More About Matter

Physical vs. Chemical Properties Physical Properties Physical Properties Observed without changing identity of substance. Observed without changing identity of substance. Ex: color, hardness, density, odor, malleability, ductility, MP temp. Ex: color, hardness, density, odor, malleability, ductility, MP temp. Chemical Properties Chemical Properties Observed during chemical changes Observed during chemical changes Ex: flammable, explosive, corrosive, rusts, decomposes Ex: flammable, explosive, corrosive, rusts, decomposes

Chemical vs. Physical Changes Physical Change Physical Change Does not alter chemical composition. Does not alter chemical composition. Substance still has same chemical formula. Substance still has same chemical formula. Ex: bend, cut, grind, dissolve, undergo a phase change Ex: bend, cut, grind, dissolve, undergo a phase change Chemical Change Chemical Change Chemical composition changes as a reaction occurs. Chemical composition changes as a reaction occurs. New products formed. New products formed. Ex: cook food, sour milk, burn wood, explode dynamite Ex: cook food, sour milk, burn wood, explode dynamite

What Type of Change?

H 2 O(s) → H 2 O(l) H 2 O(s) → H 2 O(l) 2H 2 O (l) → 2H 2 (g) + O 2 (g) 2H 2 O (l) → 2H 2 (g) + O 2 (g) NaCl(s) → NaCl(aq) NaCl(s) → NaCl(aq) CH 4 (g) + O 2 (g) → CO 2 (g) + H 2 O(g) CH 4 (g) + O 2 (g) → CO 2 (g) + H 2 O(g)

Is it Chemical or Physical? Sometimes it is possible to determine a chemical change using the naked eye. Sometimes it is possible to determine a chemical change using the naked eye. Things to look for: Things to look for: Gas bubbles produced, unusual color change, new odor produced, precipitate forms Gas bubbles produced, unusual color change, new odor produced, precipitate forms Precipitate: an insoluble solid that forms when two solutions are mixed. Precipitate: an insoluble solid that forms when two solutions are mixed.

Types of Matter Pure Substance vs. Mixtures

Pure Substances

Elements Made up of atoms of one specific type Made up of atoms of one specific type Have specific physical and chemical properties. Have specific physical and chemical properties. Cannot be broken down by chemical reactions Cannot be broken down by chemical reactions Ex: Fe, K, Na, Si Ex: Fe, K, Na, Si

Compounds Two or more different elements chemically bonded together. Have different chemical and physical properties than elements that make them up. Definite fixed proportions by mass. Ex: C 6 H 12 O 6, MgCl 2, CO 2, NaCl Ex: C 6 H 12 O 6, MgCl 2, CO 2, NaCl

Mixtures

Mixtures Two or more pure substances physically combined. Mixtures can be solid, liquid or gaseous. Mixtures can be solid, liquid or gaseous.

Composition Not Fixed Composition of a mixture is NOT FIXED. Composition of a mixture is NOT FIXED. Can vary depending on how much of each component is added. Can vary depending on how much of each component is added.

Retaining Their Properties Substances in mixtures retain their own properties. Substances in mixtures retain their own properties. Ex: Iron filings (Fe) and sand (SiO 2 ) Ex: Iron filings (Fe) and sand (SiO 2 ) Even if mixed the iron retains its magnetic properties Even if mixed the iron retains its magnetic properties

Clips Mixtures vs. Pure Substances Mixtures vs. Pure Substances aPSM aPSM

Types of Mixtures

Homogeneous Mixtures Components are distributed uniformly at the molecular level. Components are distributed uniformly at the molecular level. All true solutions are homogeneous. All true solutions are homogeneous.

Aqueous = (aq) Aqueous = (aq) dissolved in water or “in solution” If you see (aq) it is a homogeneous mixture If you see (aq) it is a homogeneous mixture Ex: NaCl (aq) Ex: NaCl (aq)

Heterogeneous Mixtures Components are not uniformly distributed at the molecular level. Components are not uniformly distributed at the molecular level. Colloids and suspensions are included in this category. Colloids and suspensions are included in this category.

How to Tell if a True Solution Tyndall Effect Tyndall Effect Suspensions and colloids have larger particles that will scatter a beam of light. In a true solution the light will not be scattered Suspensions and colloids have larger particles that will scatter a beam of light. In a true solution the light will not be scattered

Techniques to Separate Mixtures

Separating Mixtures Components retain their own properties, so use these properties to separate them. Components retain their own properties, so use these properties to separate them. Ex: density, particle size differences, solubility differences, BP temperature, magnetic properties Ex: density, particle size differences, solubility differences, BP temperature, magnetic properties

Filtration Ex: Separate water & sand Ex: Separate water & sand Can be used to separate heterogeneous mixtures Can be used to separate heterogeneous mixtures Technique cannot be used to separate components of solutions Technique cannot be used to separate components of solutions

Separatory Funnel Ex: Separate oil and water Ex: Separate oil and water What type of mixture? What type of mixture?

Evaporation Ex: Separate sugar from water Ex: Separate sugar from water What type of mixture? What type of mixture?

Chromatography Solvent runs up paper and components separate out along length of paper depending on level of attraction to solvent. Solvent runs up paper and components separate out along length of paper depending on level of attraction to solvent. Ex: Separate different types of chlorophyll Ex: Separate different types of chlorophyll

Distillation Separates two or more liquids, due to differences in boiling point temp. Separates two or more liquids, due to differences in boiling point temp. Ex: Separate alcohol and water Ex: Separate alcohol and water What type of mixture? What type of mixture?

Clips Separating Mixtures Separating Mixtures Distillation Distillation

Density Calculating

Density Because all matter has mass and volume, all matter has density. Because all matter has mass and volume, all matter has density. No matter the size of the sample, the density doesn’t change. No matter the size of the sample, the density doesn’t change. It is a physical property. It is a physical property. See Reference Table S for the density of elements. See Reference Table S for the density of elements. D = M V

Density of Water Density of Pure Water = 1.0 g/ml Density of Pure Water = 1.0 g/ml If a substance has a density greater than water it will sink, if not it will float. If a substance has a density greater than water it will sink, if not it will float. When you dissolve a substance in water it makes it more dense. When you dissolve a substance in water it makes it more dense

Measuring Density (D = M/V) Mass Mass Measured on a scale, often you need to use a weighing dish or a beaker. Measured on a scale, often you need to use a weighing dish or a beaker. Volume Volume Can be measured in different ways. Can be measured in different ways. For solids the method of water displacement is often used. For solids the method of water displacement is often used.

Density column Density column Coke vs Diet coke Coke vs Diet coke

Cool Clips Chemical Reactions (Bill Nye) Chemical Reactions (Bill Nye) Steve Spangler (clock reactions) Steve Spangler (clock reactions) Diet Coke and Mentos Diet Coke and Mentos