COMPOSITION OF MATTER

Objectives Understand that God created all things on Earth using 91 elements Distinguish between pure substances and mixtures Distinguish between compounds, elements, and mixtures State the basic properties that all mixtures share Distinguish between heterogeneous mixtures and homogeneous mixtures Separate mixtures using various methods Distinguish between a colloid and a suspension. Distinguish between a physical and chemical properties. Distinguish between a physical and chemical change.

Element Pure substance One kind of atom Represented by 1 or 2 letter symbol (the first letter will always be capitalized, the second lower case) Examples: Helium ( He ), oxygen ( O2 ), copper (Cu) Categorized on the periodic table God created everything with 91 elements. Man has create more since.

Compound 2 or more elements are chemically combined Represented by a chemical formula. The formula shows what elements are in the compound & how many atoms of each element are present. Examples: sodium chloride (NaCl), water (H2O). Combine in same proportion Cannot be separated physically, must be separated by a chemical reaction.

Mixture two or more substances physically combined Do not combined in some proportion Can be separated by physical means Heterogeneous mixture – not uniform (examples include: ocean, muddy water, air) Homogeneous mixture (aka solutions) - uniform (examples include: soda, salt water, brass, bronze) Alloy : mixture of two or more metals or a metal and a non-metal

Difference between a compound and a mixture…..

Physical Properties Physical properties can be observed without chemically changing matter. This means we do not need to have a chemical reaction to observe it.. Examples: color, shape, smell

Chemical Properties Chemical properties describe how a substance reacts with other substances. Examples: Reactivity : how a substance reacts with other substances Corrotion: metals easily corrode, so we paint them Combustibility: it will burn – like wood Flammability: it will ignite easily – gasoline is both flammable and combustible

Physical or Chemical? Color Texture Acidity Solubility Ability to rust Mass Phase Changes

Physical or Chemical? Color - physical Texture - physical Acidity - chemical Solubility - physical Ability to rust - chemical Mass - physical Phase Changes – physical Solubility: how one substance dissolves in another without chemically changing.

Physical Changes No change in identity of the substance At the molecular level, the substance remain the same Examples: breaking, tearing, phase changes

Chemical Changes Chemical Change: one or more substances produced. One or more substances are converted into one or more different substances. Examples: rusting, burning, forming salt from sodium and chlorine.

Physical or Chemical Change? Digesting Food Evaporation Tarnishing Breaking glass Burning wood

Physical or Chemical Change? Digesting Food - chemical Evaporation - physical Tarnishing - chemical Breaking glass - physical Burning wood - chemical

Suspensions and Colloids Mixture Particles will settle. Partlicles are large enough to block light. Examples: salad dressing, sand water, snow globe. Colloid: Particles will not settle. Scatter light.