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Chapter 3. Physical and Chemical Properties Physical and Chemical Changes. Physical Properties. Physical properties can be observed or measured without changing the composition of matter.
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Chapter 3 Physical and Chemical Properties Physical and Chemical Changes
Physical Properties • Physical properties can be observed or measured without changing the composition of matter. • Physical properties include: appearance, texture, color, odor, melting point, boiling point, density, solubility, and many others.
What do you think this is?What physical properties can be “observed”?
Physical Properties • Physical State: Solid • Description: • Grayish metal. • Melting Point: 922K 649°C 1200°F Boiling Point: 1363K 1090°C 1994°F • Density: 1.738g/cm3 • Specific Heat: 1.02J/g∙°C
Chemical Properties • Chemical properties of matter describe how a substance reacts to form a new substance(s).
Chemical Properties • “Reactivity” is really the only chemical property. Anything that describes how a substance reacts is a chemical property. • For example hydrogen is explosive.
Chemical Properties • Reacts slowly with water to form a base. • Reacts violently with acid forming hydrogen gas. • Reacts with carbon dioxide producing an intense light.
Chemical Properties Magnesium reacting with dry ice.
Physical Changes • A physical change takes place without any changes in composition. • The same element or compound is present before and after the change.
Chemical Changes or Reactions • Chemical changes result in one or more substances of entirely different composition from the original substances. • The atoms at the start of the reaction are rearranged into new substances.
Sucrose (sugar) reacts with sulfuric acid. • Sucrose (sugar) reacts with sulfuric acid creating carbon and water. • C12H22O11 + H2SO4 → different substances
Physical Change Chemical Change Changes of State are physical changes but can accompany a chemical change. Precipitate
Precipitate • A solid insoluble substance that forms when solutions are mixed.
Separation Techniques for Mixtures • Distillation • Fractional Crystallization
Distillation • Distillation is used to separate parts of a mixture that have different boiling points. • Distillation is the process of heating a liquid until it boils, capturing and cooling the resultant hot vapors, and collecting the condensed vapors.
Fractional Crystallization • Separates different solutes from a solution based on differences in their solubility. • A process by which a chemical compound is separated by crystallization.
What is the solubility of KNO3 at 80ºC? ≈ 160g KNO3 per 100 g water
At what temperature is the solubility of KBr equal to 60g/100g H2O? ≈ 10°C
Homework • Chapter 3 Worksheet 3-1