Unit 2 Test Review Topics Include: Nature of Science Basic Chemistry Properties of Water Macromolecules Chemical Reactions and Enzymes

Nature of Science A. The experimental method What are the multiple steps of this method in sequence? 1. Problem 2. Hypothesis 3. Design Experiment 4. Do experiment 5. Analyze data 6. Form conclusion What does each step accomplish? Problem = purpose behind exp. Hypothesis = prediction being tested. Design = variables distinguish a plan. Analyze = Makes sense of the data. Conclusion = support or not support hypothesis.

Nature of Science Identifying variables – control, independent, dependent, constants Independent = manipulated or influenced variable Dependent = measured or results of experiment Control group = no independent variable, compare results to this Constants = always the same in all test groups, ensures reliability of info Types of data – qualitative / quantitative Qualitative = descriptions and characteristics found in experiment Quantitative = the measured amount found in the experiment Can you make / use graphs to describe different data? Yes. You should be able to. How do you read a bar graph? A line graph? A data table?

Nature of Science B. What is science? Science is the systematic study of the world around us that helps us explain the natural phenomena observed. Collections of theories (theories highly supported claims, not disproven) and laws (understood facts of things that occur in science) How is it different from a pseudoscience or non-science? Pseudo science = “fake science” – not based on empirical evidence Non-science = anything that isn’t a science

Atoms, Ions, and Molecules Distinguish between atoms, elements, and compounds Atoms – smallest unit of matter Elements – unique types of atoms that exhibit special properties Compounds – combination of different atoms that gives new properties to those involved Identify the 3 different kinds of bonds and how they occur. Covalent – sharing of electrons (strongest bond) Ionic - giving up or gaining electrons (fairly strong) Hydrogen – attraction between molecules of different charges (weak)

Atoms, Ions, and Molecules Define an ion and identify 2 examples. NaCl – salt, Cl has a negative charge, Na has a positive charge. Define a compound and identify 2 examples H20 , C6H12O6

Special properties of water (BTW all these properties are caused by hydrogen bonds) Draw the molecular structure of 1 water molecule. Define polarity An unequal sharing of electrons causes one side of a molecule to have a positive side, and a negative charge for the opposite side.

Special properties of water Define hydrogen bonding Two polar molecules are attracted to the oppositely charged ends of each other Compare and contrast cohesion and adhesion and give an example of each. Cohesion and adhesion both use hydrogen bonds to cause water molecules to “stick” to other places, but cohesion is only between water molecules Compare and contrast solute and solvent. Solutes are dissolved in a solution, Solvents do the dissolving in the solution.

Special properties of water Explain these properties of water (you should know all of these) Hydrogen bonding = weak bonds cause water to stick to things Polarity = two oppositely charged sides of the same molecule Cohesive = water sticks to water molecules Adhesive = water sticks to things other than water High specific heat = takes a lot of energy to change the temp of water Expands when frozen = molecules evenly distribute when frozen Why is water considered the a Universal Solvent? It’s usually the solvent in most solutions How do some properties of water play a role in living things? Capillary action, surface tension

Carbon-based molecules AKA: macromolecules or biological molecules Define a monomer = single piece of a more complex molecule Define a polymers = larger molecule formed from single pieces Why is carbon used so extensively in creating macromolecules It can make up to 4 covalent bonds, making it a great backbone for molecules What are the four macromolecules and what are their functions? Carbs = short term energy ; Protein = do all cellular activities ; Lipids = store long term energy ; nucleic acids = stores genetic info What kinds of foods do we find certain macromolecules in? Protein = meats/beans ; carbs = plants ; lipids = saturated are from animals, unsaturated from plants ; nucleic acids = everything that was ever alive

Chemical Reactions Draw a simple chemical reaction and indicate the products and reactants. Reactants Products C6H12O6 + O2  H2O + CO2 NaCl  Na+ + Cl-

Enzymes What is activation energy? The amount of energy required to start a chemical reaction B. What does a catalyst do for chemical reactions? Speeds them up by lowering activation energy C. What is an enzyme and what do they do for living things? Usually a protein that acts as a catalyst. Used for digestion, replication, growth, etc… D. How is the structure of an enzyme important? Lock and key model – shape of enzyme determine what substrates can fit to the active site, this helps chemical reaction occur. E. What 3 things can affect enzyme activity Concentration, pH, temperature

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