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Matter. States of Matter Density Physical and Chemical Properties Physical and Chemical Changes Law of Conservation of Mass Pure Substances Mixtures Acids and Bases. Everything that has mass and volume is called matter. What is matter?. Mass vs. Weight.
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Matter States of Matter Density Physical and Chemical Properties Physical and Chemical Changes Law of Conservation of Mass Pure Substances Mixtures Acids and Bases
Everything that has mass and volume is called matter. What is matter?
Mass vs. Weight Mass is a measurement of how much “stuff” is in an object. Mass is constant for a given object Weight is a measure of how much the gravity on our planet pushes an object towards its surface. Weight changes depending on altitude.
What kind of properties does matter have? physical properties chemical properties These changes can be macroscopic,microscopic, or submicroscopic.
Macroscopic: Microscopic: Submicroscopic:
States of Matter • Solids • Liquids • Gases
Solids • Have a definite shape • Have a definite volume • Generally rigid Particles vibrate close together with very little movement.
Liquids • Have an indefinite shape, so • are fluid. • Have a definite volume. Liquid particles vibrate and rotate around each other.
Gases • Have an indefinite shape and • volume • Fluid and compressible Particles vibrate, rotate, and move randomly through mostly empty space.
What is a physical property? A physical property can be determined by your senses or by measuring.
Physical Properties • Physical properties can be divided into two kinds, intensive and extensive. • Intensive properties may be used for identification of unknowns because they do not change with amount. • Extensive properties depend on amount.
Intensive Physical Properties • Density • Heat conductivity • Color • Index of refraction • Malleability • Electrical • Conductivity • Boiling point • Melting point • Ductility
Physical: Density Density is a ratio that compares the mass of an object to its volume. Density = Mass Volume
Practice Problem Suppose a sample of aluminum is placed in a 25 mL graduated cylinder containing 10.5 mL of water. The level of the water rises to 13.5 mL. What is the mass of the aluminum sample? The density of aluminum is 2.7 g/mL. Known Unknown Density = 2.7 g/mL mass = ? Volume = 13.5 – 10.5 = 3.0 mL M Formula: density = mass/volume or D = V
Suppose a sample of aluminum is placed in a 25 mL graduated cylinder containing 10.5 mL of water. The level of the water rises to 13.5 mL. What is the mass of the aluminum sample? The density of aluminum is 2.7 g/mL. m = D x V m m = 2.7 x 3.0 D V m = 8.1 grams
Which are intensive properties? • Color • Boiling point • Density • Melting point • Malleability • Ductility • Conductivity
Which are extensive properties? • Mass • Volume • Shape of material
What is a chemical property? A chemical property involves a permanent change or reaction.
What are chemical properties? • Reaction with acid • Reaction with water • Reaction with oxygen • Reaction with base • Ability to burn
What kind of changes can matter undergo? Physical Chemical Ask yourself, is the change permanent? Does the matter keep its original properties?
What is a physical change? A physical change is a change that does not change the identity of a substance.
Phase Changes Melting Freezing Cutting Dissolving Breaking Mixing Tearing Typical Physical Changes Ask yourself: Does the identity of the substance change or is it just in a different form?
What is a Chemical Change? A chemical change is a change that produces new products. Chemical changes cannot be reversed by physical means or chemical means in some cases.
Reaction with acids Reaction with bases Reaction with oxygen or air Rusting Burning Reaction with other elements Decomposition Corrosion Spoiling Cooking Characteristic Chemical Changes
How do you know if a chemical change has occurred? Look for one or more of the following: • Production of a gas • Production of a precipitate • Permanent change in color • Change in temperature • Change in smell
Law of Conservation of Matter The mass of the reactants before a reaction is equal to the mass of the products after the reaction. In other words, matter cannot be created nor destroyed. It is just converted from one form to another
Law of Conservation of Matter Reactants—the chemicals that react in a chemical change. They are always on the left side of a chemical equation. 2H2 + O2→ 2H2O
Law of Conservation of Matter Products—the chemicals that are formed in a chemical change. They are always on the right side of a chemical equation. 2H2 + O2→2H2O
Practice Problem • A 10 g sample of magnesium reacts with oxygen to form 16.6 g of magnesium oxide. How many grams of oxygen reacted? Magnesium + Oxygen → Magnesium oxide 10 g + ___ g = 16.6 g
Kinds of Matter Mixtures And Pure substances
Characteristics of Pure Substances • Fixed composition • Cannot be separated into simpler substances by physical methods (physical changes) • Can only be changed in identity and properties by chemical methods • Properties do not vary
Compounds Definite Ratio Decomposed by chemical change Elements Cannot be decomposed by any changes What is a pure substance?
What is a mixture? Mixtures are two or more substances that are NOT chemically combined. Mixtures do not have: · constant boiling points · constant melting points
Characteristics of Mixtures • Variable composition • Components retain their characteristic properties • May be separated into pure substances by physical methods • Mixtures of different compositions may have widely different properties
Homogenous Mixtures • Also known as solutions. • Look the same throughout • Separated by physical means • Don’t scatter light Can’t tell by looking that they are a mixture.
Heterogenous Mixtures • Different components are visible to the eye • Easily separated by physical means • Composition varies
