Ch. 7 Foundations of Chemistry
Classifying Matter Matter is anything that has mass and takes up space. Atom - smallest particle of matter 2 Main Classifications of Matter Substance Mixtures
Substances A substance is matter with a composition that is always the same. 2 Types of substances Elements - substances that consist of just one kind of atom Compounds - substances that contain atoms of 2 or more elements chemically bonded together
Compound The symbols and numbers that represents a compound is called a chemical formula. CO 2 The elements that make up the compound is carbon, and oxygen. There are 2 oxygen atoms for every carbon atom. 2 is called the subscript
Properties of Compounds A compound has different physical properties from the individual elements that compose it. Example CO 2 H 2 O CH 4 C 6 H 12 O 6
Mixtures - matter that can vary in composition The amounts of the substance can vary in different parts of the mixture and from mixture to mixture. Mixtures vary depending on how the substances are mixed. Heterogeneous mixture - individual substances are not evenly mixed
Homogeneous Mixtures - individual substances are evenly mixed, the particles are not visible Ex. air, apple juice, salt water Also called a solution Solvent - substance present in the largest amount Solute - substance that is dissolved in the solvent
Dissolve - to form a solution by mixing evenly.
Lesson 1 Review Sugar - sucrose - C 12 H 22 O 11 Element, Compound, or Mixture? Milk Element, Compound or Mixture?
Salt Water - Compound, Heterogeneous Mixture, or Homogeneous Mixture? Oil and Vinegar - Compound, Heterogeneous Mixture or Homogeneous Mixture?
Apple Juice -- Compound, Heterogeneous Mixture, or Homogeneous Mixture? What is the difference between a compound and a mixture?
Physical Properties Lesson 2 A physical property is a characteristic of matter that you can observe or measure without changing the identity of the matter. States of Matter -- Solid, Liquid, Gas
Physical Properties Mass - the amount of matter in an object. Vs weight - the pull of gravity on the matter Volume - amount of space something takes up milliliter (ml) These 2 properties are size dependent, the measurement depends on how large your sample is.
Melting Point - the temperature at which a substance changes from a solid to a liquid. Boiling Point - the temperature at which a substance changes from a liquid to a gas.
Density - the amount of mass per unit of volume Conductivity - the ability of matter to conduct, or carry along electricity or heat
Solubility - the ability of one substance to dissolve in another Magnetism - attractive force for some metals, especially iron
Separating Mixtures Properties of individual substances in a mixture do not change after they are mixed. Parts of a mixture can be separated by physical properties. example - boiling salt water, the water evaporates, leaving the salt using a magnet to separate iron from plastic
Lesson 2 Review What is a physical property?
A characteristic of matter that you can observe or measure without changing the identity of the matter.
What determines the physical properties of matter?
the arrangement of atoms
What are the three states of matter?
solid, liquid, gas
What determines the state of matter?
how close the particles are to one another in the matter and how fast they move
How does mass differ from weight?
Mass is the amount of matter in something Weight is the pull of gravity on matter.
What determines if a property is size-dependent?
A property is size-dependent if its value depends on the size of a sample.
What change of state occurs when a substance reaches its melting point? What occurs when it reaches its boiling point?
A substance changes from a solid to a liquid when it reaches its melting point. It changes from a liquid to a gas when it reaches its boiling point
What two properties must you know to determine density?
mass and volume
How does thermal conductivity differ from electrical conductivity?
Thermal conductivity is the ability of a material to conduct thermal energy. Electrical conductivity is the ability of matter to conduct electric current.
Lesson 3 Physical Changes Physical change is a change in size, shape, form, or state of matter in which the matter s identity stays the same. cut an apple pour juice blow up a balloon
Change in State of Matter solid to liquid to gas Thermal energy must be added to or removed from the particles for change to occur
Adding thermal energy - particles move faster and the temperature increases When the particles are moving too fast for the attractive forces holding them together, the solid reaches its melting point. If more heat is added, the particles keep moving faster until they overcome the attractive forces holding them in a liquid.
Sublimation - a solid changing directly into a gas without first becoming a liquid. example : dry ice (frozen carbon dioxide)
Removing Thermal Energy When thermal energy is removed, the particles move slower. Condensation - when a gas becomes a liquid Solid - particles are held tightly together, they can only vibrate
Freezing and melting are reverse processes and occur at the same temperature. Boiling and condensation are reverse processes and occur at the same temperature.
Deposition - changing directly from a gas to a solid. Deposition is the opposite of sublimation
Dissolving Dissolve - to mix evenly did - because the individual identities of the materials not change, it is a physical change. - easy to reverse - boil the water away
Conservation of Mass Particles of matter are the same before a physical change as they are after a physical change. The total mass does not change during a physical change.
Lesson 4 Chemical Properties and Changes A chemical property is a characteristic of matter that can be observed as it changes to a different type of matter. ability to burn ability to rust
Physical and Chemical Properties Wood Log - physical properties that you can observe with your senses : solid, round, heavy, rough has mass, volume, and density Chemical properties :ability to burn, ability to decompose
Chemical Change -- is a change in matter in which the substances that make up the matter change into other substances with new physical and chemical properties.
Signs of a Chemical Change Bubbles, Color change, Energy change, Odor change These signs mean that there might have been a chemical change. The only proof of a chemical change is the formation of a new substance.
Chemical Equations A chemical equation shows the substances before the reaction takes place and the resulting substances after the reaction. Reactants Products Fe + S ----> FeS yields
During both physical and chemical reactions, mass is conserved. Mass must be equal before and after a change. The number of atoms must be equal before and after a reaction
Balancing Chemical Reactions The chemical formula cannot be changed, just the coefficient in front of the formula. CH 4 + O 2 ----> CO 2 + H 2 O CH 4 + 2O 2 ---> CO 2 + 2H 2 O #atoms #atoms C = 1 C = 1 H = 4 H = 2 O = 2 O = 3
N 2 + H 2 ----> NH 3 N first N 2 + H 2 ------> 2NH 3 Then H N 2 + 3H 2 ----->
Rate of Chemical Reactions page 260 1 Higher temperature usually increases rate of reactions 2. Rate of reaction increases if the concentration of one reactant increases Concentration - the amount of substance in a certain volume 3. Increase surface area of a solid reactant