1st Semester Review Chapters 1-4

Question 1

What are chemical and physical properties? Provide examples of each.

Answer 1

A chemical property describes a substance’s ability to participate in chemical reactions.
Ex) reaction with oxygen/rusting, flammability, rotting
A physical property is something that can be determined without changing the identity of a substance
Ex) texture, state, melting point, boiling point

Question 2

What is a chemical change?

Answer 2

Chemical changes occur when the identities of the substance change and a new substance or substances are formed
Ex) baking a cake

Question 3

What is a physical change?

Answer 3

A physical change are changes in which the identity of a substance does NOT change.
Ex) ice melting

Question 4

Define volume.

Answer 4

the space an object occupies

Question 5

Define mass.

Answer 5

the quantity of matter in an object

Question 6

What is density?

Answer 6

mass / volume
(the degree of compactness of a substance)

Question 7

Define atom.

Answer 7

the smallest unit of an element that maintains the properties of that element

Question 8

Define pure substance.

Answer 8

Pure substances are substances that are made up of only one kind of particle and have a fixed or constant structure
ex) elements and compounds

Question 9

Define molecule.

Answer 9

the smallest unit of a substance that keeps all the physical and chemical characteristics of that substance

Question 10

Define theory.

Answer 10

A plausible explanation of a body of observed natural phenomena

Question 11

Define law.

Answer 11

A behavior in the natural world that is always true

Question 12

Define endothermic reaction.

Answer 12

the process in which heat is being absorbed from the environment
ex) a cake is placed into an oven and baked

Question 13

Define exothermic reaction.

Answer 13

A systems release of heat into the environment
ex) coal burns in a furnace, producing light and heat

Question 14

Define kinetic energy.

Answer 14

the energy of an object that is due to the object’s motion

Question 15

Define specific heat.

Answer 15

the amount of heat required to raise the temperature of one gram of that substance by one degree Celsius

Question 16

Explain the law of conservation of mass.

Answer 16

Mass is neither created nor destroyed in a chemical reaction, it is conserved.
Formula: mass reactants= mass products

Question 17

Explain the law of conservation of energy.

Answer 17

In any chemical reaction or physical process, energy may change from one form to another, but it is neither created nor destroyed.

Question 18

Define isotope.

Answer 18

Different atoms of the same element that have the same number of protons but different number of neutrons

Question 19

What is a period?

Answer 19

A horizontal row of elements in the periodic table that has increasing atomic numbers

Question 20

What is a group?

Answer 20

a vertical column of elements in the periodic table that share chemical properties

Question 21

Define alloy.

Answer 21

A homogenous mixture of two or more metals

Question 22

Define electron shielding.

Answer 22

Inner electrons shield outer electrons from the nucleus

Question 23

State the periodic law.

Answer 23

The repeating physical and chemical properties of elements change periodically with their atomic number.

Question 24

Give evidence of chemical changes.

Answer 24

Change in color, formation of bubbles, gas being formed, odor change, temperature change

Question 25

Define homogeneous mixture.

Answer 25

mixture that has a uniform composition throughout and always has a single phase; a solution

Question 26

Define heterogeneous mixture.

Answer 26

mixture that does not have a uniform composition and in which the individual substances remain distinct

Question 27

Define ground state.

Answer 27

the lowest allowable energy state of an atom

Question 28

In division and multiplication, the answer must not have more significant figures than the ____

Answer 28

Number in the calculation with the fewest significant figures.

Question 29

Describe precision.

Answer 29

sameness of measurements, agreement among numerical values, reproducibility of measurements

Question 30

The SI unit for energy is called

Answer 30

joules

Question 31

What are Mendeleev’s contributions to the periodic table?

Answer 31

modern periodic table, left gaps for elements that were yet to be discovered, arranged the elements according to their atomic weight

Question 32

What are the names of the electron orbital shapes? How many electrons can be found in each?

Answer 32

s orbital: two electrons, p orbital: six electrons, d orbital: ten electrons, f orbital: fourteen electrons

Question 33

Describe the structure of the atom based on modern atomic theory.

Answer 33

An atom is a complex arrangement of negatively charged electrons arranged in defined shells about a positively charged nucleus. This nucleus contains most of the atom's mass and is composed of protons and neutrons

Question 34

Name the three subatomic particles and given their relative sizes, location in atom, and charges. Which particles make up the mass of the atom?

Answer 34

Protons: nucleus, positive charge, neutrons: nucleus, neutral charge, electrons: negative charge, outside nucleus in shells; protons and neutrons make up the mass of an atom

Question 35

What is the periodic trend for atomic radius and reactivity?

Answer 35

decreases across a period: due to the increasing attraction between valence electrons and the nucleus across the period; Increases down a group:the atomic size is increasing, which causes the outer electron shells to be farther away

Question 36

Name the steps of the scientific method

Answer 36

1. Observe 2. ask a question 3. form a hypothesis 4. Experiment 5. analyze data 6. Conclusion 7. report findings

Question 37

Describe the properties of Alkali Metals

Answer 37

Group 1, Valence electrons 1. Extremely reactive, Reacts with water. Physical properties: Very soft, easily cut, good conductor of electricity

Question 38

Describe the properties of Alkali Earth metals

Answer 38

Group 2, 2 valence electrons. Chemical properties: highly reactive, but slightly less reactive than alkali metals will react to oxygen in the air. Physical properties: Higher melting points than the alkali metals

Question 39

Describe the properties of transition elements

Answer 39

groups 3-12 valence electrons vary chemical properties: -less reactive than alkali and alkali earth physical properties: - Most are solid at room temperature except Hg which is a liquid, good conductors of heat and electricity

Question 40

Describe the properties of other metals

Answer 40

between 13-16, valence electrons between 3-6. physical properties: good conductors of heat and electricity chemical properties: Some can react to form poisons Silver/grey in color, Malleable Easily lose electrons

Question 41

Describe the properties of non-metals

Answer 41

Non-metals hydrogen in group one, the rest 14-16 valence electrons between 1-7 chem properties: easily gains electrons phys prop: Exists at room temperature as a gas or solid poor conductors of heat and electricity

Question 42

Describe the properties of noble gasses

Answer 42

Group 18 8 valence electrons (except for He which has 2) chemical properties very unreactive (stable) Only Kr, Xe and Rn have been able to form compounds Physical properties colorless odorless tasteless

Question 43

Describe the properties of semiconductors (metalloids)

Answer 43

Semiconductors are the same as the metalloids group from the 4.2a notes. Metalloids have properties of both metals and nonmetals. Metalloids are used as semiconductors in electronics. Can be shiny or dull. Metalloids conduct heat and electricity better than nonmetals, but not as good as metals.