BASICS OF PHYSICAL SCIENCE
Scientific Method, Units of Measurement, Scientific Notation, Significant Figures
EQ: WHAT IS PHYSICAL SCIENCE? The sciences can be divided into 2 main
branches: _____________ and _________ Natural science is divided into earth, life and
physical sciences Physical science covers non-living things These areas include ____________ and
________________ Chemistry is the study of matter and its
properties Physics is the study of matter and energy and
interactions between forces and motion
PHYSICAL SCIENCE We use the scientific method to answer
questions scientifically The scientific method consists of the following
steps: ____________________ ____________________ ____________________ ____________________ ____________________ ____________________
Matter
Throughout the course, we’ll focus on _____________.
Matter is anything that has 2 major properties: ______________ and ____________.
Anything that has mass and takes up space is matter.
This means that almost everything is matter except things like light, sound, thoughts, feelings and ideas.
Properties of Matter
________________ are the characteristics we use to describe matter.
Properties can be _____________ or ______________. Chemical properties are those characteristics that can
only be detected with a chemical reaction like pH, reactivity and flammability.
Physical properties are those that can be easily observed like color, shape, texture, odor and density.
We’re going to use density to demonstrate some basic information that you need to know.
Density
_______________ is how much matter is in a volume of a substance.
Density tells us if an object will float or sink. “Light” objects (with less matter) float. “Heavy” objects (with more matter) sink. Examples of “light” objects: Examples of “heavy” objects:
Float or Sink? Will these items float or sink? A golf ball? A ping pong ball? Why? Even though they are about the same size, the golf
ball is heavier and therefore has a greater mass:volume ratio.
Can of Coke? Can of Diet Coke? Why the difference? The Diet Coke does not have the sugar that the
regular Coke does and so it is less dense and therefore floats.
Density Calculations
Density = mass/volume D = m/V Units: g/cm3 or g/mL
NOTE: (A cubic centimeter is the same as a milliliter.)
You can use the triangle to find any unknown as long as you have two of the items.
Just cover the item that you’re looking for and you will have the formula to calculate it.
DENSITY
MASS
VOLUME
÷
x
Density Calculations
A piece of tin has a mass of 16.52 g and a volume of 2.26 cm3. What is the density of tin?
Density = mass/volume Mass = 16.52 g Volume = 2.26 cm3
Density = 16.52 g/ 2.26 cm3 Density = 7.31 g/cm3
Questions?
PHYSICAL SCIENCE In order to communicate your findings to
others, you must use a common language Parts of this language include:
_____________________ Used to write very large or very small numbers in a
shorter way
_____________________ Numbers without units don’t mean a thing!
_____________________
When measuring items there are only so many digits that actually mean something.
EQ: HOW DO YOU EXPRESS NUMBERS IN SCIENTIFIC NOTATION? Move the decimal after the first number (NOT A ZERO!);
round off to 2 decimal places Your first number should be between 1 & 9! Keep track of the number of places you moved the decimal The number of decimal places will become the exponent for
the 10 If you moved the decimal right, the exponent is negative; if
you moved the decimal left, the exponent is positive Example: 123,456,789 Example: .000123456789 More Practice! Even More Practice!
EQ: HOW DO I ENTER NUMBERS IN SCIENTIFIC NOTATION INTO MY CALCULATOR?
Find your key w/EE Key in the decimal Press whatever it takes to get the EE on your
screen (could be EE or 2nd EE) Key in the exponent DO NOT KEY IN THE x10 part…it will throw your
entire calculation off.
SCIENTIFIC NOTATION
When performing calculations with numbers in scientific notation: Multiplication: Multiply the numbers , then, add the
exponents Example: (1.1 x 103 )(2.4 x 103) =
Division: Divide the numbers, then subtract the exponents (numerator – denominator) Example: (2.6 x 106)/(1.1 x 103)=
More Practice Even More Practice!
EQ: HOW DO WE DETERMINE WHICH UNITS TO USE FOR VARIOUS MEASUREMENTS? Scientists use the International System of Units or
the SI units The SI units are based on the metric system Every type of measurement has a base unit
Length: meter (m) Mass: kilogram (kg) Temperature: kelvin (K) Time: second (s)
Units are VERY IMPORTANT! Numbers without units are meaningless!
METRIC PREFIXES To accommodate very small measurements or very
large measurements, we can add prefixes to the base unit
A metric prefix tell us how many times a unit should be multiplied or divided by 10
Common metric prefixes: _____________ (1,000 or 1 x 103) _____________ (100 or 1 x 102) _____________ (10 or 1 x 101) _____________ (0.1 or 1 x10-1) _____________ (0.01 or 1 x 10-2) _____________ (0.001 or 1 x 10-3)
EQ: HOW DO I CONVERT UNITS WITH PREFIXES?
Technically, you have to divide or multiply by the unit of ten, but there is an easier way….
King Henry Died By Drinking Chocolate Milk The first letter of each word in the sentence above
stands for the common metric prefixes K = kilo H = hecta D = deka B = BASE D = deci C = centi M = milli
CONVERTING BETWEEN METRIC PREFIXES
To convert from one to another, simply count the number of places you have to move to get from one to the other
Move your decimal the same number of places and in the same direction.
Example: Convert 0.005676 kilometers to millimeters
K H D B d c m
EQ: WHAT ARE SIGNIFICANT FIGURES AND WHAT IS THEIR IMPORTANCE?
When we use measurements in calculations, our answer can’t be anymore precise than the original calculations
Precision is a measure of how exact a measurement is….more numbers
Take the value of pi for example: Pi = 3.14159265 Pi = 3.14 When looking at this, the first value is more precise
than the second.
SIGNIFICANT FIGURES
Scientist use _______________ to determine how _______________ a measurement is.
Significant digits in a measurement include all of the _______________ plus one _______________ .
FOR EXAMPLE…
Look at the ruler below
What would be the measurement in the
correct number of sig figs? _______________
THE SAME RULES APPLY WITH ALL INSTRUMENTS
The same rules apply
Read to the last digit that you know
Estimate the final digit
LET’S TRY GRADUATED CYLINDERS
Look at the graduated cylinder below
What would be the measurement in the correct number of sig figs?
_______________
RULES FOR SIGNIFICANT FIGURES RULE #1
All non zero digits are ALWAYS significant How many significant digits are in the
following numbers?
274 25.632 8.987
_____________ _____________ _____________
RULE #2
All zeros between significant digits are ALWAYS significant
How many significant digits are in the following numbers?
504 60002 9.077
_____________ _____________ _____________
RULE #3
All FINAL zeros to the right of the decimal ARE significant
How many significant digits are in the following numbers?
32.0 19.000 105.0020
_____________ _____________ _____________
RULE #4
All zeros that act as place holders are NOT significant
Another way to say this is: zeros are only significant if they are between significant digits OR are the very final thing at the end of a decimal
FOR EXAMPLE
1) 0.0002 2) 6.02 x 1023
3) 100.000 4) 150000 5) 800
1) _____________ 2) _____________ 3) _____________ 4) _____________ 5) _____________
How many significant digits are in the following numbers?
RULE #5
All counting numbers and constants have an infinite number of significant digits
For example: 1 hour = 60 minutes 12 inches = 1 foot 24 hours = 1 day There are 30 students in the class
HOW MANY SIGNIFICANT DIGITS ARE IN THE FOLLOWING NUMBERS?
1) 0.0073 2) 100.020 3) 2500 4) 7.90 x 10-3 5) 670.0 6) 0.00001 7) 18.84
1) _____________ 2) _____________ 3) _____________ 4) _____________ 5) _____________ 6) _____________ 7) _____________
SIGNIFICANT FIGURES
If you have two calculations that you’re using, your answer can’t have more numbers than your original measurements
If I multiply 2.3 and 3.1, I end up with 7.13. This answer is not valid because it has 2
decimal places when my original measurements only had 1.
This is where significant figures come into play
SIGNIFICANT FIGURES
Significant figures are all the digits that are known in a measurement
When counting significant figures, every digit 1-9 counts
Zeros are the funny ones! Zeros are only significant in two situations:
When between two other significant figures When it is the last number after the decimal
CALCULATIONS WITH SIGNIFICANT FIGURES
When adding or subtracting, the final answer can have no more significant figures after the decimal than the one with the least amount
150.0 g H2O + 0.507 g salt 150.5 g solution You can only have one number after the decimal
because the mass of water only has one
CALCULATIONS WITH SIGNIFICANT FIGURES
When multiplying or dividing, you can have no more total significant figures in your answer than you have in your measurement that contains the least amount.
The total number of sig. figs. count here…not only those behind the decimal!
If you were to multiply 1.23 by 4.5, you could only have 2 significant figures in your answer
What if you multiplied 67.8 by 9?