Properties of MAtter

Objectives Identify properties of amtter as extensive or intensive Define physical property and list several common physical properties of substances Differentiate among three states of matter Describe a physical change

Key Concepts How can properties used to describe matter be classified?* Why do all samples of substance have the same intensive properties?* What are three states of matter?* How can physical changes be classified?*

Describing MAtter Properties used to describe matter can be classified as extensive or intensive*

Describing MAtter 2 properties used to describe matter: Extensive property Intensive property

Extensive property Depends on the amount of matter in a sample Common extensive properties: Mass – measure of the amount of matter the object contains (grams) Volume – measure of space occupied by the object Length Particle number Electrical charge Don’t confuse mass with weight (a measure of gravity)

Intensive property Depends on the type of matter in a sample Common intensive properties: Density – mass per unit volume Melting point and boiling point – temp at which substance melts or boils Magnetization

Identifying substance Substance – matter that has a uniform and definite composition Every sample of a given substance has identical properties because each sample is the same

Properties Words that describe matter 2 types of identifying properties: Physical property Chemical property

Physical property Property that can be observed and measured without changing the material’s composition Examples: Color Hardness Melting point Boiling point

Chemical property Property that can only be observed by changing the composition of the material Examples: Ability to burn Decomposition Fermentation Fermentation – metabolic process converting sugar to acid

Recap Properties describing matter Extensive Intensive Properties identifying matter Physical Chemical

States of matter*

Solid Definite shape and volume Does not flow Does not take shape of container Increase in temperature = small expansion Does not compress Compressibility = measure of volume change resulting from pressure

Liquid Definite volume Take the shape of container Flows Increase in temperature = small expansion Does not compress

Gas No definite volume No definite shape – will take shape of container Flows Increase in temperature results in large expansion Can be compressed

Gas (Vapor) Substance that is currently a gas but normally is a liquid or solid at room temperature Occurs with an increase in temperature “Water vapor”

Plasma 4th state of matter Formed at high temperatures Ionized phase of matter as found in the sun

Examples of each

Copper phases - solid

Copper phases - liquid

Copper phase – vapor (Gas)

Physical vs. chemical change Physical change – changes the visible appearance, without changing the composition of the material Boil, melt, cut, bend, split Is boiled water still water? Can be reversible or irreversible*

Physical vs. chemical change Chemical change – change where a new form of matter is formed Rust, burn, decompose Irreversible

Assessment In what way are liquids and gases alike? In what way are liquids and solids different? Why do all samples of a given substance have the same intensive properties?

Mixtures

objectives Categorize a sample of matter as a substance or a mixture Distinguish between homogeneous and heterogeneous samples of matter Describe two ways that components of mixtures can be separated

Key Concepts How can mixtures be classified?* How can mixtures be separated?*

mixtures Mixture – made of 2 or more different components Classified as either:* Heterogeneous mixture Homogeneous mixture

Heterogeneous mixture Mixture is not uniform in composition Examples: Chocolate chip cookie Soil

Homogeneous mixture Mixture with same composition throughout AKA “solution” Examples: Kool-aid Salt water

Solutions Mixed molecule by molecule thus too small to see different parts but no definite composition Can occur between any state of matter Gas in gas Gas in liquid Solid in liquid

phase Any part of a sample with uniform composition of properties How many phases in a homogeneous mixture? How many phases in a heterogeneous mixture?

Separating mixtures Some mixtures can be separated easily by physical means Can you name some? Differences in physical properties can be used to separate mixtures*

filtration Separates a solid from the liquid in a heterogeneous mixture

Paper chromatography Separate components of dyes such as ink

distillation Takes advantage of different boiling points Liquid is boiled to produce vapor that is then condensed to liquid Separate homogeneous mixtures

assessment Classify each of the following as homogeneous or heterogeneous: Food coloring Ice cubes in water Mouthwash Mashed, unpeeled potatoes

Assessment How are a substance and a solution similar? How are they different? When would you use filtration to separate a mixture? When would you use distillation?

Elements and compounds

objective Explain the difference between an element and a compound Distinguish between a substance and a mixture Identify the chemical symbols of elements and name elements given their symbols

Key concepts How are elements and compounds different?* How can substances and mixtures be distinguished?* What do chemists use to represent elements and compounds?*

Elements and compounds Substances are classified as either elements or compounds

element Simplest kind of matter Cannot be broken down any simpler and still have properties of that element All one kind of atom Elements are found on the periodic table

compounds Substance that can be broken down only by chemical methods Made of 2 or more elements chemically combined in fixed proportion When broken down, the pieces have completely different properties than original compound

Element vs. compound Compounds can be broken down into similar substance by chemical means Elements cannot*

Compound vs. mixture Compound Mixture Made of one kind of material Made of more than one kind of material Made by a chemical change Made by a physical change Definite composition Variable composition Water, salt, sugar, hydrogen, carbon Seawater, sugar water, atmosphere

Chemical change A change in which one or more substances are converted into different substance Heat and light are evidence of chemical change

Properties of compounds Different properties than their component elements Due to a CHEMICAL CHANGE, the resulting compound has new and different properties: Table sugar – carbon, hydrogen, oxygen Sodium chloride – sodium, chlorine Water – hydrogen, oxygen

Classification of Matter

Symbols and formulas Currently 117 elements Elements have a 1 or 2 letter symbol and compounds have a formula* Thus formula is made up of more than one symbol Symbol can be the same – O2

Symbols and formulas Elements first letter is always capitalized If there is a second letter it is always lowercase B Ba C Ca

Elements Start looking at element names Table B.7 on page R53 Page 52 Table 2.2 states a few

assessment Classify each of these samples of matter as an element, a compound, or a mixture: Table sugar Cough syrup Tap water Nitrogen

Assessment What elements make up the pain reliever acetaminophen, chemical formula C8H9O2N? Which element is present in the greatest proportion by number of particles?

Chemical reactions

objectives Describe what happens during a chemical change Identify 4 possible clues that a chemical change has taken place Apply the law of conservation of mass to chemical reactions

Key Concepts What always happens duringa chemical change?* What are four possible clues that a chemical change has taken place?* How are the mass of the reactants and the mass of the products of a chemical reaction related?*

Chemical property Ability of substance to undergo a specific chemical change Iron + oxygen = rust Rust is chemical property of iron Once again, during a chemical change the composition of matter always changes*

Chemical reaction One or more substances changes into a new substance 2H2 + O2  2H2O Reactants – what you start with Products – what you make Have different properties than reactants

Recognizing chemical changes Energy – either absorbed or released as heat Color change Gas production – bubbling, fizzing, smoke or odor change Precipitate formation – solid that separates from solution (won’t dissolve) Irreversibility***

Check point What energy transfer takes place when food cooks?

Conservation of mass During a chemical reaction mass of products = mass of reactants* All mass is accounted for: Burning of wood results in products that appear to have less mass as ashes; where is the rest? Carbon dioxide Water vapor

assessment What is the different between physical changes and chemical changes?

Assessment Classify the following changes as physical or chemical changes Water boils Milk turns sour Salt dissolves in water A metal rusts

assessment Hydrogen and oxygen react chemically to form water. How much water would form if 4.8 grams of hydrogen reacted with 38.4 grams of oxygen?