Chemistry final Flashcards
Mathematics
A study of relationships among numbers
includes measurements and calculations
Scientific method
A formal method for doing science
Technology
The application of scientific knowledge
Observations
Made by observing, describing, and measuring an event in nature
observations can be data
Qualitative and quantitative
Qualitative data
Descriptive information
Quantitative data
Numerical information
Hypothesis
A possible interpretation of observations
If (procedure), then (prediction), because (explanation)
Experiments
Tests that determine how well a hypothesis explains observations
Results may or may not accept the hypothesis
Theory
An explanation of facts and well-tested hypotheses
Can evolve over time as new knowledge is gained
Independent variable
X-axis
The variable that is purposefully changed in an experiment
Manipulated variable
There’s only 1 independent variable in an experiment
Dependent variable
Y-axis
The variable that is measured in an experiment
Manipulating the independent variable causes changes to the dependent variable
Responding variable
Constant variable
The variables that remain the same between the experimental and control groups
Control group
The group to which no changes have been made
Serves as a standard for comparison
Measurement
Length
Metric unit: Meter (m)
SI unit: Meter (m)
Tool: Metric ruler
Measurement
Volume
Metric unit: Liter (L)
SI unit: Cubic centimeters (cm^3)
Tool: Graduated cylinder
Measurement
Mass
Metric unit: gram (g)
SI unit: kilogram (kg)
Tool: Scale
Measurement
Temperature
Metric unit: Celsius (C)
SI unit: Kelvin (K)
Tool: Thermometer
Measurement
Time
Metric unit: Seconds (s)
SI unit: seconds (s)
Tool: Stopwatch
Exact numbers
Obtained by counting items or using a definition that compares two units in the same measuring system
Measured numbers
The numbers you obtain when you measure a quantity
Accuracy
How close the measurements are to the true or accepted value
Precision
How closely grouped a set if data is
Percent error
|experimental value-accepted value|/accepted value x 100
Density
A physical property of matter that compares the mass of a substance to the volume
Uses of density
- Identifying a specific substance
- Determining the purity of a substance
- Predicting if an object will sink or float in a liquid or air
Substances with high densities…
Particles that are closely spaced
Substances with low densities…
Have particles that are farther apart
Density formula
Density=Mass/volume
Volume of a rectangle formula
length x width x height
Displacement method
-A starting volume of water is measured
-The object is submerged into the sample of water
-The final volume of the object and water is measured
-The difference between the starting and final volume of the water, or the amount of displacement water, equals the volume of the irregularly shaped object
Democritus
All matter, plus space and time, is composed of tiny, indestructible units called atoms. Atoms are…
- Completely solid with no internal structure
-Differ in their sizes, shapes, and weights
John Dalton
Determined that each chemical element is composed of a unique type of atom
The atoms of an element are identical in their masses
Atoms of different elements have different masses
Atoms only combine in small whole number ratios to form compounds
J.J. Thompson
Atom composed of positively and negatively charged particles
Plum pudding model
Came up with electrons
Ernest Rutherford
Conducted the gold foil experiment from which he deduced the following about an atom:
Small regions in the center of the atom (nucleus) contain positive protons
Negative electrons occupy the region of space around the nucleus
Most of an atom is empty space
Niels Bohr
Developed a conceptual model of the atom using quantum theory in which electrons orbit the nucleus in fixed paths
Quantum mechanical model
Based on the work of several scientists
Electrons show wavelike behavior
It is impossible to know at any given time both the position and energy of an electron
Electrons are found in atomic orbitals or regions within an atom where electrons are likely to be 90% of the time
The atom
The smartest particle of an element that retains the characteristics of that element