Ch 1 - What is Chemistry? Flashcards
Science
The experimental investigation and explanation of natural phenomena; knowledge from experience
How are science and technology changing?
Change is accelerating: 100 years from now will be more different from today than today is from 500 years ago.
Technology
The application of scientific knowledge; the use of knowledge in practical applications
Is science always right?
No, it is a human endeavor
Is technology always good?
No, it is driven by human desires (the atomic bomb, etc)
Chemistry
The study of matter and the transformation(s) it undergoes; “central science”; a bridge between physics and biology
Matter
Anything that has mass and occupies space; “stuff”
Transformation
Changes in matter
Pure substance
Only a single type of matter (table salt, table sugar/sucrose)
Mixture
2+ substances intermixed (mixture of salt and sugar, rocks); can be separated by physical means
Elemental substance
A pure substance made of only one type of atom (pure gold Au, oxygen in the air O2)
Compound
A pure substance made of 2+ different elements in a fixed ratio (H2O)
Homogeneous mixture
A mixture with a uniform composition (brass, sugar dissolved in water)
Heterogeneous mixture
A mixture without a uniform composition (oil and water, sugar and salt mixed together)
Element
The basic building block of all matter; periodic table of elements; ~119 known (90 natural, 23 synthetic)
Who first proposed the atomic theory?
Democritus in ~400 BC theorized the smaller unit if all matter was called an atom
Who disagreed with the atomic theory?
Aristotle ~400 BC proposed a continuous model suggesting that there was no limit to how small something could go. This theory won out for over 2000 years.
Atoms
The smallest complete unit if am element
Chemical formula
The number if each type of atom that makes up the smallest unit of the compound
Physical transformation
The same substance, but a different state of matter
States of matter
Solid, liquid, gas
Characteristics of a solid
Has a definite shape and volume
Characteristics of a liquid
Has a definite volume, but no definite shape
Characteristics of a gas
Has neither definite volume or definite shape
Physical properties
Those properties of a substance that can be observed without changing the substance.
Examples of physical properties
Color. Mass. Weight. Scent. Hardness. Boiling point. Melting point. Density.
Physical change
A change in which the chemical identity if the substance is not changed. (Melting, freezing, reshaping)
Freezing
A substance changing from a liquid state of matter to a solid state of matter
Melting
A substance changing from a solid state of matter to a liquid state of matter
Vaporization
A substance changing from a liquid state of matter to a gaseous state of matter
Condensation
A substance changing from a gaseous state of matter to a liquid state of matter
Sublimation
A substance changing from a solid state of matter directly to a gaseous state of matter
Chemical properties
Those properties of a substance that can only be studied by forming new substances; describes how a substance reacts
Examples if chemical properties/changes
Rusting. Burning. Tarnishing. Exploding. Toxicity. Inert (does not react with anything).
Chemical changes
Changes in being the chemical identity of a substance is changed; when a substance changes to a different substance(s); described when substances undergo a chemical change.
Chemical reaction
Describes a chemical transformation
Reactants
The starting substances in a chemical reaction
Products
The newly formed substances following a chemical reaction
5 characteristics of science
1) Testable
2) Reproducible
3) Explanatory
4) Predictive
5) Tentative
Scientific method
1) Experiment
2) Law
3) Theory
4) Model
Observation –> Hypothesis –> Experiments –> Theory
Experiment
Observations and data
Law
Concise summary of outcome(s)
Theory
Attempt to explain why a law exists; a set of tested hypotheses that explain natural phenomena; best current explanation; always tentative and may change as observations continue/change
Model
A physical picture or mathematical expression of a theory; tangible items/pictures used to represent invisible processes; helps to apply, understand, and visualize a theories; always incomplete and simplified –> limited
Scientific hypothesis
Testable explanations of observed data; tested by designing and performing experiments
Relationship between a theory and a law
A theory attempts to explain why a least is correct
Relationship between a law and experimental data
A law is a summary of experimental results
Limitations to the scientific method
1) Sample size
2) Shows avg behavior of the group
3) Bias
4) Science is limited to studying that which is observable as well as processes in which variables can be controlled
Bias
Stein preference or inclination that inhibits impartial judgement
Molecule
A group of 2+ atoms held together by chemical bonds
Molecular model
3D representations of molecules (a diamond)
