Lesson 2.3 Honors Biology
____________ is a difference in electrical charge between different parts of the same molecule
polarity
a difference in electrical charge within the same molecule
polarity
In a water molecule, the hydrogen atoms have a ____________ charge
positive
A mixture of two or more substances with the same composition throughout is a ___________
solution
has the same composition throughout
solution
Water's ____________ gives it unique properties that help explain why it is vital to all living organisms
structure
Pure water has a pH of 7
true
Earth is sometimes called the
"water planet," because almost 75% of its surface is covered with water
Bases have a pH lower than 7
False
Enzymes in the small intestine need an acidic environment in order to work
False
Hydrogen bonds are very strong bonds
False
Hydrogen bonds cause water to have a relatively high boiling point of 100°F
False
Soap is very acidic
False
The hydrogen atoms in a water molecule attract electrons more strongly than the oxygen atom does
False
Hydrogen bonds explain why water molecules stick together, hydrogen bonds cause water to have a relatively high boiling point, hydrogen bonds also cause water to expand when it freezes
How do hydrogen bonds affect water's properties?
Attracts electrons more strongly than the hydrogen atoms, has a slight negative charge, binds to a hydrogen of another water molecule through a hydrogen bond.
The oxygen in a water molecule
A water molecule has positive and negative parts to it
True
Acids have a pH lower than 7
True
An ion is an electrically charged atom or molecule
True
Lemon juice is a stronger acid than orange juice
True
The stomach is a very acidic environment
True
Water is a chemical
True
Water is a reactant in photosynthesis
True
Water is released during cellular respiration
True
Which of the following is an example of a solution?
a glass of orange juice
A(n) ____________ has a pH lower than 7
acid
has a pH less than 7
acid
pH is a measure of the ____________ of a solution
acidity
has a pH more than 7
base
____________ is slightly basic with a pH just above 7
blood (soap, saliva)
100°C is water's ____________ point
boiling
for water, 212°F or 100°C
boiling point
A solution with a lower concentration of hydronium ions than pure water
can have a pH of 6.5
Water molecules are held together by ____________ bonds
hydrogen
holds water molecules together
hydrogen bond
OH-
hydroxide ion
Where is most of the freshwater found?
in icecaps, glaciers and inland seas
Which is the strongest acid?
lemon juice
Ice floats on water because ice has a ____________ density
lower
In water, the ___________ atom attracts electrons more strongly than the ___________- atoms do
oxygen, hydrogen
a measure of the acidity of a solution
pH
a range from 0 to 14
pH scale
an organ that secretes a strong base into the small intestine
pancreas
needs an acidic environment to work
pepsin
Water is essentially neutral, with a pH of ____________
7
photosynthesis
6CO2 + 6H2O + energy --> C6H12O6 + 6O2
