Unit 2: Matter and Energy Sections 1.2, 1.4, Chapter 3, and Sections 15.1-15.2

Matter’s Properties and Changes Sections 3.1 and 3.2

Physical Properties Describe the look/feel/smell/taste of a substance Extensive physical properties depend on how much matter is present Mass Length Volume Width Shape

Physical Properties Intensive physical properties don’t depend on how much matter is present Density Malleability Boiling point Melting point Color Conductivity Luster Odor

Chemical Properties Describe how a substance reacts with another substance Example Paper is flammable Lab bench is not

Physical Change No new substance is formed The change can be easily reversed Ex: Ice melts (change of state) Spoon is bent (change of shape) CO2 gas is dissolved in H2O

Chemical Change A new substance is formed The change cannot be easily reversed – if at all Ex: Paper burns O2 reacts with Fe to create rust (Fe2O3) Rule of Thumb – a chemical change has occurred if a… new solid or gas forms permanent color/energy change occurs

How can a chemical change result in a change in a physical property? When something new is formed its physical properties are likely different than those of the original substance

Classification of Matter Sections 3.3 and 3.4

Classification of Matter Two major categories: Pure substances – including elements and compounds Mixtures – including homogeneous and heterogeneous mixtures

Cannot be separated by physical means Pure substances Cannot be separated by physical means Filtration Evaporation Chromatography Elements in a compound could be separated, but only w/a chemical reaction

Elements One kind of atom Ex: C (carbon) O2 (oxygen)

Compounds More than one kind of atom Atoms chemically combined (bonded) Ex: CO2 (carbon dioxide)

Homogeneous mixtures You cannot see the different parts Ex: Air Alcohol mixed w/ water NaCl dissolved in water A.K.A. solutions

Heterogeneous mixtures Includes suspensions and colloids You can see the different parts Ex: Italian salad dressing Granite Milk

Summarizer: Matter

Energy and Conservation Laws Section 15.1

Types of Energy Potential – energy due to particle arrangement (or position) Kinetic – energy due to motion Radiant – energy in the form of electromagnetic waves (A.K.A. light)

Energy Units Joule – SI unit for energy calorie – Imperial unit for energy 1 calorie = 4.184 joules 1 kilocalorie (kcal) = 1000 calories (cal)

Law of Conservation of Mass Matter is never created or destroyed in the universe It may change state or leave a system, but the total mass of the universe is constant

Open vs. Closed Systems Open: Interacts w/surroundings Matter and energy can pass in and out Ex: uncovered pot boiling on the stove Closed: Opposite of open! Ex: thermos

Law of Conservation of Energy Energy is never created or destroyed in the universe It may convert into another type of energy or leave a system, but the total energy in the universe is constant

Endothermic vs. Exothermic Processes Requires energy absorption as heat Ex: ice melting Exothermic Releases energy as heat Ex: gasoline combustion

Activation energy Energy needed to start a reaction Exothermic – products have a lower potential energy

Law of Conservation of Mass-energy Sum total amount of mass and energy in the universe is constant Mass may change into energy and vice-versa Applies to nuclear reactions

Heat and Temperature Sections 15.1 and 15.2

Thermal energy vs. Heat Thermal energy: kinetic energy of the particles in a substance Heat: thermal energy moving from a hot substance to a cold one Could also use the phrase “heat transfer”

Heat vs. temperature Temp: measure of average kinetic energy of the particles in a substance A.K.A average thermal energy Changes during heat transfer

Specific Heat Amount of heat needed to raise the temp of an object Heat = thermal energy transferred into the object

It is May 1 and we are experiencing an extremely hot spring day It is May 1 and we are experiencing an extremely hot spring day. The air is about 87 0 F. You decide to go swimming in Lake Pearl. How will the water temperature feel? How does the specific heat of water compare to the specific heat of air? Water temp will feel cold because water has a higher specific heat than air  takes more energy to increase temp