Chapter 18: How Chemicals Mix BIG IDEA: Most everything is a mixture

18.1 Most Materials are Mixtures Mixture- a combination of 2 or more substances in which each substance retains its own properties. -Each substance in a mixture maintains its chemical identity Most materials we encounter are mixtures, of elements, compounds, or of elements with compounds. Our atmosphere is a mixture of N,O, Ar, CO2, H2O. Tap water also has other cmpnds such as: Ca, Mg, Cl, F, Fe, K which helps to destroy bacteria and promote health. Since substances in a mixture maintain their identity it is a PHYSICAL change (easy to reverse)

The components of mixtures can be separated from one another by using differences in their physical properties. -Differences in: state of matter, density, boiling/melting points Ex: filtration: separating a solid/liquid mixture via filter paper Ex: distillation: separating a solid/liquid mixture via heating Ex of filtration: how coffee is made, separating salt water. Distillation, separating salt water

18.2 Chemist’s Classification of Matter Pure materials consist of a single element or compound Impure materials are a mixture of 2+ elements or compounds Classification of mixtures: Heterogeneous vs. Homogenous Uneven composition throughout Even composition throughout

Homogenous mixtures can be solutions or suspensions Solution: All components are in the same phase Suspension: Different components are in different phases -The easiest way to tell the 2 apart is to spin in centrifuge Solution: all solid/liquid or gas, no combo. Components of a solution are no so readily distinguished. Centrifuges separates the components of suspensions, but not solutions

18.3 Making Solutions Solutions aren’t always liquids (gemstones=solid, air=gas) In solutions the component present in the largest amount is the solvent, all other components are solutes. Ex: Salt water. Water= solvent b/c substance is dissolved in it Salt= Solute, it’s the component being dissolved

There is a limit to how much of a solute can be dissolved. -In saturated solutions no more solute can be dissolved -Unsaturated solutions have not yet reached their dissolving limit In saturated solutions the solute can no longer be mixed evenly, and the components of a mixture take on different phases of matter

Identify solvent vs. solute Which is solvent, which is solute? Salt water Air (A solution of 78% N2, 21%O2 and various other gases) Bronze (95% Cu, 5% Sn) Kool-Aid

18.4 Concentration and the Mole Something that is less concentrated is more watered down A mole of any type of particles = 6.02 ∙1023 molecules Avogadro's number A mole is like inferring that a couple=2, a dozen=12. A mole is a very large number, but they are used in chemistry b/c molecules are so small. Number of grams in a solution tells you the mass of a solute in a given solution, whereas the number of moles in a given solution actually tells you how many molecules are in a solution. Avogadro’s number is named after the Italian scientists Amedeo Avagadro, who proposed that the volume of a gas is proportional to the number of atoms of molecules of that gas

Molarity= # 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝐿 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 Another common unit of concentration used by chemists: Molarity= # 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝐿 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 1 molar solution= 1M= 1 mole/L solution - Higher molarity=higher saturation= higher concentration. Molarity tells us how saturated a solution is. Higher molarity=higher saturation= higher concentration. When working with dangerous chemicals it is very important to know the concentration of a substance

18.5 Solubility Solubility= ability of a solute to dissolve in a solvent. Can dissolve= soluble Can NOT dissolve= insoluble -Solubility depends on the microscopic attractions between solute particles and solvent particles Do you think that substances w/ great attractive forces dissolve more or less easily? (more!)

Solubility increases w/: Increased temperatures (More kinetic energy, particle movement increases) Broken into smaller pieces or being stirred. (More surface area [amount of space something takes up] comes into contact w/ the solvent

18.6 Soaps and Detergents Soap works b/c it has both nonpolar and polar properties _Polar heads are attracted to nonpolar grime. The nonpolar tails are attracted to water, so this allows the soap + water to flow and get the grime off. Detergents=stronger grease penetration

Purifying the Water we Drink We purify water by taking advantage of the differences in physical properties of water and the solutes/particles it contains Take groundwater/ lake/river water and remove pathogens by mixing w/ chemicals. The impurities clump together and settle @ bottom Water is filtered People also make drinking water by boiling the source water