Chemistry 2.5.4 TST Question 1: Matter and Energy

a. From the above description of a candle flame, list at least three things that are matter and three things that are not matter. (6 points)
Matter
1. Oxygen
2. Carbon dioxide
3. Water vapor
Not Matter
1. Heat
2. Light
3. The time it takes for the candle to melt

b. Give one example of a phase change from the above discussion, and state what matter is experiencing the phase change.
The candle experiences a phase change when it is being melted by heat, it turns from a solid to a liquid.

c. Give one example of an energy conversion from the above discussion, and state what kind of energy conversion it is.
The candle burning is an example of energy conversion, it changed from chemical potential energy to heat energy.

Question 2: The Laws of Conservation of Matter and Energy
a. Answer the following questions about the law of conservation of matter.
i. Briefly state what the law says.
Matter can be conserved, but not destroyed.

ii. How could you state the law of conservation of matter differently, in terms of what happens during a chemical reaction?
Matter can change forms, but never loses or gains any matter.

iii. What changes can matter undergo?
Matter can undergo phase changes, such as turning from solid to liquid via melting.

b. Answer the following questions about the law of conservation of energy. (3 points)
i. Briefly state what the law says.
Energy is conserved, but never lost.

ii. What changes can energy undergo?
Energy can be converted into different kinds of energy, but energy is never lost.

c. Considering only the total energy and total matter (not changes in energy or matter), in what kind of system(s) does each law of conservation apply?
They never lose or gain anything.

d. According to Einstein's equation, what is another way matter and energy can change?
Matter can be turned into energy, and energy to matter.

Question 3: The Elements
a. What do all atoms of one element have in common?
Atoms of one element usually have the same atomic number.

b. What can be said about the number of electrons and neutrons an atom of one element can have?
The number of electrons and neutrons an atom of one element has determines its electrical charge.

c. Explain how the existence of isotopes and ions relates to differences in the number of neutrons and electrons within atoms of an element?
Isotopes and ions relate to differences in the numbers of ions because they can change the atomic mass or charge.

Question 4: Valence Electrons and the Octet Rule
a. Name one group on the periodic table that has very low reactivity. How many valence electrons are in the stable group?
Group 18. There are 8 valence electrons in this group.

b. Fluorine (F), a halogen, is very reactive. It often forms an ion with a 1– charge. How does this make it more stable?
This makes it more stable because it has less reactive charge.

Question 5: The Photoelectric Effect
a. Briefly describe what happens in the photoelectric effect.
In the photoelectric effect, electrons are forced out from the surface of a metal when light shines on it.

b. How did Albert Einstein explain the photoelectric effect?
He explained that light comes in set amounts of energy, and if it has enough energy, the set of energy can remove an electron from an atom.

c. Albert Einstein received the Nobel Prize for explaining the photoelectric effect. How did his explanation change science?
His explanation changed science because it led to quantum mechanics.

d. How did Einstein's explanation of the photoelectric effect eventually affect Bohr's model of the atom?
Einstein's explanation affected Bohr’s model by showing there was an electron cloud around an atom.

Question 6: The Periodic Table
a. What is "periodic" on the periodic table?
The patterns that are shown by atoms.

b. An atom has a mass number of 7 and an atomic number of 3.
i. What is the element's symbol?
Li.

ii. How many protons does it have?
It has 3.

iii. How many neutrons does it have?
It has 4.

iv. How many electrons does it have?
It has 0.

v. If it has a charge of 1+, how many electrons does it have?
It has 2 electrons.

vi. It has an isotope with atomic mass 6. How would it be identified in isotope notation?
6/3Li^0

vii. How many neutrons does this isotope have?
3.

viii. What is the name of the group, or family, is it in?
Alkali metals.

Question 7: Family Properties
a. Compare the halogen family with the noble gas family in terms of reactivity.
The halogen family is very reactive, and the noble gas family is very unreactive.

b. Compare the alkali metals family with the halogen family in terms of metal and nonmetal members.
The alkali metals family has more metals than the halogen family.

c. Compare the alkali metals with the alkaline earth metals in terms of reactivity.
Alkaline earth metals are generally more reactive than alkali metals.