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The Missing Ingredient
The Missing Ingredient
So far we have been neglecting an important reactant/product in our chemical equations.
So far we have been neglecting an important reactant/product in our chemical equations.
What is Energy?
What is Energy?
Energy is the ability to do work. Work can be several things. For example, work could be to move an object, change it's shape, heat it up, etc.
Energy can be in several forms:
All chemicals have chemical energy stored in the bonds between their atoms. They also have thermal (heat) energy. Thermochemistry is the study of heat energy.
Kinetic Molecular Theory
Kinetic Molecular Theory
This theory states that all atoms are moving. Some atoms vibrate in place like solids do. Some move around like liquids and gases.
Temperature is the average kinetic energy in a substance. The faster the atoms or molecules move the higher the kinetic energy and the higher the temperature.
Solids have the lowest energy
Liquids are in the middle
Gases have the highest amount of energy of the three
Temperature scales
Temperature scales
Scientists use 2 common scales of temperature: Celcius and Kelvin.
Celsius is based on the freezing and boiling point of water. 0°C is the freezing point where water turns into ice. 100°C is the boiling point where water turns into steam.
It may not be a surprise that there are things that are colder than water or ice. Kelvin is based on the absolute lowest temperature of matter. At 0 Kelvin (no degree symbol) all atoms stop moving. There is no colder temperature. Even the vacuum of space is not zero it's about 2.7 Kelvin.
Temperature Conversions
Temperature Conversions
Fahrenheit and Celsius can be converted using the formula to the right:
converting between Celsius and Kelvin is easier:
°C = K + 273
K = °C - 273
Is it Hot in Here? or is it just me?
Is it Hot in Here? or is it just me?
Heat is the transfer of thermal energy, so for one object it will feel like it's getting hotter and the other it will feel like it's getting colder. There are always two perspectives.
Endothermic is the perspective of heat entering. (Remember the "EN" in endothermic means entering) The object gains energy. We feel colder because energy is leaving us and entering the object.
Exothermic is the perspective of heat exiting. (Remember the "EX" in exothermic means exiting) The object gets loses energy. We feel hotter because energy is leaving the object and entering us.
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