Ch 2 Matter and Energy Sec 1 Energy Sec 2 Studying Matter and Energy Sec 3 Measurements and Calc in Chem

Sec. 1 Energy I can Explain that physical and chemical changes involve transfer of energy I can apply the law of conservation of energy to analyze changes in matter I can distinguish between heat and temperature I can convert between the Celsius and Kelvin Temp. scales

Energy and Change Energy is the capacity to do work(example: form a new compound)

Energy and Change Changes in matter can be physical or chemical A physical change only affects the physical properties of a substance (Ice melting, Water Boiling) A chemical change occurs whenever a new substance is formed. (H and O react to produce water)

Energy and Change Every change of matter involves a chemical change In some changes energy must be applied In other cases energy is released

Energy and Change Endothermic processes are processes in which heat is absorbed from the surrounding (ex: ice melting and water boiling) Exothermic processes are processes in which heat is released into the surrounding (the freezing of water and the condensation of water vapor)

Energy and Change Law of conservation of energy states that energy can not be created or destroyed Energy can be transfered

Heat Heat is energy transferred between objects that are at different temperatures. Heat is always transferred from the warmer object to the cooler object Energy released as heat is an exothermic reaction(grandcamp) Baking a cake is an endothermic reaction(baking soda)

Heat The transfer of energy as heat can be measured by calculating the change in temp. Temp is the measure of the avg. KE of particles

Temp Scales Converting from C to K T(C)= T(K) – 273 T(k)= T(C) + 273

Sec 2 Studying Matter I can Describe how chemists use the scientific method I can explain the purpose of controlling the conditions of an experiment I can explain the difference between hypothesis, a theory, and a law

Scientific Method

Scientific method Experiments may not always turn out as expected, this results can be just as important as finding unexpected results. Teflon Synthetic dyes Pennicilin http://science.discovery.com/brink/top-ten/accidental-inventions/inventions-01.html

Scientific Explanations Chemists use experiments to test a hypothesis In experiments there are variables that can change and affect an experiment. We try to reduce the amount of variables in an experiment and increase the amount of controls

Theory vs Law Theories an explanation for a phenomenon that is based on observation, experimentation, and reasoning A Law is a summary of many experimental results and observations

Scientific Models Models are used to take something microscopic and enlarge it to get a better understanding of how it works.

Sec. 3 Measurements and Calculations in Chemistry It is important to select the right piece of equipment to make measurements with. Accuracy is how close a measurement is to its true value. Precision is how closely several measurements agree Ex: Darts

Significant Figures Significant figures are made up of all the numbers that are known for certain. Turn to page 57 to see the rules for identifying sig figs

Math and Sig Figs When multiplying or dividing, the answer can not have more sig figs than there are in the measurement with the smallest sig figs. In addition and subtraction, the result can be no more certain than the number in the calculation. If a calculation has both add/sub and mult/div, round after each operation Turn to page 58 and 59

Scientific Notation See page 62