Chem Unit Test 1

Chemistry

Chemistry

Study of composition, structure, and properties of matter and changes matter undergoes

Chemistry 6 branches

• Organic Chemistry

• Biochemistry

• Inorganic Chemistry

• Physical Chemistry

• Analytical Chemistry

• Theoretical Chemistry

Organic Chemistry

study of compounds that contain carbon

Biochemistry

study of substances and processes occurring in living things

Inorganic Chemistry

study of non-organic substances

Physical Chemistry

study of properties and changes of matter and how they relate to energy

Analytical Chemistry

identification of components and composition of materials

Theoretical Chemistry

use of math and computers to understand chemical behavior

Chemicals

any substance that has definite composition

Research

basic, applied, technological research

Basic Research

research carried out for sake of increasing knowledge

applied research

carried out to solve a problem

technological research

involves the use of technology to improve our quality of life

Ex. computers, biodegradable materials

scientific method

logical, systematic approach to solution of a scientific problem

Qualitative

use senses

Quantitative

make a measurement

1 Step

Make observation (Qualitative/Quantitative)

2 Step

Leads to Question

3 Step

Hypothesis= proposed explanation for an observation

4 step

preform an experiment

-tests 1 variable

Manipulated/Independent Variable

variable that will be manipulated

Observed/Dependent variable

variable will change depending on independent variable

5 step

Analyze Results

• prove hypothesis and develop theory

• disprove hypothesis then return to step 3

Theory

well-tested explanation for a broad set of observations

• CAN NEVER BE PROVED —> ROOM FOR CHANGE

Law

statement summarizes many observations or experiments

Matter

anything that has mass and takes up space

Mixtures

a blend of two or more kinds of matter, each keeps own identity and properties (NO DEFINITE OR CONSTANT COMPOSITION)

Ex. sugar water, blood, air

Pure Substance

every sample of the substance has the same composition and characteristics

(compounds + elements)

Ex. Gold, Vinegar

Homogenous Mixture/ Solutions

Uniform throughout

Ex. sugar water, air

Heterogenous mixture

not uniform throughout (CAN BE SEPARATED BY PHYSICAL MEANS)

Ex. blood, wood

Compounds

two or more elements that are chemically bonded

Ex. water, sucrose

Elements

Made of only one kind of atom

Ex. gold, carbon

mass

measured in grams

volume

space- measured in liters

element

-contains one kind of atom

Ex. He, Li, Be, B, C

diatomic

more than one atom (STILL ONE ELEMENT)

Ex. H2, N2, O2

compound

-Pure substance that contains two or more elements

• Can become broken down to simpler substances (elements)

• REPRESENTED BY CHEMICAL FORMULAS

  Ex. Water (H2O), Table Salt (NaCl)

Atoms +Molecules

-building blocks of matter (make up elements + compounds)

Atom

smallest unit of an element that maintains its chemical identity

Physical property

a change in a substance’s appearance, does not change its chemical make-up

Chemical Property

a change in a substance that transforms it into a new substance

Intensive Property

property that does not change when you change its amount

Ex. Temp, color, texture, melting point, boiling point

Extensive Property

a property that changes when size of sample changes

Ex. Mass, volume, length

Physical Change

a change in a substance’s physical appearance but not chemically

• Change Size and Shape

• stretch, compress, shatter, tear, break

Ductile

a substance that can be drawn into wires

malleable

a substance that can made into a thin sheet

Dissolving

a physical change

Ex. a substance like sugar dissolves and gets broken apart by the water into individual molecules that are too small to see, but still just a change in size and shape

Changing Temperature

-when temperature changes enough, substances will experience a change in phase because heating matter causes —→ expansion

cooling cause —→ contraction

DOES NOT CHANGE SUBSTANCE IDENTITY

melted

solids ——> liquids

frozen

liquids —→ solids

boiled or evaporated

liquids ——> gases

condensed

gases —→ liquids

sublimed

solids ——> gases

chemical property

chemical change in which one or more substance converted to different substances

chemical change

chemical change

substances are placed together and they exchange or share electrons

Chemical change signs

1. Color

2. precipitate forms

3. bubbles

4. light and/or heat given off

5. new substance formed

precipitate

turbid solid formed when two solutions are placed together

Chemical exchange examples

1. Burning/ Combustion

2. Acid Rain Damage

3. Food Spoilage

4. Rusting/ Corrosion

5. Photosynthesis

Matter classification

solid, liquid, gas, pure substance, mixtures

Density

mass per unit of volume (TIGHTLY PACKED OR HEAVINESS OF MOLECULES)

Formula: m/d

Gases + Density

greater kinetic energy in molecules → greater the volume→ less dense gas is

Liquids

more dissolved solids in a solution → more dense

Ex. cold water in lakes sink (mixing of water, nutrients, other substances) →kinetic energy

solids

ice less dense than water

Ex. lakes and ponds have thin layer of ice covering in winter, with water under

Ex. various rocks, woods, metals have specific density to substance

determining density

regular shapes- mass

Ex. cubes, cylinders, spheres, cones

• use graduated cylinder

• adding water to predetermined level

• gently drop in irregularly shaped object

• read graduated cylinder - record

• subtract first water level from second= volume

density factors

1. size

2. mass

3. arrangement of atoms