soil into Nitrogen in the Atmosphere? Answer The Early Atmosphere 13 Name two Gases which were present in the Earth's early Atmosphere? Answer 14 Where did the Gases in the Earth's early Atmosphere come from? Answer 15 Where did the Oceans come from? Answer 16 What were the First Life Forms? Answer 17 Which Gas do Green Plants add to the Atmosphere? Answer 18 Where did Nitrogen in the Earth's Atmosphere come from? Answer The Atmosphere Today 19 How is Ozone Produced high up in the Atmosphere? Answer 20 How does the Ozone Layer Protect our planet? Answer 21 Name one Chemical which can produce a hole in the Ozone Layer? Answer 22 Give one risk of having a hole in the Ozone Layer. Answer 23 What is the Proportion of Nitrogen in the Atmosphere Today? Answer 24 What is the Proportion of Oxygen in the Atmosphere Today? Answer 25 What is the Proportion of Argon in the Atmosphere Today? Answer 26 Which Experiment can show the Proportion of Oxygen in the Air Today? Answer 27 Give one Use of Nitrogen. Answer 28 Give one Use of Oxygen. Answer 29 Give one Use of Argon. Answer http://www.gcsescience.com/science-chemistry-revision.htm