Chem - Finals Study Guide

Formula for density

D = M/V (Density = Mass/Volume)

What determines how accurate and precise your data is?

Accuracy reflects how close a measurement is to a known or accepted value, while precision reflects how reproducible measurements are, even if they are far from the accepted value. Measurements that are both precise and accurate are repeatable and very close to true values.

Percent Error

\[(average of measured value) - (accepted value) / (accepted value)] * 100

Erroneous data can be caused by...

Random errors: statistical fluctuations due to the precision limitations of equipment (ex. instrument resolution, parallax)

Systematic errors

reproducible inaccuracies that are difficult to detect statistically (ex. instrument drift, lag time)

Personal Error

These errors come from carelessness, poor technique, or bias on the part of the experimenter.

Anomolous Data

Data that does not fit with the rest of a data set. This kind of data can never be thrown out because they may suggest an interesting phenomenon that could lead to a new discovery, or they may simply be the result of a mistake or random fluctuations.

What are the important characteristics of an accurate graph?

Title: (independent variable) over (dependent variable)

Labels on axis: (x-independent, y-dependent)

Scaling: correct intervals on axis

Key: indicate every mark made

Break: consistent skip of numbers

Signs of physical reaction

Change in size, shape, texture or state

Signs of a chemical reaction

change in temperature, formation of bubbles, precipitate forms, color change, change in smell, difficult to/cannot reverse

Examples of physical reaction

melting, freezing, boiling, shredding, dissolving, cutting, bending, anything that can be reversed

Examples of chemical reaction

burning, cooking, rusting, rotting, baking, digestion, curdling, anything that cannot be reversed

Solid

A state of matter that has a definite shape and a definite volume

Liquid

A state of matter that has no definite shape but has a definite volume

Gas

A state of matter with no definite shape or volume

Phase Changes

transitions from one state to another (melting, freezing, vaporization, condensation, sublimation, deposition)

How do you find the number of protons in an atom?

The number of protons in an atom is equal to the atomic number of the element.

How do you find the number of neutrons in an atom?

The number of neutrons is equal to the difference between the mass number of the atom and the atomic number.

How do you find the number of electrons in an atom?

The number of electrons in a neutral atom is equal to the number of protons.

What is the difference between the total number of electrons and valence electrons?

Atomic number is the total number of electrons. The valence electrons are only those in the outer shell.

Atomic number

the number of protons in the nucleus of an atom

Atomic weight

Average of the mass numbers of all isotopes

Oxidation number

Positive or negative number that indicates how many electrons an atom has gained, lost, or shared to become stable

Calorimetry equation

q=mcΔT where C = 1cal/g℃ (Q = heat transferred, m = mass of solution, c = specific heat capacity, ΔT = temperature change) Find Q if given a mass, initial Temp and final Temp. This equation can be found in The Laws of Thermodynamics.

What is the difference between Energy and Temperature?

Temperature is an intensive quantity that does not depend on the mass of material that you have. Energy is an extensive quantity that does depend on the amount of matter involved.

Physical properties of ionic compounds

Ionic compounds are solids and are hard to break due to the strong force of attraction between the positive and negative ions. However, they break into pieces when pressure is applied. So they are considered brittle.

Chemical properties of ionic compounds

A large amount of energy is required to break the ionic bonds between the atoms so they have high melting and boiling points.

Physical properties of covalent compounds

can exist as all types of matter at room temp

low boiling/melting point

often water insoluble

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