Ch 2.2 Properties of Water
Vocabulary:
- adhesion
- cohesion
- hydrogen bond
- mixture
- solution
- suspension
Objectives:
How does the structure of water contribute to its unique properties?
Water has a unique shape- like a Mickey Mouse head.
The H (hydrogens) are bonded to the O (oxygen) by covalent or sharing bonds. This bond holds each individual water molecule together.
Water molecules are polar having a slight positive charge by the hydrogen end and a slight negative charge toward the oxygen end. Since opposites attract, each water molecule is attracted to another water molecule. The weak attraction of a positive hydrogen to a negative ion such as oxygen forms a hydrogen bond.
What do the red circles represent?
What do the white circles represent?
What charge is on the hydrogen end?
What charge is on the oxygen end?
Hydrogen bonds give water special properties.
1. Cohesion is an attraction between molecules of the same substance. Water “sticks” to itself.
This is why water beads up.
How many drops could place on your penny?
It also causes water to have surface tension.
You can float paperclips or insects can run across the surface of the water.
2. Adhesion is an attraction between water and different substances. This is what causes the meniscus or curve that you see in a graduated cylinder. The water is attracted to the cylinder
It also causes capillary action. This occurs when water is attracted to the side of a small glass tube and rises against gravity. This si also how water rises up roots to the stems and leaves of plants.
3. Heat capacity
water has a high specific heat which means that water resists changes in temperature.
4. Extremely high boiling point and extremely low melting point. This allows water to exist in all three states (solid, liquid, and gas on Earth)
5. Less dense as a solid than it is as a liquid
How does water’s polarity influence its properties as a solvent?
Why is it important for cells to buffer solutions against rapid changes in pH?
Video:
How We Got to Here: Clean water
http://video.pbs.org/video/2365347150/
Acids, Bases, and pH page 43
Vocabulary:
- pH scale
- acid
- base
- neutral
- buffer
The pH scale measures acidity ranges from 1-14.
- Acids have a pH of less than 7
- Neutral is 7
- Bases have a pH of greater than 7
Low pH values are strong acids while high pH values are strong bases.
- Which is the stronger acid: pH of 2.3 or pH of 6.7?
- Which is the stronger base: pH of 6.9 or pH of 13.2?
It is important to maintain homeostasis in living systems. To prevent sharp, sudden changes in pH, your body has buffers. Buffers react with strong acids and strong bases to prevent the changes in pH.
Cabbage Juice Lab
Use this link to see the various colors that cabbage juice changes with substances of various pH. We did a different lab in class.
https://www.erowid.org/archive/rhodium/worlock/ph.html
Chapter 2.3 Carbon Compounds
Objectives:
What elements does carbon bond with to make up life’s molecules?
Carbon can bond with many elements, including
- hydrogen
- oxygen
- phosphorus
- sulfur
- nitrogen
Living organisms are made up of molecules that consist of these and other elements
Review Video:
Crash Course Biology
Carbon
mhttp://www.youtube.com/watch?v=QnQe0xW_JY4
What are the functions of each of the four groups of macromolecules?
Carbohydrates
Lipids
Proteins
Nucleic Acids
Review Videos:
Crash Course Biology
mhttp://www.youtube.com/watch?v=H8WJ2KENlK0
Ch 2.4 Chemical Reactions and Enzymes
Vocabulary:
- chemical reaction
- reactant
- product
- activation energy
- catalyst
- enzyme
- substrate
What happens to chemical bonds during a chemical reaction?
- Chemical reactions are processes that change or transform one set of chemical into another.
- Elements that enter into a chemical reaction are called reactants and are shown of the left side of the arrow in a chemical equation.
- Elements or compounds that are produced in a chemical equation are called products are are shown on the right side of a chemical equation
example: hydrogen peroxide –> oxygen and water
What are the reactants? What are the products?
How do energy changes affect whether a chemical reaction will occur?
Chemical reactions that release energy often occur on their own.
Chemical reactions that absorb energy need an energy source to occur.
Activation energy is the amount of energy needed to start a chemical reaction.
Compare the amount of activation energy needed for the chemical reaction with and without an enzyme.
Why are reactions faster with an enzyme?
What role do enzymes play in living things and what affects their function?
Some chemical reactions that are necessary for life are too slow or have too much activation energy to make them practical for living organisms.
Enzymes are catalysts or substances that speed up the rate of chemical reactions. They do so by reducing the activation energy.
Review Animation: How enzymes work
What controls enzymes?
Enzymes can be controlled by:
- changes in temperature
- changes in pH changes
- activators
- inhibitors
Beano Lab
Lesson 1: What causes gas?
mhttp://www.youtube.com/watch?v=T5pvuAqPgko
Lesson2 : How Beano works.
mhttp://www.youtube.com/watch?v=LyBay7LKWZ0
Lesson 3: How Beano is different
mhttp://www.youtube.com/watch?v=kLHFTRKQhw4
Lesson 4 When to take Beano, and how much
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