Chemistry
Name: ___________________________________________
Water Section B reading guide
Date: ______________________________ Period: _____
Section B.1
1. More than
70 percent of the Earth’s surface is covered by ocean water.
2. Define matter:
anything that occupies space and has mass.
3. What is the density of pure water?
4. Seawater has a
1.00 g/mL at 4 degrees Celsius
higher density than pure water. Explain your choice.
The dissolved ions contribute mass, which increases the density.
5. A 15 kg sample of pure water would have what volume? (show the DA work!!)
15 𝑘𝑔 𝑥
1000 𝑔
1 𝑚𝐿
𝑥
= 15,000 𝑚𝐿
1 𝑘𝑔
1.00 𝑔
Section B.2
1. Define mixture:
a combination of two or more substances. Each substance
must retain its own identity.
2. Was the foul water sample a heterogeneous or homogeneous mixture? Explain your answer.
It was heterogeneous because you could see small particles in
the sample.
3. Why is a sample of muddy water classified as a suspension?
In a suspension, the solids will settle to the bottom. Eventually
the mud will settle to the bottom.
4. How can a Tyndall test help in classifying matter?
The Tyndall test is used to distinguish between solutions and colloids. If
the beam of light can be seen, then it is a colloid.
5. Describe a water sample that contains dissolved sugar. Use the terms solute, solvent, and solution.
The overall sample is called a solution. The solute is the sugar,
and the solvent is the water.
6. An unknown solution conducts electricity. What must be present in the water?
Dissolved ions must be present.
7. Classify these sample of matter as either an element (E), compound (C), homogeneous mixture (HO), or
heterogeneous (HE) mixture.
chocolate chip cookie HE
oxygen gas E
ocean water HE
taco HE
a solid gold brick
E
carbon dioxide C
distilled water C
orange juice with pulp HE
table salt C
brass HO
potassium E
titanium E
silver E
water vapor C
clean, filtered air HO
liquid soap HO
or HE…explain!
Section B.3
1. What’s the difference between an element and a compound?
An element is a sample of matter made up of only one type of atom.
A compound is a sample of matter that contains molecules of different
atoms bonded together.
2. Chemists have identified more than
18 million compounds.
3. In the chemical formula NH4Cl, there are
1 N atoms, 4 H atoms, and 1Cl atoms.
Section B.4
1. Use a periodic table to list the symbols for the following elements:
Lead
Pb
Hydrogen
Helium
H
He
Sodium
Ca
Potassium
Calcium
2. Circle the subscript(s) in the formula
3. How many O atoms are in N2O?
Na
Tin
Sn
K
Gold
Au
Silver
Ag
Sulfur
N
Selenium
Nitrogen
Na2CO3.
1
4. Label the reactants and products in the reaction below:
2 Na + 2 H2O → 2 NaOH + H2
Reactants
5. There are 7 diatomic elements; list them.
Section B.5
1. Like charges
Products
H2 O2 N2 Cl2 Br2 I2 F2
repel.
2. Unlike charges
attract.
3. Describe the chemical attraction that is the “glue” that holds atoms together in a
compound.
The protons of one atom attract the electrons of another atom.
When this attraction is very strong, the electrons are removed
from the one atom, and ions form.
Section B.6
1. Define ion:
A charged atom. Cations are (+), anions are (-).
2. What does the symbol (aq) mean?
Aqueous. It is used to describe substances that are dissolved in water.
S
Se
3. Identify the following as either a cation or an anion.
Ca+2
H+
cation
cation
Cl-
anion
PO4-3
anion
Al+3
cation
O-2
anion
4. Explain the connection between the octet rule and the charge that an atom acquires.
Metal atoms have 3 or fewer valence electrons, and lose them to become
cations.
Nonmetals have 5 or more valence electrons, and gain the number they
need to have 8 total.
5. When sodium becomes an ion, what happens to the number of protons and electrons?
The number of protons doesn’t change. The number of electrons decreases by 1.
6. Define polyatomic ion:
a molecule that carries a charge.
Most are negatively charged.
7. List a few examples of polyatomic ions. Give their symbols, charges, and names.
Common ones are nitrate NO3-1, sulfate SO4-2, hydroxide OH-1, ammonium NH4+1 .
8. Name the one positive polyatomic ion on your chart.
ammonium, NH4+1
9. Write the correct formulas for these ionic compounds:
sodium bicarbonate
NaHCO3
magnesium chloride
MgCl2
lithium sulfate
Li2SO4
sodium nitride
Na3N
iron (III) chloride
FeCl3
silver nitrate
AgNO3
sodium carbonate
Na2CO3
aluminum sulfate
Al2(SO4)3
copper (II) sulfate
CuSO4
mercury (II) nitrate
Hg(NO3)2
calcium sulfate
CaSO4
lead (IV) nitrate
Pb(NO3)4
magnesium hydroxide Mg(OH)2
calcium hydroxide
Ca(OH)2
Section B.8
1. Even ion-free water is still “impure.” Which gases are commonly found dissolved in water?
Nitrogen gas, oxygen gas, carbon dioxide gas from the
atmosphere.
Complete Section Summary Questions 1, 5 through 8, 10 through 17, and 22.
For question 7, use the internet to research the physical properties.
Water section B textbook questions
1. The property of density explains why gasoline floats on water.
5 (a) Look for un-dissolved particles, then use the Tyndall test.
(b) If there are un-dissolved particles, it is a suspension. If the Tyndall
test is positive, with no un-dissolved particles, it is a colloid. A
solution will have a negative Tyndall test with no un-dissolved
particles.
6. (a) compound
(e) element
(b) element
(c) compound (d) element
(f) compound
(g) element (diatomic!)
7. H2O: colorless liquid at room temp. BP = 100°C.
d = 1 g/mL.
H2: colorless gas at room temp. BP = -252°C.
d = 0.00008 g/mL.
O2: colorless gas at room temp. BP = -183°C.
d = 0.0013 g/mL.
8. (a) i, ii, ,iv, vi
(b) iii, v
10. (a) H3PO4: 3 hydrogen, 1 phosphorus, 4 oxygen
(b) NaOH: 1 sodium, 1 oxygen, 1 hydrogen
(c) SO2: 1 sulfur, 2 oxygen
11. (a) NaHCO3 + HCl → NaCl + H2O + CO2
(b) C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
12. (a) 6 electrons
(b) 13 protons
(c) 82 electrons
(d) 17 protons
13. Only (c) is neutral.
14. (a) H
(b) Na+1
(c) Cl-1
(d) Al+3
15. Fe+3 will be attracted to c, repelled by b and d.
16. (a) neutral: ii, iii
anion: i
cation: iv, v
(b) anions gain electrons, cations lose electrons
17.
OH-1
PO4-3
S-2
Fe+3
Fe(OH)3
FePO4
Fe2S3
K+1
KOH
K3PO4
K 2S
Ca+2
Ca(OH)2
Ca3(PO4)2
CaS
22. All matter is made of “chemicals,” since all matter is made of atoms
of different chemical elements. “Chemical-free” is just a nonsense
thing to say!