1. Section 1-3: Measurement
Chapter 1 Introduction to Physical Science
Section 1-3: Measurement
Why do scientists use a standard measurement system?
What are the SI units of measurement for length, mass, volume, density, time, and temperature?

2. A Standard Measurement System
Chapter 1 Introduction to Physical Science
A Standard Measurement System
Using SI as the standard system of measurement allows scientists to compare data and communicate with each other about their results. SI units are based on multiples of 10. We will be using SI and other metric units.

3. Why do you think the US has not switched to the Metric System?
The SI system is considered to be the modern metric system.
It is considered a universal language for scientists, doctors, the military, and most countries.
The US is one of the only countries not on the metric system.
We use The English System which includes mph, feet, pounds, gallons, Farenheit, etc..
Why do you think the US has not switched to the Metric System?

4. Length The basic unit of length in SI is the meter (m).
Chapter 1 Introduction to Physical Science
Length
The basic unit of length in SI is the meter (m).
To measure something larger than a meter, scientist may use kilometers (km), which means one thousand.
To measure something smaller than a meter, scientists may use centimeters (cm), centi- means one-hundredth, or millimeters (mm), milli- means one-thousandth.

5. Consider a ruler
This ruler shows both Metric and English units for measuring length
The numbers on the top are centimeters
The tiny lines within each centimeter are millimeters.
Notice there are 10 mm in 1 cm. COUNT THEM!
How many mm are in 3 cm?
The numbers on the bottom are inches
Notice how much bigger 1 in is compared to 1 cm
There are 2.54 cm in 1 in
We will practice converting from Metric to Metric and from Metric to English later!

6. WEIGHT vs MASS Weight: Mass:
Your weight is a measure of the force of gravity on you.
The force of gravity may be more or less on other planets or moons than on Earth.
You would weigh about one-sixth of your Earth weight on the moon.
The newton (N) is the SI unit, the pound (lb) is the English unit.
Mass is the measure of the amount of matter an object contains.
Mass is not affected by gravity.
If you travel to the moon, the amount of matter in your body (your mass) will not change.
Scientists prefer to use mass rather than weight.
SI unit of mass is the kilogram (kg), but we will be using mostly grams (g) in this class.
WHY?

7. Volume Volume is the amount of space an object takes up.
Chapter 1 Introduction to Physical Science
Volume
Volume is the amount of space an object takes up.
The SI unit of volume is the cubic meter (m3), but we will often measure in Liters (L) or millileters (mL).

8. Volume of a liquid: Graduated cylinder mL
Meniscus- curved surface at top of liquid, always record measurements using bottom of meniscus

9. Volume of Rectangular Solid:
Volume of Irregular solid:
Example- Cereal box
Volume = Length x Width x Height
Remember to multiply numbers and units, so units will be cubed
Example units: cm3
Example- Rock
Submerge object in water in graduated cylinder and measure the displacement of the water
Let’s look at the example in your book on page 23 now

10. Density
Two objects of the same size can have very different masses. WHY???
Because different materials have different densities!
Density is mass per unit volume
So Density = Mass/ Volume
SI unit of density is kg/m3, other common units are g/cm3 and g/mL
Since density is made up of 2 measurements, it always has 2 units

11. Calculating Density Chapter 1 Introduction to Physical Science
Suppose that a metal object has a mass of 57 g and a volume of 21 cm3. Calculate its density.
Read and Understand
What information are you given?
Mass of metal object = 57 g
Volume of metal object = 21 cm3

12. Calculating Density Chapter 1 Introduction to Physical Science
Suppose that a metal object has a mass of 57 g and a volume of 21 cm3. Calculate its density.
Plan and Solve
What quantity are you trying to calculate?
The density of the metal object = __
What formula contains the given quantities and the unknown quantity?
Density = Mass/Volume
Perform the calculation.
Density = Mass/Volume = 57 g/21 cm3 = 2.7 g/cm3

13. Calculating Density Chapter 1 Introduction to Physical Science
Suppose that a metal object has a mass of 57 g and a volume of 21 cm3. Calculate its density.
Look Back and Check
Does your answer make sense?
The answer tells you that the metal object has a density of 2.7 g/cm3. The answer makes sense because it is the same as the density of a known metal–aluminum.

14. Calculating Density Chapter 1 Introduction to Physical Science
Practice Problem
What is the density of a wood block with a mass of 57 g and a volume of 125 cm3?
0.46 g/cm3

15. Chapter 1 Introduction to Physical Science
Density
The density of a substance stays the same no matter how large or small a sample of the substance is.
So a gold earring and a gold necklace will both have a density of 19.3 g/cm3

16. Sink or Float?
Knowing an object’s density allows you to predict whether it will sink or float.
If the object is less dense than the liquid, it will float.
If the object is more dense than the liquid, it will sink.
Problem: Water has a density of 1 g/cm3. Will an object with a density of 0.7 g/cm3 float or sink in water?
FLOAT!

17. Time The second (s) is the SI unit of time.
Chapter 1 Introduction to Physical Science
Time
The second (s) is the SI unit of time.

18. Chapter 1 Introduction to Physical Science
Temperature
Scientists use the Celsius and Kelvin scales to measure temperature. The kelvin (K) is the SI unit of temperature.