Unit 1 Flashcards
Chemistry
study of the composition, structure, properties, and reactions of matter.
Scientific Method
process of observation, inquiry, experimentation, and drawing conclusions
hypothesis
prediction of the expected outcome of the experiments designed to answer a given question
Scientific Method
Chemistry
study of composition, structure, properties, and reactions of matter
Matter
All substances that make up our world
Anything that has mass and occupies space
Can be pure substance or mixture
Natural chemical
Produced by nature
Synthetic chemical
Created in lab
Properties of Matter
characteristic useful for identifying a substance or object physical properties include:
– Size
– Color
– Temperature
Chemical properties include
-composition (what the natter is made of)
-reactivity (how the matter behaves)
-MP, BP
Scientific method
- Make observations about nature and ASK questions about what you OBSERVE
- Propose a hypothesis, which states a possible explanation of observations
- Several experiments may be done to test the hypothesis
- When the results of the experiments are analyzed, a conclusion is made as to whether the hypothesis may be true or false
- Observation
- Hypothesis
- Experiment
- Conclusion
Hypothesis is modified if
Modified if the results of the experiments do not support it
Physical quantity
Mass, volume, temperature, and density
Described by both a number and a unit
Physical quantity: a measurable physical quantity
Unit: a defined quantity used as a standard of measurement
Unit of Measurement and Abbreviations
1g = 1/1000 kg
1000 L = 1 m^3
Derived units
Represent the relationship between 2 measurable properties
Can’t be measured directly
Ex. Speed: meters per second (m/s) — length/ time
Density: grams per cubic centimeter (g/cm^3)—m/v
Mass
Measure of the amount of matter in object
Weight
Measure of the gravitational force that the earth or other large body exerts on an object
Mass units
1kg=1000g
1kg=2.20 lb
454g= 1lb
SI unit—kg used for larger masses
Metric unit—gram (g) used for smaller masses
Length units
1m = 100 cm
1m = 39.4 in
1m = 1.09 yd
2.54 cm = 1in
(Meter slightly longer than yard)
Volume units
SI unit: m^3
Metric unit: liter (slightly larger than a quart)
1 L =1000 mL
1 L =1.06 qt
946 mL = 1qt
Cubic centimeter
Volume of a cube whose dimensions are 1cm on each side
Cubic cm same volume as a milliliter, often used interchangeably
1cm^3 = 1cc = 1mL
1000 cm^3 = 1000 mL = 1 L
Prefixes and equalities
Can replace prefix with numerical value
Ex. Kilo = 1000 = 10^3
So
kilometer = 1000 meters (10^3 m)
Kiloliter = 1000 liters (10^3 L)
Kilogram = 1000 grams (10^3 g)
Physical quantities
Unit sizes can be modified using prefixes to refer to smaller or larger quantities
Prefixes for writing very large or very small numbers using scientific notation or units with appropriate numerical prefixes
Significant figures
-all nonzero digits and zeros between digits
-zeros at the end of a decimal number
-zeros that act as placeholders before digits
When one or more zeros in a large number are significant, place a decimal point after a significant zero at the end of a number.
300 m is = 3.0 × 102 m. (2 sig figs.)
300 m = 300. m or 3.00 × 102 m (3 sig figs)
Zeros at the end of large standard numbers without a decimal point are not significant.
400,000 g = 4 × 105 g (1 sig fig)
850,000 m = 8.5 × 105 m (2 sig figs)
Zeros at the beginning of a decimal number are used as placeholders and are not significant.
0.0004 s = 4 × 10−4 s. (1 sig fig)
0.0000046 g = 4.6 × 10−6 g. (2 sig figs)
Significant figures
Rounding off
Rounding off: addition and subtraction
calcuations cannot have more digits after the decimal point than the original measured values.
Density
m/v
Solids, liquids = g/cm^3 or g/mL
Gas = g/L
Note: 1mL =1 cm^3
Density
For most pure substances, the solid phase is the most dense because most substances contract when cooled and expand when heated.
– Water behaves differently; it contracts when cooled from 100 °C to 3.98 °C, but below this temperature it begins to expand again.
– Ice is less dense than liquid water
-Less dense substances will float on top of a more dense fluid
-Any substance with a density > water will sink in water.
Specific gravity
density of a substance divided by the density of water at the same temperature.
– At normal T, the density of water is very close to 1 g/mL.
– At normal T, the specific gravity of a substance is numerically equal to its density.
-can be measured using a hydrometer
Common equalities
Results
Results are experimental data that includes detailing all observations and measurable evidence.
All pure substances have
Density
Length
Metric and SI
meter (m)
Volume
Metric: liter (L)
SI: cubic meter (m^3)
Mass
Metric: gram (g)
SI: kilogram (kg)
Temperature
Metric: Celsius
SI: Kelvin (K)
Time
Metric and SI
Seconds
Giga
G
10^9
Mega
M
10^6
Kilo
k
10^3
Deci
d
10^-1
Centi
c
10^-2
Milli
m
10^-3
Micro
Mew
10^-6
Nano
n
10^-9
Pico
p
10^-12
Femto
f
10^-15
Unit conversions
1mL = 1cm^3
If it’s water 1mL = 1 gram
