Lesson Objectives

• Define compounds

  • Identify when a substance is a compound

• Calculate the atomic mass of a compound

• Define a mixture

• Identify different types of mixtures

​Introduction

• Elements are the most basic form of matter, but most of the universe is more complex than a single atom

• When we look at more complex forms of matter, there are different categories we can divide them into

What are compounds?

• Compound: a pure substance composed of two or more elements joined together by chemical bonds

  • Can be different elements or multiples of the same

• Compounds are written as chemical formulas that represent the elements in them

  • Use subscripts to tell you the amount of each element

properties of compounds

• Compounds have their own physical and chemical properties that can be used to identify them.

• The properties of a compound are influenced by the elements that make it up, but are not identical.

  • Example: Sodium & Chlorine are extremely reactive elements, but sodium chloride is stable and safe to consume

• Compounds are able to be broken down into their individual elements through the addition of energy to a system

  • Generally heat or electricity

Masses of compounds

• Recall: Every element has an atomic mass

  • Found on the periodic table, generally underneath the elemental symbol

• When elements combine to form compounds, all of those masses add together to give the compound its own mass in amu

• In this class, we will round our atomic masses to whole numbers to keep things simple

Calculating the mass of a compound sample problem 1

• Calculate the mass of water, which has the formula H₂O

  • Step 1: Identify the elements in the compound

    • Hydrogen

    • Oxygen

  • Step 2: Identify how many of each element are in the compound

    • There are two Hydrogens, and one Oxygen

  • Step 3: Add the mass of every atom in the compound together

    • Make sure you count both hydrogen!!

Calculating the mass of a compound sample problem 1

• Calculate the mass of water, which has the formula H₂O

  • Step 1: Identify the elements in the compound

    • Hydrogen

    • Oxygen

  • Step 2: Identify how many of each element are in the compound

    • There are two Hydrogens, and one Oxygen

  • Step 3: Add the mass of every atom in the compound together

    • Make sure you count both hydrogen!!

Calculating the mass of a compound sample problem 2

• Calculate the mass of Sodium Chloride, which has the formula NaCl

  • Step 1: Identify the elements in the compound

    • Sodium

    • Chlorine

  • Step 2: Identify how many of each element are in the compound

    • There is one sodium and one chlorine

  • Step 3: Add the mass of every atom in the compound together

Calculating the mass of a compound sample problem 2

• Calculate the mass of Sodium Chloride, which has the formula NaCl

  • Step 1: Identify the elements in the compound

    • Sodium

    • Chlorine

  • Step 2: Identify how many of each element are in the compound

    • There is one sodium and one chlorine

  • Step 3: Add the mass of every atom in the compound together

Calculating the mass of a compound sample problem 3

• Calculate the mass of Sucrose, which has the formula C₁₂H₂₂O₁₁

  • Step 1: Identify the elements in the compound

    • Carbon

    • Hydrogen

    • Oxygen

  • Step 2: Identify how many of each element are in the compound

Calculating the mass of a compound sample problem 3

• Calculate the mass of Sucrose, which has the formula C₁₂H₂₂O₁₁

  • Step 1: Identify the elements in the compound

  • Step 2: Identify how many of each element are in the compound

    • 12 Carbon

    • 22 Hydrogen

    • 11 Oxygen

  • Step 3: Add the mass of every atom in the compound together

Calculating the mass of a compound sample problem 3

• Calculate the mass of Sucrose, which has the formula C₁₂H₂₂O₁₁

  • Step 1: Identify the elements in the compound

  • Step 2: Identify how many of each element are in the compound

    • 12 Carbon

    • 22 Hydrogen

    • 11 Oxygen

  • Step 3: Add the mass of every atom in the compound together

What are Mixtures?

• Mixture: A combination of two or more substances that are not chemically combined

  • There is no chemical change when a mixture is made, and substances maintain their physical and chemical properties

Types of Mixtures

• Overall, we put mixtures into two broad groups depending on how the mixture appears

• Homogeneous Mixture: A mixture in which all components look like a single substance

• Heterogeneous Mixture: A mixture in which different components can be seen and distinguished

Methods of Separating a mixture

• Most means of separating mixtures involve taking advantage of physical properties and Physical changes

  • magnetism, solubility, etc

• Distillation: A process that separates a mixture based on boiling points

• Filtration: Separating a solid from a liquid using a semipermeable barrier

• Centrifuge: A machine that separates a mixture based on the different densities of the components in the mixture

  • Spins the mixture around so that the most dense particles settle on the bottom, with the least dense on the top

• Chromatography: A means of separating a mixture through a medium based on the different speeds the components can move.

Ratios of Mixtures

• With Compounds, the components will always occur in a fixed ratio

  • Sodium Chloride is always made of one sodium atom and one chlorine atom

• Mixtures do not have fixed ratios and can be adjusted to differing amounts

Solutions

• Solutions are a special type of homogeneous mixture where the particles of the substances are evenly spread out

  • The appearance and properties are the same throughout the mixture

• Solutions are made through the process of dissolving, and are made of two components

  • Solvent: The substance that is present in the largest amount

  • Solute: The substance present in smaller amounts

Types of Solutions

• Water is a common solvent because so many substances dissolve in

  • Also called "The Universal Solvent"

• Many liquids can act as solvents, and some solutes only dissolve in certain solvents

• Gases and solids can also act as solvents by dissolving other substances

  • Alloy: Solid solutions in which a metal is a solvent

Solution Concentration

• Concentration: The amount of solute in a given amount of solvent

• Concentration can be described in two different manners

  • Dilute: A small amount of solute is dissolved

  • Concentrated: A large amount of solute is dissolved

• Concentration can be calculated by dividing the mass of solute by the volume of solvent

  • Generally shown as g/ml

Calculating Concentration Sample Problem 1

• What is the concentration in g/ml of a solution that has 35 g of salt dissolved in 175 ml of Water?

  • Step 1: Identify the variables

    • Mass= 35 grams

    • Volume= 175 ml

  • Step 2: Plug into your equation and solve

Calculating Concentration Sample Problem 2

• What is the concentration in g/ml of a solution that has 90 g of salt (NaCl) dissolved in 3500 ml of Water?

  • Step 1: Identify the variables

    • Mass=

    • Volume=

  • Step 2: Plug into your equation and solve

Calculating Concentration Sample Problem 2

• What is the concentration in g/ml of a solution that has 90 g of salt (NaCl) dissolved in 3500 ml of Water?

  • Step 1: Identify the variables

    • Mass= 90 grams

    • Volume= 3500 ml

  • Step 2: Plug into your equation and solve

Calculating Concentration Sample Problem 3

• What is the concentration in g/ml of a solution that has 70 g of sucrose (C₁₂H₂₂O₁₁) dissolved in 1000 ml of Water?

  • Step 1: Identify the variables

    • Mass=

    • Volume=

  • Step 2: Plug into your equation and solve

Calculating Concentration Sample Problem 3

• What is the concentration in g/ml of a solution that has 70 g of sucrose (C₁₂H₂₂O₁₁) dissolved in 1000 ml of Water?

  • Step 1: Identify the variables

    • Mass= 70

    • Volume=1000

  • Step 2: Plug into your equation and solve

Solubility

• There is a limit to how much solute you can add to a solution

• Solubility: How much solute dissolves in an amount of solvent at a certain temperature

  • For most solids, increasing the temperature increases the amount of solute that can dissolve

    • If the solution becomes cooler, some of the dissolved particles settle out of the solution

Dissolving Gases in Liquids

• Gases can also be dissolved in liquids

• Gases become less soluble at higher temperatures

  • Causes a can of Pop to go flat if you leave it out in warmer temperatures

  • It can affect the amount of Oxygen in water

Dissolving Solids in Liquids

• Solids can be dissolved at different rates based on three different factors

  • Mixing: Moving the particles causes them to spread out more quickly

  • Heating: Increasing the temperature causes particles to move faster and spread out more

  • Crushing: Making particles smaller allows them to mix with the solvent faster

Suspensions

• Suspensions: Mixtures where the particles of material are large enough to settle out

• Particles in a suspension are large enough to scatter or block light

• Can be separated with a filter

Colloids

• Colloid: A mixture in which particles are spread throughout, but are not large enough to settle out.

  • Particle size is between a suspension and a solution

    • Can not be separated with a filter

  • Particles are large enough to scatter light

The Tyndall Effect

• It can sometimes be hard to tell the difference between a solution, suspension, and colloid

• One way to tell is to observe how light passes through the mixture

• The Tyndall Effect occurs when light is scattered by the particles in a colloid