Ch 3.2 and 2.4 Flashcards
Derived Units
- Carefully defined and can be derived from other base units
Base Units
- Carefully defined and cannot be derived from other units
Units before Metric System
- First known units: Indus Valley Civ.
- Egyptian length: Cubit
- Taking measurement was not possible without units
- Developing units made trade and commerce possible
- Developing universally understood units was difficult
- Units that did not work: Virgate, League, Rood, Jigger, Jack, Grain
In order to be unit, it must be….
- Clearly defined
- Reproducible
- It’s meaning will not change with time
- Easy to understand & convert between similar units
Metric System background
- 1791: French Academy of Scientist made Metric system
- Went into use in 1795
- Defined meter as 1/10000000 of the distance between Dunkirk and Barcelona
- Created platinum bar for other meters to be compared
Tera
- 10 to the 12th
- Symbol: T
Giga
- 10 to the 9th
- Symbol: G
Mega
- 10 to the 6th
- Symbol: M
Kilo
- 10 to the 3rd
- Symbol: k
Hecto
- 10 to the 2nd
- Symbol: h
Deca
- 10 to the 1st
- Symbol: da
No prefix means…
-One
Deci
- 10 to the -1
- Symbol: d
Centi
- 10 to the -2
- Symbol: c
Milli
- 10 to the -3
- Symbol: m
Mirco
- 10 to the -6
- Symbol: upside-down h)
Nano
- 10 to the -9
- Symbol: n
Pico
- 10 to the -12
- Symbol: p
What/ how was the Metric System revised?
- 1960: Metric System becomes SI system
- Meter became 1/ 299792458 seconds (distance light travels to be 1 meter)
- Created base units
7 Base Units during SI System
- Length: Meter (m)
- Mass: Kilogram (kg)
- Time: second (s)
- Electric current: ampere (A)
- Temperature: kelvin (K)
- Amount of substance: mole (mol)
- Luminous intensity: candela (cd)
Criticism of the SI System
- Derived units are not convenient size
- Base unit for mass= kilogram, which makes people thing that gram is the base unit.
Volume
- The space in which an object occupies
- L x W x H
Liter
- Non- SI unit
- 1,000 cm cubed is 1 Liter
Weight
- a force that measures the pull on a given mass by gravity
- effected by gravity
calorie
- cal
- Quantity of heat that raises the temperature of 1 g of water by 1 degree C
Temperature
- The measure of how hot or cold an object is
- When 2 objects come in contact heat moves from the object of higher temp to the one of lower temp
Celsius scale
- Freezing point : 0
- Boiling point: 100
Kelvin scale
- Freezing point: 273.15
- Boiling: 373.15
Absolute 0
- On the Kelvin scale
- When molecules almost stop moving, but don’t
- Equal to -273.15 C
Formula to turn Celsius into Kelvin
K= C+ 273
Formula to turn Kelvin into Celsius
C= K - 273
Density formula
Density= Mass/ Volume
Volume formula
Volume= L x W x H
Something will float on something else if…
-Its density is less than what it is floating on
Four signs of a chemical change
- Transfer of Energy
- Formation of Precipitate
- Gas production
- color change
Solid
- Rigid
- fixed shape
- fixed volume
- cannot be flattened
Liquid
- not rigid
- no fixed shape
- fixed volume
- Cannot be flatted
Gas
- Not rigid
- No fixed volume
- No fixed shape
- Can be flattened
Exothermic reaction
-A chemical reaction that releases energy in the form of light or heat
Endothermic Reaction
-A chemical reaction that absorbs energy
