Physical & Chemical Properties of Matter

Matter Matter: anything that has mass and takes up space Chemistry: the study of matter Property: attribute, quality, or characteristic of something Matter has both physical and chemical properties

Properties of Matter Physical Properties: describe the look or feel of a substance, such as color, hardness, density, texture, and phase Can change when conditions change, but the substance remains the same Chemical Properties: characterize ability of a substance to react with other substances or transform from one substance to another – flammability, reactivity, heat of combustion, and toxicity Chemical Bonds: the attractions between atoms that hold them together in a molecule

Density Density: ratio of mass to volume for an object D=m/v (density = mass/volume) Density of a pure compound or element is a constant Gold is always 19.3 g/mL; water is always 1.0 g/mL Less dense objects float in more dense objects

Viscosity Viscosity: A material’s resistance to flow Physical property A liquid with high viscosity would be honey, one with low viscosity would be water Newton stated the only way to change a fluid’s viscosity is to alter its temperature—honey flows more easily when you add heat to it.

Changes in Matter Physical Change: a substance changes its phase or some other physical property but NOT its chemical composition a piece of paper being cut in half If it is a physical change, restoring the original conditions will restore the original substance If you freeze liquid water and then allow the ice to melt, you will again have liquid water

Changes in Matter Common signs of a physical change Texture—rough wood vs. finished wood Color—painting a car Shape—folding a piece of paper Change of state—boiling water

Changes in Matter Chemical Change: any change in a substance that involves a rearrangement of the way atoms are bonded baking soda reacts with vinegar to form carbon dioxide and water If it is a chemical change, restoring the original conditions will NOT restore the original substance If I make cookies from sugar, eggs, and flour, there is nothing I can do to the cookies to get back my original ingredients

Changes in Matter Common signs of a chemical change Color—metal rusting Noticeable odor—rotten egg; spoiled milk Formation of precipitate—a solid that forms inside of a solution or another solid Formation of bubbles— indicates a formation of a gas

Matter Matter is either pure or impure Pure Substance: matter that has a fixed composition (make-up) and definite (unchanging) properties

Atoms & Elements Atom: smallest unit of matter, make up everything around you! Element: material made up of one type of atom, cannot be broken down by any means, organized in the periodic table All elements are listed in the periodic table and given an atomic symbol (1-2 letters) Both are pure substances

Compounds Elements can combine to form compounds, another example of a pure substance Compounds: form when atoms of two or more different elements bond together Properties of compounds are different than their elemental components Compounds are represented with chemical formulas which indicate the atoms present and their proportions

Compounds In a chemical formula, subscripts tell us the ratio in which the atoms combine NaCl = 1 sodium atom for every chlorine atom NH3 = 3 hydrogen atoms for every 1 nitrogen atom Compounds are named according to which elements they contain

Compounds 1. metal + nonmetal Element farther to the left is first, followed by element farther to the right, with the suffix –ide added to its name NaCl = sodium chloride 2. nonmetal + nonmetal Add prefixes based on the number of atoms in the element 1 (mono-), 2 (di-), 3 (tri-), 4 (tetra-) CO2 = carbon dioxide 3. systematic names Many compounds are assigned common names NH3 = ammonia

Mixtures Mixture: a combination of two or more substances in which each retains its own properties. THEY ARE NOT CHEMICALLY BONDED Mixtures are not pure substances Most materials are mixtures

Mixtures Heterogeneous: a mixture in which you can see the different components as individual substances Sand in water; oil and water; pulp in orange juice Homogeneous: a mixture in which the composition is the same throughout Air, salt water Are either solutions or suspensions

Mixtures Solution: all of the components in the mixture are in the same phase Air is made of gaseous N2 and O2 Saltwater is a liquid solution – water and dissolved sodium chloride are found in a single liquid phase Suspension: the particles of a substance are finely mixed but not dissolved Milk is a mixture of proteins and fats in water Blood is a mixture of blood cells in water

Periodic Table Elements are organized in the periodic table by their properties Metals are shiny, opaque, good conductors of electricity and heat, and mostly solid at room temperature Nonmetals are nonmetallic, poor conductors of electricity and heat, may be transparent, and can be either solid, liquid, or gas at room temperature Metalloids have both metallic and nonmetallic properties—include 6 elements: boron, silicon, germanium, arsenic, antimony, and tellurium

Periodic Table The three main groups of the periodic table are further divided into families Period: horizontal row Periodic Trend: gradual change in elemental properties across a period Group (family): vertical column Down any group, the properties are very similar