Understanding Energy and Temperature: Key Concepts in Physical and Chemical Changes
Energy plays a vital role in physical and chemical changes. It is defined as the ability to transfer heat or perform work, with various sources including chemical, nuclear, kinetic, electrical, and gravitational energy. Heat, a form of energy measured in joules, differs from temperature, which quantifies how hot or cold something is in degrees Celsius or Kelvin. This guide explores the nature of temperature, the movement of atoms when heated, phase changes, and the Law of Conservation of Energy, providing essential insights into fundamental chemistry concepts.
Understanding Energy and Temperature: Key Concepts in Physical and Chemical Changes
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Presentation Transcript
F. Energy is always involved in physical and chemical change Energy definition: ability to transfer heat or do work Examples of energy sources Chemical Nuclear Kinetic Electrical Gravity (or positional)
Heat and temperature are different • Key concept in chemistry • Heat is a form of energy (measured in joules) • Temperature is a measure of hotness or coldness (measured in ºC or K) • Actually the average kinetic energy of the atoms When a scientist heats a substance, she is adding ___________. This results in the atoms in the substance moving ___________ and so the temperature increases.
What about Temperature? We all know that some things feel hot, and others cold, but is there more to temperature than that? When an object feels hot, the atoms inside it are moving fast in random directions, and when it feels cold, they are moving slowly. Our body interprets that random atomic motion into what we feel as hot and cold, and a thermometer interprets that atomic motion as a certain number of degrees. So when I'm heating something, I'm just making its atoms move faster? Exactly. If the object is a solid the atoms are vibrating back and forth, and if it is a gas like the air, the atoms are flying around much like little balls.
Energy, usually in the form of heat, is involved in changes of state (phase changes.) Heat is __________________. Therefore, it is a _______________ change. Phase change Phase change Solid Heat is __________________. Therefore, it is a _______________ change.
F. Energy is always involved in physical and chemical change 1. Exothermic: We use the words: 2. Endothermic We use the words:
The Law of Conservation of Energy • Energy is neither _______________ nor ______________ in a chemical reaction.
Formative Assessment • I use the results to help plan lessons for this class • Do you best • Full credit for trying
Graphing a heating curve • Graphs in chemistry & science • Title • Label each axis • X axis = independent variable (scientist controls) • Y axis = dependent variable (resulting values due to the changes in the independent variable) • Units must always be given • Line graphs are the most common for experimental data Heating curve worksheet: X axis = Time Y axis = Temperature
Animation – heating curve • http://www.dlt.ncssm.edu/tiger/Flash/phase/HeatingCurve.html • http://www.chm.davidson.edu/vce/phasechanges/HeatingCurve.html • http://www.kentchemistry.com/links/Matter/HeatingCurve.htm • Tutorial
Using reference tables in chemistry • Scientists must be able to interpret and use reference tables. • This provides information about a substance without the scientist having to make the measurements.
T E M P E R A T U R E V IV III II I TIME Heating Curve
