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Chemistry Study Guide #1



9/16/03

Chemistry Review

Part I: Book Review

Chemical- Any substance with a definite composition

Physical states

Solid- Fixed volume and shape

Liquid- Fixed volume and variable shape

Gas- Variable volume and gas

Decomposition- One reactant breaks into two products

Activation energy- needed to start reaction (not always needed)

Exothermic reaction (hot)- releases energy

Endothermic reaction (cold)- absorbs energy

Matter- anything that has mass or volume

Mass- quantity of the matter in an object

Weight- the force produced by gravity acting on mass

Newtons- the unit of force

Qualitative terms- descriptive terms- light, heavy, large, etc.

Quantitative terms- numbers and units

SI units- K h dK d c m

Derived units- combining several base units ex.- D= m/v

Physical property- can be measured without changing chemical nature

Physical changes- can occour without changing chemical nature

Chemical change- substances turning into new substances

Evidence of a chemical change:

Evolution of a gas

Formation of a precipitate

Evolution or absorption of heat

Emission of light

Color change

Nature of matter:

111 different elements

90% atoms are hydrogen

70% mass Earth’s crust is oxygen and silicon

Life: carbon, hydrogen, oxygen, nitrogen

Allotrope- different molecular forms ex. 02 and 03

Classification

Compound- pure substance with atoms from two or more different elements

Covalent compounds- neutral

Ionic compounds- have electrical charge

Acid Base

Sour Bitter

PH less than 7 pH greater than 7

React with bases and metals to form salts React with acids to form salts

Organic compounds have carbon

Formulas

Molecular formula ex. C9H8O4

Structural formula

Ball and stick model

Space-fill model

Mixture- Two or more pure substances mixed together

Homogeneous mixture- Uniform distribution

Heterogeneous mixture- Uneven distribution

Mixtures vs. Compouns

1. Mixtures are like substances it contains, but compounds often don’t resemble contents

2. Compounds have definite composition by mass. Mixtures can vary in proportion

Purity (Best-Worst)

1. Primary- standard-grade

2. Reagent- grade

3. Commercial/tech grade

Chemical energy- matter possesses it because of chemical makeup

Chemical bond- force of attraction

Kinetic energy- due to motion

Potential energy- position to other objects

Energy- capacity to do work

Law of conservation of energy- energy can be neither created not destroyed

Heat- total of kinetic energy

System- all components being studied

Temperature- average kinetic energy of random motion of particles in a substance

Zero degrees Kelvin = 273.15 degrees Celcius

Specific heat capacity- amount of energy needed to raise the temperature of 1g of substance by 1k. Expressed in (J/gK)

SI unit of energy- Joule, J

E= mc squared- Law by Albert Einstein 1905. Says energy = mass x (speed of light in a vacuum) squared

1 Joule is 1Kg m2/s2

Polymer- long chain

Hypothesis- reasonable, testable explanation

Theory- broad, generalization based on observation, experimentation and reasoning

Scientific law- statement/mathematic expression that are consistently true

Law of Conservation of Mass- Product mass= reactant mass

Accuracy- how close to true value

Precision- how close several measures of some quantity agree

Part II: Notes

Quantitative research- Controlled experiments that result in numbers

Data collection- tables

Descriptive research- Observational data. No number values- just senses (smell, color, etc.)

Scientific Method- A systematic approach to problem solving. There is no ONE scientific method

Hypothesis- educated guess

Theory- Most logical explanation after testing

Law- A generally accepted theory (many trials)

Dependant variable- condition that is observed (results)

Density measures the mass in a given volume of a substance. Density is the ratio of two measured properties of matter; mass and volume. D= m/v

Density is a derived unit (need to calculate with two other units)

The density of a pure substance is a constant. Density can help you identify unknown substances

Water has a density of .99820 g/cm3 at 20degrees Celcius (most give water a density of one)

Accuracy- how close the measurement is to the actual value

Accuracy can be true of an individual measurement or the average of several

Precision- how well the measurement can be repeated Precision requires several measurements before anything can be deduced

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