As a result of working with different materials and learning theories about the structure of matter:

Students understand the basic structure of atoms and the properties of elements.

• Describe the basic structure of atoms (including protons, neutrons and electrons) and how the atoms of one element are alike and different from other elements. (PIA1)

1. The chemical properties of an element are determined by its

a. atomic mass.
b. proton number.
c. electron arrangement.
d. atomic size.

2. The atomic number of iron is 26, and the atomic mass is 55.847. What do these numbers mean in regard to protons, electrons and neutrons?

a. There are 26 each of protons and neutrons, and the rest of the mass is the result of electrons.
b. There are 26 protons and 26 electrons. Some atoms of iron have 29 neutrons; the .847 shows that there is more than one isotope of iron.
c. There are 26 protons and 29 neutrons. Each particle has an atomic mass of 1.
d. There are 26 protons and 26 neutrons. Since neutrons have slightly more mass than protons, the mass is greater than 52.

3. Study the table below. Which atom has a net positive charge?

a. Atom W
b. Atom X
c. Atom Y
d. Atom Z

• Describe the organization of the elements in the periodic table, including the properties and electronic arrangements of elements in the first three periods. (PIA2)

4. What do all of the elements listed above have in common?

a. They are metals.
b. They are in the same period.
c. They have the same number of electrons.
d. They have four electrons in their outer shells.

Refer to this portion of the periodic table to answer the question that follows.

5. Which element in this group would be the least likely to react with other elements?

a. Boron
b. Carbon
c. Neon
d. Oxygen

6. Which of the following is the most important factor in determining an element’s place in the periodic table?

a. number of protons
b. number of neutrons
c. atomic charge
d. atomic density

The pictures below show the position of different elements on the periodic table.

7. Which picture has an X in the locations of the three elements that would be most similar in the way they react?

a.

X
X
X

b.

X	X	X

c.

X
	X
		X

d.

		X
	X
X

8. Oxygen has an atomic number of 8. Which of the following elements would you expect to be most similar to oxygen in terms of its chemical properties?

a. Nitrogen (N)
b. Fluorine (F)
c. Sulfur (S)
d. Chlorine (Cl)

Students understand the use of physical and chemical properties to classify and describe matter.

• Describe the different physical properties that are used to classify matter, including density, melting point and boiling point. (PIB1)

Archimedes, a Greek mathematician and physicist who lived more than 2200 years ago, is given credit for first discovering that:

An object immersed in a fluid will be pushed up by a buoyant force equal to the weight of the fluid displaced by the object.

The following are several ideas that relate to the statement above.

Floating Objects

• An object placed in a fluid will sink into the fluid until it has displaced a volume of fluid whose weight is equal to the weight of the object.

• An object will float in a fluid when the object has a density less than the density of the fluid.

Sinking Objects

• When an object sinks in a fluid, it displaces exactly its own volume of the fluid.

• An object will sink in a fluid when the object has a density greater than the density of the fluid.

Density

• The density of a substance is its mass divided by its volume.

• The density of water is one gram per cubic centimeter (1 g/cm 3 )

Use the above information to help you answer the following questions.

9. A wooden ball with a density of 0.8 grams per cubic centimeter (g/cm 3 ) and an aluminum ball with a density of 2.7 g/cm 3 are exactly the same size. Both are put in a glass of water. Which of the following statements is true?

a. Both balls will displace the same volume of water.
b. The aluminum ball will displace a greater volume of water than the wooden ball.
c. Both balls will displace the same weight of water.
d. The wooden ball will displace a greater volume of water than the aluminum ball.

10. Ice floats in water. From this statement it is reasonable to predict that, when a liter of water freezes to form ice, its _______.

a. density increases
b. weight increases
c. density decreases
d. weight decreases

11. Ice sinks in methyl alcohol that has a density of .8 grams per cubic centimeter (g/cm 3 ) but floats in liquid water. Based on this information, which of these conclusions is correct?

a. Ice is less dense than methyl alcohol.
b. Frozen water has the same density as liquid water.
c. The density of ice is between 0.8 g/cm 3 and 1 g/cm 3 .
d. Liquid water will also float on methyl alcohol.

- - -

12. Some lakes, such as the Great Salt Lake, accumulate soluble minerals, especially salt. In those lakes, people find it much easier to float than when they are in fresh water. Why is this?

a. The salt water has a greater density than fresh water.
b. People displace a smaller volume of fresh water than salt water.
c. Fresh water is denser causing people to sink.
d. This effect is only imaginary because floating depends on the skill of people.

• Explain that new substances are formed when atoms combine by transferring or sharing electrons (i.e., ionic and covalent bonding). (PIB2)

The reaction of element X ( ) with element Y ( O ) is represented in the following diagram:

13. Which equation properly describes the reaction between X and Y?

a. 3X +8Y —>X 3Y 8
b. 3X+6Y —>X 3Y 6
c. X +2Y —>XY2
d. 3X +8Y —>3XY 2 +2Y

• Explain the differences among atoms, elements, molecules, compounds and mixtures and give examples of each using common materials. (PIB3)

(no examples provided)