1. Chemistry: a molecular science

2. science Science: an organized body of knowledge about nature
Uses problem solving process to create new ideas and help explain what we observe in nature
Problem solving requires recognizing a problem, proposing a solution, and testing it
Product of observations, common sense, and rational thinking

3. science
Chemistry: branch of science that studies matter and its transformations
Matter: anything that occupies space (including gas!)

4. Scientific method 2. Ask a question 3. Research
Method of organizing information and solving problems
1. Make an observation
Observations: a fact you determine using your 5 senses
Inference: something you reason out, not as reliable as observations
2. Ask a question
3. Research

5. Scientific method 4. Form a hypothesis
NOT an educated guess, a proposed explanation of a phenomenon
Hypotheses must be testable and falsifiable
No human lives forever – this statement cannot be falsified; you have to observe a human who lives forever.
5. Experiment (test the hypothesis)

6. Scientific method 6. Analyze your results 7. Draw a conclusion
8. Repeat work and share it with others
This is only one way of doing science! It doesn’t always follow the same process
Steps may not be in specific order

7. experiments
Experiment: a controlled procedure carried out to test a hypothesis
Variable: condition or trait you are testing (or changing)
Independent variable: this variable is manipulated by the experimenter, DOES NOT change in response to other variables
Dependent variable: the variable that changes in response to the independent variable, or being measured
Control group: does not receive the variable
Experimental group: exposed to the independent variable, then compared to the control group
Only ONE variable is tested in an experiment!!

8. experiments We want to know how sunlight effects a plant’s growth
Variable: amount of sunlight the plant receives
We could test this by placing one plant in a lot of sunlight, one plant in darkness, and leave a third plant at its usual place in the room
Control: plant with no sun
All plants need to get the same amount of water and the same type of soil, that way we know if sunlight helps the plant grow and not the other factors!

9. Laws & theories
After a hypothesis is tested several times, it is either accepted or rejected
Theory: a broad explanation for a wide range of phenomena.
Explains how nature works
Law: describes what nature does under certain conditions; mathematical relationships are usually involved
NO HIERARCHY involved! Hypotheses do not become theories, and theories do not become laws; none are “more true” than the others.

10. model Model: Any representation of an object or a system
Theories can sometimes be called a model because it helps to explain how a phenomenon works
Example: atomic model

11. Measuring Physical Quantities
Examples include length, time, mass, weight, volume, energy, temperature, heat, and density
Two major system units:
United States Customary System (USCS)
Used in U.S. for nonscientific purposes (height, length of the football field, etc.)
Système International (SI) or the metric system
Used in most other nations and by scientists all over the world, including those in the U.S.

12. The “SI” System Physical Quantity Metric Unit Abbreviation length
meter m
mass
kilogram kg
volume
liter L
temperature
kelvin/Celsius
K/C
time
second s
amount of substance
mole
mol

13. The Metric System Uses a decimal system
Easier to convert between units
All units are related to smaller or larger units by a factor of 10
Metric prefixes represent multiples of ten
Prefix: something added to the front of a word to change its meaning

14. Metric Prefixes Name Symbol Meaning Giga- G 1,000,000,000 Mega- M
Kilo- k
1,000
Hecto- h
100
Deka- da 10
(base)
Deci- d
0.1
Centi- c
0.01
Milli- m
0.001
DON’T MEMORIZE
Do an example of converting on board

15. conversions Converting from one metric unit to the other
Write down - G’’ M’’ k H Da base d c m
Put your pencil on the given unit (km)
Move the necessary number of spaces to get to the desired unit (m)
In this case, 3 to the right
G’’ M’’ k H Da base d c m
Then move the decimal point from the original quantity the same amount
1 km = 1,000 m

16. Mass vs. Weight
Mass: quantitative measure of how much matter a material object contains.
Measured in kg, g, mg
A gold bar that is twice as massive as another gold bar has twice as many gold atoms
Weight: gravitational force exerted on an object by the nearest, most massive body, such as the earth.
Measured in pounds and tons and depends entirely on the object’s location
You weigh less on the moon than you do on earth because the moon is less massive than the earth.

17. How to Measure Mass
If it is a “nonmessy” solid, simply weigh it on a scale
If it is a liquid or “messy” (a powder, greasy, etc.), use a weighing tray or a beaker.
Weigh the empty weighing tray or beaker and record its mass.
Add the object to the weighing tray or beaker and weigh it.
Subtract the mass of the empty tray or beaker to get the desired mass.

18. Scale Rules Gently place objects on scale.
Make sure the scale is clean prior to using it and when you are finished (wipe off excess powder, etc.)
Make sure that before you use it, the scale reads 0.00 g.
If it doesn’t, press on/zero before weighing your solid.

19. Volume Volume: The amount of space a material object occupies.
Si unit is the liter (L)
Measuring volume:
If it is a cubic solid, measure the length, width, and height, and multiply them. (l x w x h = v)
If it is a liquid, pour it in a graduated cylinder and read from the meniscus (low point of the curve)
Always place your eyes at the same level as the meniscus

20. Volume If the object is irregular:
Pour water into a graduated cylinder that is large enough to hold the solid. Read the volume of the water.
Place the solid into the water, but be careful to not spill any water.
Read the new volume.
Subtract the new volume from the old in order to get the volume of the solid.

21. Dimensional analysis
Also called factor-label method, involves expressing one unit as another, without changing its value.
Unit Conversion Factor: a fraction whose numerator and denominator are equivalent measures.
The goal is to introduce the unit you want in the answer while cancelling out the original unit

22. Dimensional analysis
A bucket holds 16 quarts. How many gallons of water will fill the bucket?
We want – gallons, cancel out – quarts
Use a unit conversion factor
16 quarts
1 gallon
16 quarts x gallons = =
4 gallons
4 quarts
4 quarts
Multiply across the top and bottom
Divide, cancel units that repeat

23. Dimensional analysis 4.5 hours!
If it takes John 16,200 seconds to complete his test, how many hours is that?
1 hour
16,200 s x min x hour
16,200 s
1 min =
60 s
60 min
3,600 s x min
4.5 hours!

24. Accuracy vs. Precision
Accuracy: how close you are to the actual answer
Precision: how close all of your answers are to each other
Accuracy is a measure of your lab technique, precision is a measure of your ability to duplicate what you just did

25. Dart Board Metaphor high accuracy, low precision
high precision, low accuracy
low accuracy, low precision
high accuracy, high precision

26. Measuring Accurately
Always report ALL numbers given on a digital readout (do NOT round)
Do NOT add or delete zeros to the end
Make sure your reading is stable
Always read your equipment as accurately as you can, take your time, get close to the instrument

27. Measuring Precisely If possible, always measure three times
If one measurement isn’t close to the others, always measure again
It’s a good idea to have your lab partner take the same reading as you to make sure you are reading it correctly