Chemistry FINAL!!!!! Flashcards
Mulipying and dividing Sigfigs
Do not round until the end
Count number of sigfigs in each number
Find the number with the lowest amount of sigfigs.
Sigfig rules
All non zero digits are significant.
Zeros between sigfigs are significant. EX (0.504)
Leading zeros are not significant
Trailing zeros after a decimal place are significant EX.(4.0)
97(2) and 97.00(4) are different
Trailing zeros can be significant, if a deciaml is shown.
Exact numbers have an infinite amount of sigfigs.
All digits that compromis “n” are significant Ex. (10^x is not significant).
Adding and subtracting sigfigs
Do not round until the end
Find number with least amount of decimal places.
Density equation
Density = Mass divided by volume
Physical property
Characteristic of a substance that can be observed without changing it to something else.
Chemical property
Characteristic of a substance that can only be observed if it is changing
Extensive property
Change based on how much matter we have
Ex. Volume, shape, mass
Intensive property
Stays the same no matter how much matter we have
Ex. Color,texture, boiling/freezing point, density
Mixture
Made of two or more pure substances
Element
Substances that cannot be seperated into simpler substances by chemical means
Compound
A pure substance composed of two or more elements whose composition is constant
Law of definite proportions
A pure substance will contain same elements in same proportions by mass
Alloy
- Made of two or more metals, or a metal and a nonmetal (must be solid at room temp)
- Melt solid components and allow to mix/dissolve
- To identify must know types of metal/solid used.
Subscript
Say how many atoms of a certain element are present
If there are no subscripts then there is only 1 atom of that element.
Coefficient
Determines how many is needed
_ c2h4 + 3 o2 –> 2co2 + 2h20
c = 2
h = 4
0 = 6
Law of conservation of matter/mass
Matter cannot be created or destroyed
During chemical reactions, no matter is lost/gained
Elements you start with, you end with
Physical changes
Type of matter that has not changed
* mas, shape, volume, state of matter
Change is often reversible
*phase change, shape
Chemical changes
Type of matter that has changed into another matter
Change is often not reversible
* combustion
Generally, if the observalbe intensive properties have changed, then a chemical change has occured.
Reactants
Chemicals you start with
* CH4 + 02 —->
[________]
Reactants
Synthesis equation
A+B ——> AB
Decomposition equation
AB —–> A + B
Single replacement equation
AB + C ——> BC + A