Physical science jones Chapter 2: Matter Physical science jones

Good Morning! Please find a partner and a book to share. Get out one sheet of paper and something to write with. Open to page 38.

Get To Know Your Vocab! On a sheet of paper, draw 6 of these: Characteristics Definition Vocabulary Word Non-examples Examples

Get To Know Your Vocab! For each of the diagrams, write the vocab word and its definition. We will discuss characteristics, examples, and non-examples. Atom Molecule Element Compound Pure Substance Mixture

Atom Characteristics: Examples: Non-examples: All atoms of an element are identical in properties Atoms are composed of protons, neutrons, and electrons Atoms of different elements can combine to make compounds Atoms cannot be broken down any further Examples: An atom of hydrogen An atom of oxygen An atom gold Non-examples: A molecule of water A molecule of air A molecule of salt

Molecule Characteristics Examples: Non-examples: All molecules of a compound are identical in properties Molecules are composed of atoms of 2 or more elements Molecules can be broken down into individual atoms of elements Examples: A molecule of sugar A molecule of carbon dioxide A molecule of water Non-examples: An atom of sodium An atom of silver An atom of helium

Element Characteristics: Examples: Non-examples: All elements can be found on the periodic table Each element is composed of identical atoms Elements can combine to produce compounds Each element is classified as a metal, nonmetal, or metalloid Examples: Sodium Potassium Chlorine Non-examples: Water Salt Air

Compound Characteristics: Examples: Non-examples All compounds are composed of 2 or more elements Compounds consist of identical molecules Compounds can have different properties than the elements they are made of Examples: Salt (sodium chloride) Water (H2O) Glucose Non-examples Carbon Steel Italian dressing

Pure Substance Characteristics: Examples: Non-examples: The composition of pure substances will never change The properties of pure substances will never change Pure substances can be mixed to produce mixtures Pure substances cannot be separated physically Examples: Any element Any compound Non-examples: Salt water Sweet tea Steel Italian dressing

Mixture Characteristics: Examples: Non-examples: Mixtures have various amounts of their components Mixtures are produced by mixing pure substances together Mixtures can be separated physically Examples: Grape juice Air Chicken noodle soup Non-examples: Any element Any compound

What is matter? Matter: Anything that has mass and takes up space Examples: your desk, air Non-examples: sound, light All matter is composed of atoms and molecules

Element Symbols and Chemical Formulas Represent elements Are found on the periodic table ONE capital letter, and sometimes one lowercase letter Na O Fe Chemical formulas Represent compounds Two or more element symbols put together AT LEAST TWO capital letters, and sometimes small numbers called subscripts H2O NaCl C6H12O6

Chemical Formulas The subscripts represent how many atoms of that element are in the compound How many atoms of each element are there in C6H12O6?

Chemical Formulas The subscripts represent how many atoms of that element are in the compound How many atoms of each element are there in C6H12O6? 6 Carbon atoms 12 Hydrogen atoms 6 Oxygen atoms

Chemical Formulas How many atoms of each element are in (NH4)2SO4?

Chemical Formulas How many atoms of each element are in (NH4)2SO4? 2 Nitrogen atoms 8 Hydrogen atoms 1 Sulfur atom 4 Oxygen atoms

Mixtures Can be divided into two groups: Heterogeneous – substances aren’t evenly mixed Flour + water mix to form a cloudy white mixture Oil + water may mix temporarily but will eventually settle out Homogeneous – components of the mixture are evenly distributed Gasoline Sugar-water mixture

Mixtures Can you think of any examples where a gas is mixed in a liquid?

Mixtures Can you think of any examples where a gas is mixed in a liquid? Soda Gas is not dissolved in the liquid, but is mixed in As the gas bubbles rise to the surface of the soda, they can escape into the atomsphere Once all the bubbles from the mixture have escaped, you have flat soda! Meringue (for use in pie) Egg whites are whipped with enough air to produce foam The foam is baked in the oven to solidify, to produce meringue

Properties of Elements and Compounds Properties that describe a certain substance are either physical or chemical Physical properties are characteristics that describe the appearance of that substance Color Shape Melting point/boiling point Chemical properties are characteristics that relate a substance’s ability to undergo changes that transform it into different substances Ability to burn Ability to rot or decompose

Physical Properties Describe matter Shape Color Odor Texture State of matter (solid, liquid, or gas)

Physical Properties Can be constant for certain substances Melting point Boiling point Freezing point Density How much matter is contained in a certain volume of substance Density = mass/volume Unit: g/cm3 or g/mL Unit for mass: grams, Unit for volume: cm3 or mL

Chemical Properties Describe how a substance reacts Reactivity Ability to react with oxygen, acid, water, etc. Flammability Ability to burn Other examples Ability to rot Ability to rust

Changes in Elements and Compounds A change in a substance can either be described as physical or chemical. A physical change does not change the composition of that substance. Melting/boiling Change of state (solid  liquid  gas) Breaking/tearing A chemical change occurs when one or more substances are converted into different substances Burning Rusting Rotting

Physical Changes Do not change a substance’s identity Examples: Dissolving Cutting Sanding Crushing Breaking Tearing Changing state of matter (solid  liquid  gas)

Chemical Changes Occurs when one or more substance changes into entirely new substances with different properties Examples: Baking a cake! Iron rusting Milk souring Signs of a chemical change: Color change Production of gas Production of precipitate Production of energy in the form of heat or light

Separating Mixtures Mixtures can be separated physically Straining Centrifugation Distillation

When are reactions reversible? Some physical changes are reversible, some are not Dissolving a substance, then using distillation techniques to separate the components Some chemical changes are reversible, some are not You cannot “unbake” a cake When water is formed, it can be split back into oxygen and hydrogen A double arrow represents a reversible reaction A + B  C + D