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1. True or false: polar molecules share their electrons equally between atoms.
2. In water molecules, which atoms display a slight negative charge?a. Hydrogenb. Oxygen
3. The attraction between the hydrogen atom of one water molecule and the oxygen atom of another water molecule is called….a. An ionic bondb. A polar covalent bondc. A hydrogen bondd. Love
4. Water tends to stick to other substances. What is this property called?
5. Water and oil repel each other. That’s because oil is an example of a ______ substance.
Biology Journal 8/27/2014
2.2 Homework Quiz!
Biology Journal 8/28/2014
Which substance were you able to fit the most drops of liquid on top of a penny? What do you think could be some reasons for that?Why do you think the pepper was “afraid” of the soap?
Biology Journal 9/2/2014
What is a hydrogen bond?Where do we find hydrogen bonds between water molecules?Where do we find hydrogen bonds in DNA?
Hydrogen bonds form between polar molecules.• (+) side attracted to (-) side• a weak bond (it is easily broken)
The fact that water is polar, and forms hydrogen bonds explains it’s important properties to living things!
2.2 Water: Water is the medium (means of doing something) of life.
Nature of science: Use theories to explain natural phenomena—the theory that hydrogen bonds form between water molecules explains the properties of water.
Understandings: Water molecules are polar and
hydrogen bonds form between them. Hydrogen bonding and dipolarity
explain the cohesive, adhesive, thermal and solvent properties of water.
Substances can be hydrophilic or hydrophobic.
Applications and skills: Application: Comparison of the thermal properties of
water with those of methane (to understand the significance of hydrogen bonding). Probes can be used to determine the effect of different factors likely to influence cooling with water.
Application: Use of water as a coolant in sweat. Application: Modes of transport of glucose, amino acids,
cholesterol, fats, oxygen and sodium chloride in blood in relation to their solubility in water.
International-mindedness: There are challenges for the increasing human population in sharing water resources equitably for drinking and irrigation, electricity generation and a range of industrial and domestic processes. Theory of knowledge: Claims about the “memory of water” have been categorized as pseudoscientific. What are the criteria that can be used to distinguish scientific claims from pseudoscientific claims?
Topic 2: Molecular biology (21 hours)
2.2 Water
What are some things you remember about atoms?
What are these things called?What do they tell you?
Atomic Number• Number of p+
• Number of e-
Atomic Mass• Average mass of all
isotopes• Number of n0 and p+
(depending on the isotope)
Atomic Symbol• 1 or 2 letter
abbreviationElement Name
• There are many element names; xenon is the best name
What is this part called?What do you know about it?
Electron• Negative charge• Can be gained,
lost, or shared to form chemical bonds
Proton• Positive charge• Determines the
element
Neutron• Nutreal charge• Can be different
numbers (isotopes)
Orbitals• Determines if
an element will gain, lose, or share a specific number of electrons
What element is this?Nitrogen
The periodic table of elements tells you a lot about what’s in an atom.
Abundance of Elements on Earth cartogram
Abundance of Elements in the
Universe cartogram
What elements are most common in living things?
What are some things you remember about ions?
Ions are atoms that have gained or lost electrons. This gives them a (+) or (–) charge. Ionic substances are solids, but
most easily dissolve in H2O.
What do you know about covalent bonds?
A covalent bond forms when atoms share their extra valence electrons.
Electrons can be shared evenly (nonpolar) or unevenly (polar)
Polar molecules (AKA dipolar) do not share electrons evenly, giving it a positive (+) side and a negative (-) side. Water is very polar!
Hydrogen bonds form between polar molecules.• (+) side attracted to (-) side• a weak bond (it is easily broken)
The fact that water is polar, and forms hydrogen bonds explains it’s important properties to living things!
So, whenever you take a drink of water, just imagine those little Mickey mouse heads vibrating and bouncing off of each other, making and breaking hydrogen bonds, and interacting with other molecules that they come into
contact with.
Lipids are nonpolar molecules. They don’t have a charge on one side.
a saturated fatty acid
What does the prefix “hydro” mean?
What is a phobia?
What is a pedophile?
Hydro = “water”Like in hydroelectric dam
phile = “attracted to”Like in audiophile
phobia = “does not like”Like in arachnophobia
Hydrophobic = doesn’t like with water (it won’t mix with water). • Nonpolar
Hydrophilic = attracted to water (it will mix with water). • Polar
Rules of Attraction
Polar molecules• Attracted to polar• Repel nonpolar
Nonpolar molecules • Attracted to
nonpolar• Repel polar Molecules are attracted
to other molecules that are similar to them. Aww, just like people…
So, do you think…If something is polar, is it always hydrophilic?
If something is nonpolar, is it always hydrophobic?
YES(pretty much)
Properties of Water
Cohesion: Water is attracted to itself.• It makes hydrogen bonds!
Properties of WaterAdhesion: Water is attracted to other substances.
Water’s attraction to other substances is important in ground water, and how plants suck up that water!
Water is adhesive! It sticks to things like a shirt.
What is the “lake effect”?
Properties of WaterHigh Specific Heat: It takes a lot of energy to change water’s temperature.
Most metals have a low specific heat. It will heat up fast and cool down fast!
Technically, specific heat is the energy required to heat 1 kg of a substance 1°C
Properties of Water
Heat of evaporation: When water evaporates, this consumes a lot of heat.
Water’s high heat of evaporation of water related to water’s high specific heat. Hydrogen bonds attract water molecules to eachother, so they resist changing temperature or phase.
Properties of WaterSurface Tension: Energy is required to overcome the cohesion of water, and pass through the surface.
The surface tension of water is kind of like a game of Red Rover.
Properties of WaterGood Solvent: Water can dissolve many kind of substances.
Things like lake water, ocean water, and blood can dissolve a huge amount of nutrients.
Property of Water
How does the magnetic model show this property?
How could this property be beneficial to organisms in real life?
Hydrogen bonding
Hydrophilic
Surface Tension
Cohesion
Adhesion
Good solvent
High Specific Heat
Heat of Evaporation
In your notebook, make this table and fill it in:
What could be an example of something that has a high specific heat? A low specific heat?What are some ways that H2O’s specific heat help out living things?
Biology Journal 9/4/2014
No Journal today. Read these reminders, then get right to work on your mini-posters. • When you get a laptop, keep the
charger on the shelf it was on. When done, put your labtop back on the correct shelf and charge it!
• It’s due Monday! (it must be printed and turned in)
• Get a library pass to print it, or to work on it anytime between now and Monday.
