Fossils can be used to match up rock layers. As organisms change over time, they look different. Older fossils will look different than younger fossils. Some organisms only survived for a short time before going extinct. Knowing what organisms looked like at certain times also helps date rock layers. Some fossils are better than others for this use. The fossils that are very distinct at certain times of Earths history are called index fossils. Index fossils are commonly used to match rock layers. You can see how this works in Figure 2.30. If two rock layers have the same index fossils, then they're probably about the same age.
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QUESTION: What kind of fossils are used to date rock layers?

Greta ran to the corner with her older brother Tony. He had money for the ice cream truck in his pocket and she was very happy. The ice cream truck had been parked at the curb waiting for children for a very long time. The ice cream truck driver thought that no more children were coming to get ice cream so he started pulling away from the curb when they got to the corner. They yelled. They screamed, "Stop! Stop!" and jumped up and down on the side walk trying to get him to see them. The driver of the truck saw them, waved at them and smiled, pulled back to the curb and opened his truck up so that they could see everything that he had for sale. They were so excited. They saw some new treats. Tony wanted to try something new. He got an ice cream sundae with chocolate ice cream and nuts. He almost got a snow cone. Greta looked at everything that the ice cream truck had. She saw candy, ice cream cones, snow cones, and everything else. It all looked so good. But after looking at everything, she wanted to get an ice cream sandwich. She got the ice cream sandwich. She bit into it and smiled. It tasted so good. She felt so happy. Her brother, Tony, was happy too. He bit into his ice cream cone sundae and grinned. They walked home with their ice cream and told their mom about how close they came to not getting their ice cream at all. Their mom was happy that the truck had stopped for them. She said that they were very lucky to have gotten to the curb before the ice cream truck left.
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QUESTION: What did Greta's older brother have money for?

Alexis-Charles-Henri Clerel de Tocqueville (French: [aleksi SaRl aRi kleRel d@ tokvil]; 29 July 1805 - 16 April 1859) was a French political thinker and historian best known for his works Democracy in America (appearing in two volumes: 1835 and 1840) and The Old Regime and the Revolution (1856). In both of these, he analyzed the improved living standards and social conditions of individuals, as well as their relationship to the market and state in Western societies. Democracy in America was published after Tocqueville's travels in the United States, and is today considered an early work of sociology and political science. Tocqueville was active in French politics, first under the July Monarchy (1830-1848) and then during the Second Republic (1849-1851) which succeeded the February 1848 Revolution. He retired from political life after Louis Napoleon Bonaparte's 2 December 1851 coup, and thereafter began work on The Old Regime and the Revolution. He argued that the importance of the French Revolution was to continue the process of modernizing and centralizing the French state which had begun under King Louis XIV. The failure of the Revolution came from the inexperience of the deputies who were too wedded to abstract Enlightenment ideals. Tocqueville was a classical liberal who advocated parliamentary government, but was skeptical of the extremes of democracy.
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QUESTION: Which of Tocqueville's two best known works was published after the February 1848 Revolution?

Physical properties include the state of matter. We know these states as solid, liquid, or gas. Properties can also include color and odor. For example, oxygen is a gas. It is a major part of the air we breathe. It is colorless and odorless. Chlorine is also a gas. In contrast to oxygen, chlorine is greenish in color. It has a strong, sharp odor. Have you ever smelled cleaning products used around your home? If so, you have probably smelled chlorine. Another place you might smell chlorine is at a public swimming pool. The chlorine is used to kill bacteria that may grow in the water. Other physical properties include hardness, freezing, and boiling points. Some substances have the ability to dissolve in other substances. Some substances cannot be dissolved. For example, salt easily dissolves in water. Oil does not dissolve in water.
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QUESTION:
Where are two places one could use chlorine?