Mixture
• Two or more substances that are not chemically combined
• All mixtures can be physically separated• Ways to separate mixtures
– Distillation-use boiling point– Magnet-uses magnetism– Centrifuge-use density– Filtering-separates large particles from
smaller ones
• Ratio of mixtures are not fixed• Substances keep their identities• Mixtures can be solid, liquid or gas• Examples of mixtures
– Chex mix– Raisin bran– Pizza– Mixed nuts– air
Solutions
• Mixture that appears to be a single substance
• Material is evenly distributed by dissolving
• Material must be soluble (able to dissolve)
• Solute is what is dissolved
• Solvent what the solute is dissolved in
• Water is the universal solvent
• Materials that will not dissolve (insoluble) forms a mixture that is not a solution
• Examples of solutions– Sodas– Gasoline– Ice tea– Salt water– Kool aid
• In solutions the particles are so small they never settle out (sink to bottom), can’t scatter light nor can they be filtered
• Solubility is the ability of substances to dissolve at a given temperature and pressure
• How much of a solute a solvent can hold is the concentration (grams of solute/milliliter of solvent, g/mL)
• To increase solubility you can change temperature, crush, stir, shake
• Homogenous solutions– meaning the same
• Heterogenous solutions– meaning different
Suspensions
• Suspensions are mixtures where the particles are heavy enough to settle out (sink to bottom) of the solution, scatter light, can be filtered
• Examples of suspensions– Snow globe– Italian dressing
Colloids
• Colloids are mixtures where the particles are evenly dispersed but are not heavy enough to settle out, can scatter light, can’t be filtered
• Examples of colloids– Mayo– Whip cream– pudding
Elements
• elements are pure substance that can not be separated into simpler substances by physical or chemical means
• Pure substance is a substance with only one type of particle called atoms
• All atoms of an element are identical regardless of how much you have
• Elements can be identified by their characteristic properties
• The properties, both chemical and physical do not depend on the amount of the element present
• Elements can have similar properties but each element has some property that makes it unique
• Elements are classified by categories
• Metals – shiny, good conductors
• Nonmetals – dull, poor conductors
• Metalloids –has properties of metals and nonmetals depending on conditions
• Categories allow unknown elements to be placed in the periodic table based on similar properties
Compounds
• Pure substance composed of two or more elements that are chemically combined
• Compounds are formed by elements reacting or having a chemical change
• A particle of a compound is a molecule• Elements do not form compounds
randomly• All compounds are formed from only the
elements on the periodic table
• Compounds form in specific mass ratio
• Ex: mass of hydrogen to mass oxygen in water is hydrogen 1 to oxygen 8 which can be written as 1:8. For every molecule of water, the ratio is the same, if the ratio is different, then the compound can not be water
• When elements form compounds, new characteristics properties are created
• Compounds have properties that differ from the elements that formed them
• Na (sodium) reactive alkali metal + Cl (chlorine) poisonous gas → NaCl (table salt)
• Some compounds can be broken down into their elements by a chemical change
• Other compounds break down into simpler compounds instead of elements
• The only way to separate a compound into elements or other compounds is by a chemical reaction which allows for a chemical change
• Two ways: is to apply energy or electric current
• Common compounds
• Salt, sugar, water
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