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

SIGNIFICANT FIGURES

Let’s Practice!

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?

ROUNDING OFF

If you have too many significant figures, you must round off to the correct amount

The same rounding rules apply Look at the number behind the rounding

number…5 or more, round up; 4 or less, leave it the same.