Experimental Design Vocab
independent variable (IV)- the variable that is manipulated/deliberately changed/tested
dependent variable (DV) - the variable that is measured/observed
depends on IV
changes in response to IV
constants - factors that do not change during an experiment
control - group used to compare to the tested variable
exposed to the same conditions as the experimental group, except for one independent variable
types of graphs
pie graphs - used to show parts of a whole
bar graphs - used to compare quantities
scatter plot - used to show the change in one piece of information as it relates to another change
Analyzing scatter plot
Best fit line (trendline)
Purpose is to determine the trend or relationship between the variables
mathematical equation
if linear, usually in y = mx + b form
m = slope
3) linear regression (R2 value)
measures level of correlation between variables
1 = strong correlation
Interpolate vs. Extrapolate
extrapolate - extending the graph, along the same slope of the best fit line, above or below measured data
i.e. using the mathematical equation
interpolate - predicting data between 2 points on the best fit line
Matter
Anything that has mass and takes up space
Can exist in 3 different states
Solid: particles in a solid are closely packed and held tightly in place.
Liquid: particles are still close together but can move past each other, allowing the liquid to flow.
Gas: Particles are well separated and move freely.
classifying and identifying matter
Pure Substances: have distinct properties and composition. - two types of substances:
Elements: cannot be decomposed into simpler substances (represented by a symbol on the periodic table).
Compounds: can be decomposed into simpler substances (is a combination of elements - multiple symbols) EX: H2O
Mixtures: Exhibit the properties of the substances that make them up (multiple substances). Homogeneous: Have the same composition throughout a sample (AKA: liquid). Heterogeneous: vary in composition throughout a sample (EX, dinner salad).
Compare and contrast physical property vs. a chemical process. Give and identify examples of each.
Physical Properties:
can be observed w/ senses.
can be determined w/o destroying matter
Ex: boiling point, density, mass, or volume
Chemical Properties”
indicates how a substance reacts (changes chemically) with something else.
Matter will be changed into a new substance after the reaction
Ex: flammability, corrosiveness, or reactivity with acid
Compare and contrast physical changes vs. chemical changes.
Signs of a chemical change: a new odor, color change, gas production, precipitate (formation of a solid), temp. change (without explicitly adding/removing energy), evolution of gas (bubbles).
Apply conservation of mass to any chemical or physical change. List various forms of energy, explain the role of energy in a chemical change.
In a chemical change…
Law of Conservation of Mass: matter cannot be created or destroyed it can only change form (rearrange).
Law of Conservation of Energy: energy can not be created or destroyed. - many chemical changes either cause energy to be released (heats up) or absorbed (cools down)
Forms of energy: chemical, genetic, nuclear
Describe the properties and units of length, mass, volume, density, temperature, and time.
length - mesures distance - meter (m)
mass - amount of matter - kilogram (kg)
volume - space an object occupies - liter or cubic meter (mL, L, or m3)
density - mass per unit volume (g/mL)
temperature - measure of avg. kinetic energy - Kelvin, Fahrenheit, or Celsius (K, °F or °C)
time - duration of evets - second (s)
Identify the proper unit for matter and the way in which it changes
Proper Unit: mole (mol)
Ways Matter Changes:
- Physical change – alters form/appearance
- Chemical change – produces new substances
Identify the three basic parts of a measurement
Units, Significant figures, magnitude (the overall value)
Accuracy vs. Precision
Steps for Writing a Conclusion
Restate Hypothesis/Objective – Briefly restate what the experiment was testing or aiming to find.
Summary of Results – Give the main results and state if they supported or refuted the hypothesis. (specific evidience)
Analysis/Interpretation – Explain patterns or trends in the data, often with an R² value:
0.90–1.00 = strong correlation
0.70–0.89 = reasonable correlation
0.60–0.69 = weak correlation
0.59 or lower = no correlation
Limitations – Note errors or weaknesses in the experiment, including percent error if applicable.
Further Research – Suggest next steps, new experiments, or ways to improve the design.
Isotopes
Atoms of the same element that have different numbers of neutrons (and therefore, masses)
Ex:
C-12, C-13, C-14
Common isotope - mass of isotope is the same as the rounded atomic mass on the periodic table
Uncommon isotope - mass of isotope is different than the rounded atomic mass on the periodic table
Cations + Anions
Cations:
Typically metals
result of when electrons are lost
Anions:
Typically non-mentals
result of when electrons are gained by atom
Groups & Periods
Groups/Families - Columns (vertical)
Elements in the same group have similar chemical properties and the same number of valence electrons, and therefore ionic charge.
Periods - Rows (horizontal)
Elements in the same period have the same number of energy levels in their atoms.
Role of Nucleus
The positive protons in the nucleus attract the negative electrons, keeping the electrons in the atom!
Opposite charges attract!
Shorter distance between particles = stronger attraction
Therefore, core electrons have a stronger attraction to the nucleus!
Electronegativity
an atom’s ability to attract another atom’s electrons
Polar vs. Nonpolar covalent bonds
Polar: Atoms share electrons unevenly
Non-polar: Atoms share electrons evenly
Hydrates
salts that attract and absorb water
The molar mass of a hydrate includes water.
MF + EF
The empirical formula gives the lowest whole number ratio of the atoms in a compound.
Ex.: AlN3 or CO2
The molecular formula tells the actual number of each kind of atom present in a molecule.
Ex.: H2O2
Instruments
acid spill on lab bench - notify teacher and use neutralizing powder
to mix two chemicals - use stir bar
group names on PT
1 - Alkali Metals
1 - Alkaline Earth metals
2nd last - hallogens
last - noble gases
