Matter

Properties of Matter Two classes of properties: Physical Chemical Physical: observable without changing composition of substance Chemical: only observed if a change in composition occurs

Properties of Matter cont… Two types of physical properties: Extensive Intensive Extensive: properties that depend on the amount of material is present Intensive: depends on the identity of the substance only, not the amount present

Physical Changes A change of matter from one form to another without changing the substance itself. Examples: phase changes, mixtures Heating Curves: Lab

Chemical Changes Entirely new substances with different properties A + B  C (reactants go to products)

An Unexpected Color Change Release or Absorption of Energy Formation of a Precipitate (solid) Formation of a gas

Chemical or Physical Frying an egg Boiling Water Sanding a wooden plank Digesting food Popping a balloon Chemical Physical

Properties and Changes Practice Properties: identify each as chemical or physical Silver tarnishes Copper can be pounded into a bowl Helium is unreactive Barium melts at 725°C Potassium metal reacts violently with water Changes: identify each as chemical or physical Water condensates Electricity changes water into hydrogen and oxygen Yeast cells in bread make carbon dioxide and ethanol from sugar Wood burns Copper wire turns green over time

ATOM Atom – the smallest unit of an element that maintains the properties of that element.

Pure Substance A sample of matter, either a single element or a single compound, that has definite chemical and physical properties Figure 14, Page 22

Elements A pure substance All atoms of the same element have the same atomic number

Two or more different elements joined by chemical bonds. Compounds A pure substance Two or more different elements joined by chemical bonds.

The smallest unit of a substance Molecules The smallest unit of a substance Has physical and chemical properties of that substance.

All of the following are molecules, but are they compounds or elements? Br2 H2O O2 O3 C12H22O12 Element Compound Element Element Compound

Mixtures A combination of two or more substances Not chemically combined Examples are air, ice tea, and even cake batter Proportions can vary

Homogeneous Mixtures Uniform distribution Same proportions of ingredients Examples: Gasoline, air, and syrup

Heterogeneous Mixtures Not uniformly distributed. Different proportions. Examples: Chocolate chip cookie dough, vegetable soup and granite.

Homogeneous and Heterogeneous Mixtures

Classification Practice Classify the following as either a pure substance or a mixture. If a pure substance, is it an element or a compound? If a mixture, homogeneous or heterogeneous? Concrete Hamburger Sucrose (table sugar) Copper Diamond Copper (II) oxide Saltwater Milk Dry ice (solid CO2) Vitamin C

States of Matter

There are Four States of Matter Solid Liquid Gas

Solids Particles are very close together Have orderly, fixed arrangements Fixed volumes Particles can only vibrate in position

Liquids More random than solids. Particles are loosely held together, but can move past one another. Liquids can flow into any shape. Definite volume.

Attractive forces between liquid particles may result in: Cohesion Attraction for each other Adhesion Attraction to other materials Capillary Action Ability to “climb” due to cohesion and adhesion Surface Tension Force that act on the surface of a liquid and that tends to minimize the area of the surface

Gas Essentially independent particles. Large space between particles little to no attraction between particles. Gases can flow into any shape No definite volume

Changing States Condensation Deposition Sublimation Evaporation Melting Freezing

Heating Curves Show the temperature in a substance when that substance is being given more heat energy.

Since mixtures are just physically combined, they can be separated. Separating Mixtures Since mixtures are just physically combined, they can be separated.

Separating Mixtures Filtering – separation through differences in particle size Decanting –separating by pouring Distillation –separate two liquids based on differences in boiling points Evaporation – removing a liquid to leave a solid Chromatography – Separates by using a mobile phase and a stationary phase