Question

sch3u
chemistry review
1.a) define the term \pure substance\ and give one example.
date:____
b) define the term \mixture\ and give one example.

1. classify each of the following as elements, compounds, homogeneous mixture or heterogeneous mixture.

oxygen gas:
salt and pepper:
pure water (h₂o):
grape koolaid:
copper (cu):
air:
oil and water:
ammonia (nh₃):
steel:
methane (ch₄):

1. identify each of the following changes as physical or chemical and explain your choice:

a) iron rusts when exposed to air:
b) sugar dissolves in water:
c) gasoline burns in an engine:

1. list one property and one example of each of the following types of elements:

property
example
a) alkali metal:
b) halogen:
c) noble gas:

1. a) where are metals found on the periodic table?

b) where are non - metals found on the periodic table?

1. complete the following table for neutral atoms:

atomic number	mass number	# protons	# electrons	#neutrons	standard symbol
11				12
	56	26

1. complete the following chart

bohr - rutherford diagram	sulfur (atomic number 16)	potassium, atomic number 19
lewis dot diagram
charge of most common ion

Explanation:

1.a) A pure substance is a material that has a fixed or definite composition. For example, gold (Au) is a pure substance as it consists of only gold atoms.
1.b) A mixture is a combination of two or more substances that are not chemically combined. An example is a salad, which has different vegetables combined together.

1. Oxygen gas: Element; Salt and pepper: Heterogeneous mixture; Grape koolaid: Homogeneous mixture; Air: Homogeneous mixture; Ammonia ($NH_3$): Compound; Pure water ($H_2O$): Compound; Copper (Cu): Element; Oil and water: Heterogeneous mixture; Steel: Homogeneous mixture; Methane ($CH_4$): Compound.

3.a) Chemical change. Iron reacts with oxygen in air to form iron - oxide (rust), a new substance is formed.
3.b) Physical change. Sugar dissolves in water, but no new chemical substance is formed, just a sugar - water solution.
3.c) Chemical change. Gasoline burns in an engine, reacting with oxygen to produce carbon - dioxide, water and energy, new substances are formed.
4.a) Alkali metal property: Highly reactive with water; Example: Sodium (Na).
4.b) Halogen property: Highly reactive non - metals; Example: Chlorine (Cl).
4.c) Noble gas property: Unreactive; Example: Helium (He).
5.a) Metals are found on the left - hand side and in the middle of the periodic table.
5.b) Non - metals are found on the right - hand side of the periodic table.

1. For atomic number 11: Mass number = 23 (11 protons + 12 neutrons), # protons = 11, # electrons = 11 (neutral atom), # neutrons = 12, Standard symbol: $^{23}_{11}Na$; For mass number 56 and # protons 26: Atomic number = 26, # electrons = 26 (neutral atom), # neutrons = 30 (56 - 26), Standard symbol: $^{56}_{26}Fe$.
2. For sulfur (Atomic number 16): Bohr - Rutherford diagram: 2 electrons in first shell, 8 in second shell, 6 in third shell; Lewis Dot Diagram: 6 dots around S; Charge of most common ion: - 2. For potassium (Atomic number 19): Bohr - Rutherford diagram: 2 electrons in first shell, 8 in second shell, 8 in third shell, 1 in fourth shell; Lewis Dot Diagram: 1 dot around K; Charge of most common ion: + 1.

Answer:

1.a) A pure substance has a fixed or definite composition. Example: Gold (Au).
1.b) A mixture is a combination of two or more substances that are not chemically combined. Example: Salad.

1. Oxygen gas: Element; Salt and pepper: Heterogeneous mixture; Grape koolaid: Homogeneous mixture; Air: Homogeneous mixture; Ammonia ($NH_3$): Compound; Pure water ($H_2O$): Compound; Copper (Cu): Element; Oil and water: Heterogeneous mixture; Steel: Homogeneous mixture; Methane ($CH_4$): Compound.

3.a) Chemical change. Reason: A new substance (iron - oxide) is formed.
3.b) Physical change. Reason: No new chemical substance is formed.
3.c) Chemical change. Reason: New substances (carbon - dioxide, water) are formed.
4.a) Property: Highly reactive with water. Example: Sodium (Na).
4.b) Property: Highly reactive non - metals. Example: Chlorine (Cl).
4.c) Property: Unreactive. Example: Helium (He).
5.a) Left - hand side and middle of the periodic table.
5.b) Right - hand side of the periodic table.

1. For atomic number 11: Mass number = 23, # protons = 11, # electrons = 11, # neutrons = 12, Standard symbol: $^{23}_{11}Na$; For mass number 56 and # protons 26: Atomic number = 26, # electrons = 26, # neutrons = 30, Standard symbol: $^{56}_{26}Fe$.
2. Sulfur: Bohr - Rutherford diagram: 2, 8, 6; Lewis Dot Diagram: 6 dots around S; Charge of most common ion: - 2. Potassium: Bohr - Rutherford diagram: 2, 8, 8, 1; Lewis Dot Diagram: 1 dot around K; Charge of most common ion: + 1.