chemistry review 1

Use the periodic table to identify the group numbers and period numbers of the following elements: a. carbon, C b. argon, Ar c. chromium, Cr d. barium, Ba

-14,2 -18,3 -6,4 -2,6

Write a brief paragraph that shows that you understand the following terms and the relationships between them: atom, molecule, compound, and element.

Elements are naturally occurring substances with a certain number of atoms arranged in a specific way to give it a unique chemical structure . When two or more elements combine or chemically changed under specific temperatures & pressures, they form Compounds. Elements themselves are made up of atoms, which are building blocks of all matter. When atoms of different kind combine, they form complex molecules. For example, Hydrogen is an element comprising of 2 Hydrogen atoms in its natural state. Oxygen is an element comprising of 2 Oxygen atoms in its natural state. When these two elements are combined under 298 deg celsius, water is formed.

What is the difference between extensive properties and intensive properties?

Extensive properties, such as mass and volume, depend on the amount of matter being measured. Intensive properties, such as density and color, do not depend on the amount of the substance present.

An unknown element is shiny and is found to be a good conductor of electricity. What other properties would you predict for it?

May be malleable and ductile and a good conductor of energy as heat

property

an attribute, quality, or characteristic of something.

What is a plasma?

an ionized gas consisting of positive ions and free electrons in proportions resulting in more or less no overall electric charge, typically at low pressures (as in the upper atmosphere and in fluorescent lamps) or at very high temperatures (as in stars and nuclear fusion reactors).

Suppose different parts of a sample material have different compositions. What can you conclude about the material?

it is a heterogenous mixture

Identify each of the following as either a physical change or a chemical change. Explain your answers. a. A piece of wood is sawed in half. b. Milk turns sour. c. Melted butter solidifies in the refrigerator.

-physical, because the wood remains wood -chemical, because the milk changes composition, as signified by the change in flavor -physical, because the butter remains butter

Use the periodic table to write the names of the elements that have the following symbols, and identify each as a metal, nonmetal, metalloid, or noble gas. a.K c.Si e.Hg b.Ag d.Na f. He

-potassium, metal -silver,metal -silicon,metalloid -sodium,metal -mercury,metal -helium,nobel gas

What is meant by a change in state?

A change of state is a change in the object from a solid to liquid or from a solid to gas or from liquid to solid. ice changing into water is an example of a change in state

chemical property

Chemistry. a property or characteristic of a substance that is observed during a reaction in which the chemical composition or identity of the substance is changed: Combustibility is an important chemical property to consider when choosing building materials.

Compare the physical properties of metals, non- metals, metalloids, and noble gases, and describe where in the periodic table each of these kinds of elements is located.

Metals have a shiny luster, are malleable as well as ductile, have a high melting point, and are excellent conductors of heat and electricity. Nonmetals are generally not as shiny, are brittle, have low density, low melting point, and are poor conductors of electricity and heat. Metalloids are solids, can be both shiny and dull, are ductile, malleable, and conduct heat and electricity better than nonmetals but not as well as metals. The noble gases are all odorless and colorless. They have no physical shape. Metals are on the left side, nonmetals are on the right side, metalloids are in a stair like shape on the right side, and noble gases take up the far right column.

Distinguish between a physical change and a chemical change.

There are several differences between a physical and chemical change in matter or substances. A physical change in a substance doesn't change what the substance is. In a chemical change where there is a chemical reaction, a new substance is formed and energy is either given off or absorbed.

What is the significance of the vertical columns of the periodic table? What is the significance of the horizontal rows?

Vertical columns are elements with similar properties. This is because they have the same number of electrons in their outer shell. It is the number of electrons in the outer shell that mostly determines how an element reacts with other elements. The horizontal rows are not so significant. Essentially the weight or size of the element (technically it is the number of Protons and therefore electrons) increases as you move to the right and down.

what is chemistry

the branch of science that deals with the identification of the substances of which matter is composed; the investigation of their properties and the ways in which they interact, combine, and change; and the use of these processes to form new substances.

How are properties useful in classifying materials?

QUICK ANSWER An object's properties are characteristics that delineate it from other objects. Properties can be anything from composition to color to ductility. Without knowing an object's properties, it is impossible to characterize it. For example, looking at some common properties of metals helps to differentiate them from non-metals or metalloids.

What is meant by the word chemical, as used by scientists?

Referring to the use or presence of chemicals in a scientific theory or experimentation.

Pick an object you can see right now. List three of the object's physical properties that you can observe. Can you also observe a chemical property of the object? Explain your answer.

So, let's say that we pick an object like a sheet of paper. Paper would be solid, whatever color it is is also a physical property, it has a certain mass, it has a certain density. All of these are physical properties. A chemical property would be the paper's flammability. You wouldn't be able to observe this unless the paper was reacting with oxygen (burning). For salt and sugar. Physical properties. They are both white, they are both soluble in water, they are both solids and are crystalline. However, they have different melting points and different densities. Chemical properties, sugar can burn, salt cannot. They also have a different chemical composition.

Suppose element X is a poor conductor of elec- tricity and breaks when hit with a hammer. Element Z is a good conductor of electricity and heat. In what area of the periodic table does each element most likely belong?

X is probably a nonmetal on the right side of the tabel. Z is a metal on the left side or in the middle of the tabel

How does the composition of a pure compound differ from that of a mixture?

composition of a pure compound is consistent and has unique properties of itself. composition of a mixture ALWAYS retains the properties of what makes it up.

How does a solid differ from a liquid?

gas vibrate and move freely at high speeds. liquid vibrate, move about, and slide past each other. solid vibrate (jiggle) but generally do not move from place to place.