Building Blocks of Matter

Building Blocks of Matter

1. Matter is anything that has mass and takes up space

1. Physical properties of matter are those that can be determined without changing the matter
2. Chemical properties of matter can only be determined by changing the matter

1. An atom is the smallest part of an element that still has the properties of that element

1. All atoms have a neutral charge and are in constant motion
2. An atom consists of a central nucleus and electrons
3. In the nucleus are two main sub-atomic particles called protons and neutrons

1. the nucleus contains the vast majority of the mass of an atom
2. protons are positively charged and have a mass of 1 amu (atomic mass unit)
3. neutrons have no charge and also have a mass of 1 amu
4. it is the number of protons in the nucleus that determine what element it is

1. Electrons orbit the nucleus and have a negative charge

1. electrons are found in an electron cloud – a region around the nucleus
2. electrons are minute – 1836 together = 1amu

1. An element is a pure substance made up of only one type of atom

1. Some of the atoms of an element may have a different number of neutrons – this is called an isotope of the element
2. Hydrogen is an example of this phenomenon

1. H with no neutrons is called protium
2. H with one neutron is called deuterium
3. H with two neutrons is called tritium

1. All elements are organized on the Periodic Table of the Elements

1. Dmitri Mendeleev developed the first Periodic Table of the Elements

1. the elements were arranged by their atomic mass (the # of protons and neutrons in the nucleus)

1. Henry Moseley discovered what is now called the atomic number – the number of protons in the nucleus

1. when Moseley arranged all the elements by using increasing atomic numbers, patterns became apparent
2. elements with similar properties would always fall into the same columns

1) there are 18 such columns called groups or families

1. each element is represented by a one or two letter symbol – He for Helium, etc.

1. The majority of elements are shiny solids that conduct electricity – they’re called metals
2. A smaller number of elements are poor conductors and lack the luster of metals – they’re called the non-metals
3. A smaller group – all gases at room temperature – seldom react with other elements and are called the noble gases
4. Each row of the Periodic Table of the Elements represents a period

1. elements to the far left are the most reactive metals
2. as you move to the right the elements become less and less metallic and more and more non-metallic
3. elements on the far right are non-metals
4. metalloids are elements with both metallic and non-metallic properties

1) they are located on either side of the zigzag line on the Periodic Table of the Elements

1. the reactivity of the non-metals increases to the right until you reach the noble gases

1. Molecules and Compounds

1. A molecule is composed of more than one atom combined

1. O2 is a molecule and so is H20

1. A compound is composed of two or more elements chemically combined

1. a chemical formula is used to represent a compound
2. a subscript tells the numbers of each atom in a compound
3. no subscript means there is one atom

1. Mixtures – when substances combine but keep their individual properties

1. The substance can be separated by physical means

1. a magnet separates a mixture of magnetic and non-magnetic matter
2. filtration separates a liquid and solid or two solids with different particle sizes
3. evaporation separates substances in a solution

1) after the solvent evaporates the solute is left behind

1. distillation separates two liquids by differences in their boiling points
2. a centrifuge separates materials of different densities (in solution) by spinning around a central axis

1. Physical and Chemical Changes

1. Physical Change – the chemical properties of the matter are not changed

1. forming a mixture involves a physical change
2. melting snow is an example of a physical change
3. phase changes are another good example of physical change

1. Chemical Change – the chemical and physical properties of the matter are changed

1. the matter created has a new chemical composition and different properties then the matter from which it was formed
2. forming a compound involves a chemical change – Na+Cl = Table Salt

1. A chemical equation summarizes a chemical reaction

1. the chemicals that begin the reaction are called reactants
2. the substances produced by the chemical reaction are called the products
3. an arrow stands for “yields”

1. The forces that hold atoms together are called chemical bonds – there are several types

1. Ionic Bonding – a bond formed when atoms gain or lose electrons

1. an ion is an electrically charged particle – more protons than electrons = positively charged while more electrons than protons = negatively charged
2. ions of opposite electrical charge combine in ionic bonding
3. NaCl is an example
4. A metal and a non-metal bond most often

1. Covalent Bonding – a bond formed when atoms share electrons

1. some atoms have incomplete outer electron levels
2. filling the outer level by sharing electrons from other atoms is covalent bonding
3. H2O is an example
4. two non-metals form covalent bonds most often

1. Metallic Bonding – electrons are shared with many nuclei and are free to migrate around the metallic material

1. the electrons are not bound to any one nuclei like covalent bonding
2. this bonding happens in pure metals, only

1. Phases of Matter – 4 phases (forms) of matter exist

1. The phase of matter is related to how close together the particles are to one another and their relative motion

a. generally, the higher the temperature, the higher the rate of molecular motion

1. Solids have a definite shape and volume

1. the particles in a solid are moving the slowest and are closest together

1. Liquids have a definite volume but take on the shape of their container

1. the movement of particles in a liquid is faster than in a solid but slower than in a gas
2. the particles are farther apart than in a solid

1. Gases have no definite shape or volume

1. the particles are moving faster than those of a solid or liquid
2. the particles are more widely spaced than those of a solid or liquid

1. Plasma – particles that have been stripped of their electrons

1. particles are moving very fast
2. temperatures of 1,000,000C are required to form plasmas
3. stars (like the Sun) contain plasma – there is none on planet Earth

1. Solution – a uniform (the same throughout) mixture of two or more substances

1. This mixture could be a mixture of solids, liquids, gases, or any combination of these

1. air is a solution of gases (gases in other gases)
2. bubbles in soda are a solution of gases in liquids
3. alloys (bronze, a mixture of copper and tin) are a solution of solids in other solids

1. Solubility – how well a type of matter can dissolve into a solvent

1. The substance being dissolved in called the solute
2. The substance the solute is being dissolved into is called the solvent
3. The “universal solvent” is water – many substances dissolve into water
4. The temperature of the solvent affects solubility – the higher the temperature of the solvent the greater the amount of solute it can dissolve
5. The higher the temperature of the solvent the faster the solute dissolves
6. Pressure has an effect on solubility when a gas is dissolved into a liquid – the higher the pressure, the more gas can be dissolved into the liquid
7. The surface area of the solute affects solubility – the greater the surface area, the faster the solute will dissolve

1. surface area – how much “outside” can come into contact with the environment

1. Having the solvent stirred helps the solute dissolve
2. A solution appears the same throughout – it’s uniform in composition

1. Solubility Graphs – a graph to summarize the solubility of various substances in a given mass of water at changing temperatures

1. The X-axis gives the temperature
2. The Y-axis tells the grams of solute that can be dissolved into 100 grams of water
3. The curves on the graph show the number of grams needed to create a saturated solution in 100 grams of water at a particular temperature
4. Three types of solutions exist

1. unsaturated solution – one that can hold more solute for a given temperature

1) points below the line indicate an unsaturated condition

1. saturated solution – one that holds the maximum amount of solute it can for a given temperature

1) points directly on the line indicate a saturated condition

1. supersaturated solution – one that is holding more solute than it normally can for a given temperature

1) to create a supersaturated solution you first heat up the solvent – hot solvents hold more solute than cooler ones – add more solute

2) cool down the solvent – the solvent can now hold less than before

3) what comes out of solution (the excess solute) is said to have crystallized

4) points above the line indicate a supersaturated condition

1. Chemical Reactions

1. Some types of matter are more reactive than others

1. hydrogen is a very reactive gas
2. sodium and potassium are very reactive metals
3. fluorine and chlorine are very reactive non-metals
4. when a metal and a non-metal react together (ionic bonding) it produces a salt
5. noble gases are highly stable (inert) and don’t react much at all

1. During a chemical reaction the mass of the reactants must equal the mass of the products

1. matter cannot be created or destroyed , only rearranged
2. this is called the Law of Conservation of Mass

1. Rates of Reactions

1. Collision Theory – all atoms and molecules are in constant motion – it they collide with sufficient force, a chemical reaction may occur

1. increasing the temperature of the reactants makes them move faster, collide more often and more violently, so chemical reactions speed up
2. increasing the concentration of the reactants makes collisions more likely so chemical reactions speed up
3. in the human body, chemical reactions take place when substance dissolve in water

1) when substances dissolve, ions may be produced

2) ions are more reactive than atoms so dissolving things speeds up chemical reactions

1. the dissolving capacity of water makes chemical reactions easier to take place in the non-living environment, too

1. Acids and Bases

1. Acids – a large class of sour tasting substances capable of turning blue litmus paper red

1. acids react with and dissolve certain metals to form salts
2. acids react with bases to form salts
3. an acid can be though of as a hydrogen ion donor (H+)

1. Base – a large class of bitter tasting compounds capable of turning red litmus paper blue

1. bases react with acids to form salts
2. a base can be thought of as a hydroxyl ion donor (OH_)

1. pH Scale – a scale used to measure the strength of an acid or base

1. the scale goes from 0 to 14
2. distilled water (pH 7.0) is neutral (neither acid nor base)
3. less than 7.0 is acidic, greater than 7.0 is basic
4. the lower the pH number, the stronger the acid
5. the higher the pH number, the stronger the base

1. Acid Precipitation/Acid Rain

1. Acid precipitation comes mostly from the burning of coal rich in sulfur compounds by powerplants in the Midwest

1. when the coal is burned, sulfur oxides form
2. these sulfur oxides combine with water droplets in the air to form sulfuric acid
3. the jet streams bring this acid precipitation to New York State

1. Limestone or Marble bedrock can neutralize the acid
2. Where these two types of bedrock don’t occur, life in lakes can be destroyed

1. some lakes have a pH value the same as lemon juice (very acid)
2. over 200 lakes in the Adirondacks have been poisoned by acid precipitation

1. Acid precipitation affects soils, crops, and forests, too

1. the Black Forest of Bavaria, Germany has been destroyed by acid rain

1. Laws have been passed to limit the amount of sulfur compounds released into the air

1. switching to low sulfur coal or other low sulfur fuels would help
2. using alternate energy sources would help
3. using less energy overall would help, too

1. Global Warming

1. Burning fossil fuels releases greenhouse gases into the atmosphere

1. carbon dioxide, water vapor, nitrogen oxides, CFC’s, and methane are greenhouse gases

1. These gases let visible light enter our atmosphere but prevent infrared rays (heat) from leaving the atmosphere

1. this causes our atmosphere to heat up

1. A warmer atmosphere could lead to:

1. coastal flooding as the ice caps melt
2. climate changes
3. shifts in agricultural patterns
4. change in present day ecosystems
5. spread of tropical diseases into mid-latitude locales

1. Ozone Depletion

1. Ozone is a gas in a portion of our upper atmosphere called the stratosphere
2. It’s very important because it blocks dangerous ultraviolet rays from the Sun – they are absorbed before they reach the surface where we live

1. ultraviolet rays can cause skin cancer to those exposed to them
2. the UV rays damage crops
3. the UV rays are also believed to damage simple animal life forms that live on land and in the oceans

1. Recent satellite data shows that the amount of ozone in our atmosphere has decreased, especially in the vicinity of the Poles

1. more UV rays can enter through these “holes” in the ozone layer
2. over time, the “holes” seem to change size and location

1. The use of a class of chemicals called chlorofluorocarbons (CFC’s) is the major cause of ozone depletion

1. CFC’s are a refrigerant
2. they are used as a propellant in spray cans
3. they are also used to manufacture styrofoam

1. CFC’s chemically react with ozone molecules and break them down into simpler components
2. They have been banned in the United States and Canada but not in other parts of the world
3. What can be done to limit the damage?

1. find replacements
2. dispose of refrigerators and air conditioners properly
3. continue to pressure other countries to do the same