1. Quarter Three Notes

2. 1.1 - Molecules Matter Chemistry is the study of matter.
Matter is made up of extremely tiny particles called atoms and molecules.
Atoms and molecules make up the three common states of matter on Earth— solids, liquids, and gases.
The particles of a liquid are attracted to one another, are in motion, and are able to move past one another.
Being a solid, liquid, or gas is a property of a substance.
ACS Lesson 1.1 :

3. 1.2 -Molecules in Motion
Heating a liquid increases the speed of the molecules.
An increase in the speed of the molecules competes with the attraction between molecules and causes molecules to move a little further apart.
Cooling a liquid decreases the speed of the molecules.
A decrease in the speed of the molecules allows the attractions between molecules to bring them a little closer together.
ACS Lesson 1.2 :

4. 1.3 -The Ups and Downs of Thermometers
The way a thermometer works is an example of heating and cooling a liquid.
When heated, the molecules of the liquid in the thermometer move faster, causing them to get a little further apart. This results in movement up the thermometer.
When cooled, the molecules of the liquid in the thermometer move slower, causing them to get a little closer together. This results in movement down the thermometer.
ACS Lesson 1.3 :

5. 1.4 -Moving Molecules in a Solid
In a solid, the atoms are very attracted to one another. The atoms vibrate but stay in fixed positions because of their strong attractions for one another.
Heating a solid increases the motion of the atoms.
An increase in the motion of the atoms competes with the attraction between atoms and causes them to move a little further apart.
Cooling a solid decreases the motion of the atoms.
A decrease in the motion of the atoms allows the attractions between atoms to bring them a little close together.
ACS Lesson 1.4 :

6. 1.5 - Air – It’s Really There
In a gas, the molecules have very weak attractions for one another. Molecules are able to move freely past each other with little interaction between them.
The molecules of a gas are much more spread out and move independently compared to the molecules of liquids and solids.
Whether a substance is a solid, liquid, or gas at a certain temperature depends on the balance between the motion of the atoms or molecules at that temperature and how strong their attractions are for one another.
Heating a gas increases the speed of its molecules.
Cooling a gas decreases the speed of its molecules.
ACS Lesson 1.5:

7. 2.1 - Heat, Temperature, and Conduction
Adding energy (heating) atoms and molecules increases their motion, resulting in an increase in temperature.
Removing energy (cooling) atoms and molecules decreases their motion, resulting in a decrease in temperature.
Energy can be added or removed from a substance through a process called conduction.
In conduction, faster-moving molecules contact slower-moving molecules and transfer energy to them.
During conduction the slower-moving molecules speed up and the faster- moving molecules slow down.
Temperature is a measure of the average kinetic energy of the atoms or molecules of a substance.
Heat is the transfer of energy from a substance at a higher temperature to a substance at a lower temperature.
Some materials are better conductors of heat than others.
ACS Lesson 2.1:

8. 2.2 - Changing State: Evaporation
Evaporation occurs when molecules in a liquid gain enough energy that they overcome attractions from other molecules and break away to become a gas.
Adding energy increases the rate of evaporation.
To conduct a valid experiment, variables need to be identified and controlled.
ACS Lesson 2.2:

9. 2.3 -Changing State: Condensation
Condensation is the process in which molecules of a gas slow down, come together, and form a liquid.
When gas molecules transfer their energy to something cooler, they slow down and their attractions cause them to bond to become a liquid.
Making water vapor colder increases the rate of condensation.
Increasing the concentration of water vapor in the air increases the rate of condensation.
ACS Lesson 2.3:

10. 2.4 - Changing State: Freezing
Freezing is the process that causes a substance to change from a liquid to a solid.
Freezing occurs when the molecules of a liquid slow down enough that their attractions cause them to arrange themselves into fixed positions as a solid.
ACS Lesson 2.4:

11. 2.5 - Changing State: Melting
Melting is a process that causes a substance to change from a solid to a liquid.
Melting occurs when the molecules of a solid speed up enough that the motion overcomes the attractions so that the molecules can move past each other as a liquid.
ACS Lesson 2.5:

12. 3.1 - What is Density?
Density is a characteristic property of a substance.
The density of a substance is the relationship between the mass of the substance and how much space it takes up (volume).
The mass of atoms, their size, and how they are arranged determine the density of a substance.
Density equals the mass of the substance divided by its volume; D = m/v.
Objects with the same volume but different mass have different densities.
ACS Lesson 3.1:

13. 3.2 - Finding Volume: The Water Displacement Method
A submerged object displaces a volume of liquid equal to the volume of the object.
One milliliter (1 mL) of water has a volume of 1 cubic centimeter (1cm3).
Different atoms have different sizes and masses.
Atoms on the periodic table are arranged in order according to the number of protons in the nucleus.
Even though an atom may be smaller than another atom, it might have more mass.
The mass of atoms, their size, and how they are arranged determine the density of a substance.
Density equals the mass of the object divided by its volume; D = m/v.
Objects with the same mass but different volume have different densities.
ACS Lesson 3.2:

14. 3.3 - The Density of Water
Just like solids, liquids also have their own characteristic density.
The volume of a liquid can be measured directly with a graduated cylinder.
The molecules of different liquids have different size and mass.
The mass and size of the molecules in a liquid and how closely they are packed together determine the density of the liquid.
Just like a solid, the density of a liquid equals the mass of the liquid divided by its volume; D = m/v.
The density of water is 1 gram per cubic centimeter.
The density of a substance is the same regardless of the size of the sample.
ACS Lesson 3.3:

15. 3.4 - Density – Sink and Float for Solids
The density of an object determines whether it will float or sink in another substance.
An object will float if it is less dense than the liquid it is placed in.
An object will sink if it is more dense than the liquid it is placed in.
ACS Lesson 3.4:

16. 3.5 -Density – Sink and Float for Liquids
Since density is a characteristic property of a substance, each liquid has its own characteristic density.
The density of a liquid determines whether it will float on or sink in another liquid.
A liquid will float if it is less dense than the liquid it is placed in.
A liquid will sink if it is more dense than the liquid it is placed in.
Oil
Water
Alcohol
ACS Lesson 3.5:

17. 3.6 - Temperature and Density
Heating a substance causes molecules to speed up and spread slightly further apart, occupying a larger volume that results in a decrease in density.
Cooling a substance causes molecules to slow down and get slightly closer together, occupying a smaller volume that results in an increase in density.
Hot water is less dense and will float on room-temperature water.
Cold water is more dense and will sink in room-temperature water.
ACS Lesson 3.6:

18. 4.1 - Protons, Neutrons, and Electrons
Atoms are made of extremely tiny particles called protons, neutrons, and electrons.
Protons and neutrons are in the center of the atom, making up the nucleus.
Electrons surround the nucleus.
Protons have a positive charge.
Electrons have a negative charge.
The charge on the proton and electron are exactly the same size but opposite.
Neutrons have no charge.
Since opposite charges attract, protons and electrons attract each other.
ACS Lesson 4.1:

19. 4.2 -The Periodic Table
The periodic table is a chart containing information about the atoms that make up all matter.
An element is a substance made up of only one type of atom.
The atomic number of an atom is equal to the number of protons in its nucleus.
The number of electrons surrounding the nucleus of an atom is equal to the number of protons in its nucleus.
Different atoms of the same element can have a different number of neutrons.
Atoms of the same element with different numbers of neutrons are called “isotopes” of that element.
The atomic mass of an element is the average mass of the different isotopes of the element.
The atoms in the periodic table are arranged to show characteristics and relationships between atoms and groups of atoms.
ACS Lesson 4.2:

20. 4.3 -The Periodic Table and Energy Level Models
The electrons surrounding an atom are located in regions around the nucleus called “energy levels.”
An energy level represents the 3-dimensional space surrounding the nucleus where electrons are most likely to be.
The first energy level is closest to the nucleus. The second energy level is a little farther away than the first. The third is a little farther away than the second, and so on.
Each energy level can accommodate or “hold” a different number of electrons before additional electrons begin to go into the next level.
When the first energy level has 2 electrons, the next electrons go into the second energy level until the second level has 8 electrons.
When the second energy level has 8 electrons, the next electrons go into the third energy level until the third level has 8 electrons.
When the third energy level has 8 electrons, the next 2 electrons go into the fourth energy level.
The electrons in the energy level farthest from the nucleus are called valence electrons.
Atoms in the same column (group) in the periodic table have the same number of valence electrons.
ACS Lesson 4.3:

21. 4.4 -Energy Levels, Electrons, and Covalent Bonds
The electrons on the outermost energy level of the atom are called valence electrons.
The valence electrons are involved in bonding one atom to another.
The attraction of each atom’s nucleus for the valence electrons of the other atom pulls the atoms together.
As the attractions bring the atoms together, electrons from each atom are attracted to the nucleus of both atoms, which “share” the electrons.
The sharing of electrons between atoms is called a covalent bond, which holds the atoms together as a molecule.
A covalent bond happens if the attractions are strong enough in both atoms and if each atom has room for an electron in its outer energy level.
Atoms will covalently bond until their outer energy level is full.
Atoms covalently bonded as a molecule are more stable than they were as separate atoms.
ACS Lesson 4.4:

22. 4.5 -Energy Levels, Electrons, and Ionic Bonds
The attractions between the protons and electrons of atoms can cause an electron to move completely from one atom to the other.
When an atom loses or gains an electron, it is called an ion.
The atom that loses an electron becomes a positive ion.
The atom that gains an electron becomes a negative ion.
A positive and negative ion attract each other and form an ionic bond.
ACS Lesson 4.5:

23. 4.6 -Represent Bonding with Lewis Dot
There are shorthand ways to represent how atoms form covalent or ionic bonds.
Lewis dot diagrams use dots arranged around the atomic symbol to represent the electrons in the outermost energy level of an atom.
Single bonds are represented by a pair of dots or one line between atoms.
Double bonds are represented by two pairs of dots or two lines between atoms.
Triple bonds are represented by three pairs of dots or three lines between atoms.
ACS Lesson 4.6:

24. 5.1 -What is a Polar Molecule?
The water molecule, as a whole, has 10 protons and 10 electrons, so it is neutral.
In a water molecule, the oxygen atom and hydrogen atoms share electrons in covalent bonds, but the sharing is not equal.
In the covalent bond between oxygen and hydrogen, the oxygen atom attracts electrons a bit more strongly than the hydrogen atoms.
The unequal sharing of electrons gives the water molecule a slight negative charge near its oxygen atom and a slight positive charge near its hydrogen atoms.
When a neutral molecule has a positive area at one end and a negative area at the other, it is a polar molecule.
Water molecules attract one another based on the attraction between the positive end of one water molecule and the negative end of another.
ACS Lesson 5.1:

25. 5.2 -Surface Tension
The attraction of molecules at the surface of a liquid is called surface tension.
The polarity of water molecules can help explain why water has a strong surface tension.
ACS Lesson 5.2:

26. 5.3 - Why Does Water Dissolve in Salt?
The polarity of water molecules enables water to dissolve many ionically bonded substances.
Salt (sodium chloride) is made from positive sodium ions bonded to negative chloride ions.
Water can dissolve salt because the positive part of water molecules attracts the negative chloride ions and the negative part of water molecules attracts the positive sodium ions.
The amount of a substance that can dissolve in a liquid (at a particular temperature) is called the solubility of the substance.
The substance being dissolved is called the solute, and the substance doing the dissolving is called the solvent.
ACS Lesson 5.3:

27. 5.4 -Why Does Water Dissolve in Sugar?
For a liquid to dissolve a solid, the molecules of the liquid and solid must attract one another.
The bond between the oxygen and hydrogen atoms (O–H bond) in sugar (sucrose) gives the oxygen a slight negative charge and the hydrogen a slight positive charge. Sucrose is a polar molecule.
The polar water molecules attract the negative and positive areas on the polar sucrose molecules which makes sucrose dissolve in water.
A nonpolar substance like mineral oil does not dissolve a polar substance like sucrose.
ACS Lesson 5.4:

28. 5.5 - Using Dissolving to Identify an Unknown
Different substances are made from different atoms, ions, or molecules, which interact with water in different ways.
Since dissolving depends on the interaction between water and the substance being dissolved, each substance has a characteristic solubility.
ACS Lesson 5.5:

29. 5.6 - Does Temperature Effect Dissolving?
Adding energy (heating) increases molecular motion.
Increased molecular motion competes with the attraction between solute molecules and tends to make them come apart more easily.
Increased molecular motion causes more solvent molecules to contact solute molecules and pull on them with more force, usually resulting in more dissolving.
Since different substances are made from different atoms, ions, or molecules, increased temperature will affect their dissolving to different extents.
ACS Lesson 5.6:

30. 5.7 - Can Liquids Dissolve in Water?
Liquids have characteristic properties based on the molecules they are made of.
The properties of liquids depend on the attractions the molecules of the liquid have for each other and for other substances.
Liquids can dissolve certain other liquids, depending on the attractions between the molecules of both liquids.
Polar liquids, like water, dissolve other liquids which are polar or somewhat polar.
Polar liquids, like water, do not dissolve nonpolar liquids like oil.
ACS Lesson 5.7:

31. 5.8 -Can Gasses Dissolve in Water?
Gases can dissolve in water.
The dissolving of a gas in water depends on the interaction between the molecules of the gas and the water molecules.
The amount of gas that can be dissolved in water depends on the temperature of the water.
More gas can dissolve in cold water than in hot water.
ACS Lesson 5.8:

32. 5.9 - Temperature Changes in Dissolving
The process of dissolving can be endothermic (temperature goes down) or exothermic (temperature goes up).
When water dissolves a substance, the water molecules attract and “bond” to the particles (molecules or ions) of the substance causing the particles to separate from each other.
The “bond” that a water molecule makes is not a covalent or ionic bond. It is a strong attraction caused by water’s polarity.
It takes energy to break the bonds between the molecules or ions of the solute.
Energy is released when water molecules bond to the solute molecules or ions.
If it takes more energy to separate the particles of the solute than is released when the water molecules bond to the particles, then the temperature goes down (endothermic).
If it takes less energy to separate the particles of the solute than is released when the water molecules bond to the particles, then the temperature goes up (exothermic).
ACS Lesson 5.9:

33. 6.1 - What is a Chemical Reaction?
A physical change, such as a state change or dissolving, does not create a new substance, but a chemical change does.
In a chemical reaction, the atoms and molecules that interact with each other are called reactants.
In a chemical reaction, the atoms and molecules produced by the reaction are called products.
In a chemical reaction, only the atoms present in the reactants can end up in the products. No new atoms are created, and no atoms are destroyed.
In a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.
ACS Lesson 6.1:

34. 6.2 - Controlling the Amount of Products in a Chemical Reaction
Changing the amount of reactants affects the amount of products produced in a chemical reaction.
In a chemical reaction, only the atoms present in the reactants can end up in the products.
Mass is conserved in a chemical reaction.
ACS Lesson 6.2:

35. 6.3 -Forming a Precipitate
The ions or molecules in two solutions can react to form a solid.
A solid formed from two solutions is called a precipitate.
ACS Lesson 6.3:

36. 6.4 -Temperature and Rate of Chemical Reactions
Reactants must be moving fast enough and hit each other hard enough for a chemical reaction to take place.
Increasing the temperature increases the average speed of the reactant molecules.
As more molecules move faster, the number of molecules moving fast enough to react increases, which results in faster formation of products.
ACS Lesson 6.4:

37. 6.5 -A Catalyst and the Rate of Reactions
A catalyst is a substance that can help the reactants in a chemical reaction react with each other faster.
A catalyst does not actually become part of the products of the reaction.
ACS Lesson 6.5:

38. 6.6 - Using Chemical Change to Identify an Unknown
Substances react chemically in characteristic ways
A set of reactions can be used to identify an unknown substance.
Endothermic Reaction
Exothermic Reaction
ACS Lesson 6.6:

39. 6.7 - Energy Changes in Chemical Reactions
If two substances react and the temperature of the mixture decreases, the reaction is endothermic.
If two substances react and the temperature of the mixture increases, the reaction is exothermic.
A chemical reaction involves the breaking of bonds in the reactants and the forming of bonds in the products.
It takes energy to break bonds.
Energy is released when bonds are formed.
If a reaction is endothermic, it takes more energy to break the bonds of the reactants than is released when the bonds of the products are formed.
If a reaction is exothermic, more energy is released when the bonds of the products are formed than it takes to break the bonds of the reactants.
ACS Lesson 6.7:

40. 6.8 - pH and Color Change
Whether a solution is acidic or basic can be measured on the pH scale.
When universal indicator is added to a solution, the color change can indicate the approximate pH of the solution.
Acids cause universal indicator solution to change from green toward red.
Bases cause universal indicator to change from green toward purple.
Water molecules (H2O) can interact with one another to form H3O+ ions and OH− ions.
At a pH of 7, there are equal numbers of H3O+ ions and OH− ions in water, and this is called a neutral solution.
Acidic solutions have a pH below 7 on the pH scale.
Basic solutions have a pH above 7 on the pH scale.
Acids Donate Protons
Bases Accept Protons
ACS Lesson 6.8:

41. 6.9 -Neutralizing Acids and Bases
pH is a measure of the concentration of H3O+ ions in a solution.
Adding an acid increases the concentration of H3O+ ions in the solution.
Adding a base decreases the concentration of H3O+ ions in the solution.
An acid and a base are like chemical opposites.
If a base is added to an acidic solution, the solution becomes less acidic and moves toward the middle of the pH scale. This is called neutralizing the acid.
If an acid is added to a basic solution, the solution becomes less basic and moves toward the middle of the pH scale. This is called neutralizing the base.
Neutralizing an Acidic Solution
ACS Lesson 6.9:

42. 6.10 - Carbon Dioxide Can Make A Solution Acidic
Carbon dioxide (CO2) gas dissolved in water can cause water to become acidic.
The acidity of water from dissolved CO2 can be reduced by a base such as baking soda (sodium bicarbonate).
ACS Lesson 6.10:

43. 6.11 - Chemical Reaction and Engineering
The goal of engineering is to design an object or process to solve a problem.
To design a solution to a problem, engineers need to define the features that will make the object or process successful (criteria) and those that may interfere with the success (constraints).
Engineering involves designing and testing a model/prototype and modifying, improving, and optimizing the prototype based on testing.
Designing a device that uses a chemical reaction to reach a certain temperature range requires testing, measuring, and refining the quantities of substances and modifying the materials for an optimal design.
ACS Lesson 6.11:

44. 6.12 -Synthetic Material and Natural Resources
Synthetic materials are made from natural resources.
Synthetic materials are made by chemically changing the starting substances to create a material with different characteristics.
Some examples of synthetic materials are plastics, medicines, and new fuels.
A synthetic substance may be chemically identical to a naturally-occurring substance or may be different.
Making and using synthetic materials have both positive and negative impacts on society.
ACS Lesson 6.12: