Experimental Design
List the 5 elements of a good experiment.
testable, repeatable, control, gradient, isolated variable
what are the two types of models?
physical, mathematical
what format should hypotheses be in?
If... then... because...
H2O2 -> H2O + O2
What are the reactants? What are the products?
Things you start with are the reactants, things you end with are products
What is a pH scale?
a scale that measure HYDROGEN ions (H+), 1-14, measures acidity
Chris is experimenting on flower growth. What could be an isolated variable he tests? How would he ensure the variable is isolated?
Ex: water added, sunlight received, fertilizer given etc
isolate by only testing one variable
Why would models be used by scientists?
to access things that are inaccessible
to observe and collect data
Why is repetition important?
consistent data = reliable data; to ensure not a one time fluke
What is a physical reaction? Chemical?
physical: change of state; no new substance
chemical: new substance; often change in color, temperature etc
what numbers on a pH scale are considered an acid? base? neutral?
1 >= acid > 7
neutral = 7
7 > base >=14
Katie is doing an experiment on if the diameter of pencil lead affects a student's handwriting. What would be a potential gradient for her?
ex: 0.3mm lead, 0.5mm, 0.7mm, 1.0mm, 2.0mm
two extremes, things in between
explain the advantages and disadvantages of physical models.
advantage:
hands on, easy to manipulate, cheaper
dis:
may not be accurate, over simplified
5 characteristics of living things?
made of cells, reproduce, grow and develop, obtain and use energy, respond to environment
What is metabolism? (What are the two types of reaction that make up metabolism?)
cat = breakdown of larger components
ana = synthesizing or building larger components
What ions do acids contain more of? bases?
acids: H+
bases: OH-
Remmie wants to test if a new energy candy is effective. There are two groups in the experiment. The first group receives the energy candy, the second group just receives a regular candy without the energy substance. What is the purpose of the second group? What do we call this group?
Control group. Tests if the candy was effective, if both groups show the same results, then the candy was not effective. Control groups test is the experiment works.
Explain the advantages and disadvantages of a mathematical model.
adv:
predict future events, easily repeatable, more control over variables
dis:
limited randomness, may give unnatural results, may be oversimplified
What is a chemical compound? a solution?
Compound: chemical combination of two or more elements
solution: solute + solvent
what are the four macromolecules? which one is an enzyme?
carbohydrates, lipids, proteins, nucleic acids
enzyme = protein
review CHO, CHON, CHONP with them
What happens when you add an acid to a base? What happens to the ions? pH number?
Draw what happens to the ions.
neutralize, the H+ from the acid will bond with the OH- from the base and create water H20, a neutral substance. The pH will drop.
Design an experiment using the five elements of a good experiment for testing the effectiveness of a new energy drink on the ability for students to stay awake.
testable? (cause and effect) repeatable? (detailed procedure?) isolated variable? gradient? control?
How is our ecosystem a model? What type of model is it? How is this important?
It is a smaller scale ecosystem that we can observe and take data on. It is a physical model. This gives us an idea of what a large scale ecosystem is like because we would not be able to observe a full scaled ecosystem.
Christian wrote the following hypothesis:
If I feed my adult pet turtle 2 scoops of turtle feed every 2 days, then it will grow 1cm (measure from head to tail) in one month because that is what my mom told me.
Evaluate and rewrite the hypothesis.
if/then/because
makes sense
cause and effect
tested with measurements
easy to understand
just needs a better source.
If... because nutrients from the food will help the turtle grow, adult turtles eat less, especially in the winter. ACCORDING TO... (cite)
Do temperature and pH of an environment affect enzymes? Why? How did we test for this in lab?
YES! Enzymes have a site where they take the reactants to create the products. If the temp/pH is not ideal, the enzyme can deform and no longer take the reactants (slower or no reaction rate).
We tested ideal pH of our enzymes by testing a gradient and only changing one var (pH).
What is a buffer? Why is it important? What happens if there is no buffer?
Draw an acidic solution with a buffer. Draw what happens when you add a strong base.
buffer is a weak acid or base that is in a solution that will mix with any added acid/base to neutralize it so that the pH of an environment can be maintained relatively similar. Without a buffer, the pH may drop or spike drastically with the addition of a strong acid/base.