BackMatter & Energy: Foundations of Chemistry
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Matter & Energy
Introduction to Chemistry
Chemistry is the scientific study of matter and the changes it undergoes under various conditions. It seeks to understand the behavior of matter by examining the behavior of atoms and molecules. Chemistry is integral to everyday experiences, from the air we breathe to the food we eat.
Matter: Anything that has mass and occupies space.
Changes: Chemistry explores not just the properties of matter, but also the mechanisms and reasons behind its transformations.
Scientific Definition: "The science that seeks to understand the behavior of matter by studying the behavior of atoms and molecules."
Classification of Matter
Matter can be classified based on its composition and properties. The main categories are pure substances and mixtures.
Pure Substances: Consist of a single type of particle and maintain consistent properties when physically separated into smaller quantities.
Mixtures: Contain two or more types of particles that can be physically separated and have distinct properties.
Type | Description |
|---|---|
Elements | Single particle (atom) type that cannot be separated into different atoms by breaking chemical bonds. |
Compounds | Composed of two or more different elements chemically bonded in set proportions. |
Homogeneous Mixtures | Solutions with uniform composition. |
Heterogeneous Mixtures | Mixtures with separable components and distinct composition. |
Atoms and Molecules
All matter is composed of elements, which are pure substances built from unique types of atoms. Atoms are the smallest particles of an element that retain its characteristics. Atoms of different elements can combine to form compounds, and molecules are groups of two or more atoms chemically bonded together.
Monatomic Elements: Elements whose atoms exist singly (e.g., noble gases).
Diatomic Elements: Elements whose atoms form pairs (e.g., H2, O2, N2).
Molecules: Two or more atoms that are chemically bonded.
Chemical vs. Physical Changes
Matter can undergo chemical or physical changes. Understanding the difference is fundamental in chemistry.
Chemical Change: A chemical reaction forms new products (e.g., combustion, rusting, digestion).
Physical Change: Matter changes form but not chemical identity (e.g., melting, boiling, shredding, chopping).
Energy
Types of Energy
Energy is defined as the ability to do work. It exists in various forms and can be classified as kinetic or potential energy.
Kinetic Energy | Potential Energy |
|---|---|
Translational (motion) | Gravitational (height) |
Thermal (particles) | Chemical (bonds) |
Radiant (light) | Nuclear (atomic nuclei) |
Law of Conservation of Energy
The Law of Conservation of Energy states that in the absence of external work input or output, the energy of a system remains unchanged. Energy cannot be created or destroyed, only transformed from one form to another.
Mechanical Energy: The sum of potential and kinetic energy in a system.
States of Matter (Phases)
Matter exists in different states, determined by the arrangement and motion of its particles. The three primary states are solids, liquids, and gases.
Solids: Particles are closely packed and vibrate in place.
Liquids: Particles are less tightly packed and can move past each other.
Gases: Particles are far apart and move freely.
Particles are always in motion, possessing kinetic energy. The kinetic energy increases from solids to liquids to gases.
Thermal Energy
Thermal energy is the energy associated with the kinetic energy (motion) of particles in a substance. As the temperature increases, the thermal energy of the particles increases.
Temperature
Temperature is a measure of the average kinetic energy of particles in matter. It is commonly measured in degrees Celsius (°C), Fahrenheit (°F), or Kelvin (K).
Temperature Scale | Boiling Point of Water | Human Body Temp | Freezing Point of Water |
|---|---|---|---|
Fahrenheit (°F) | 212 | 98 | 32 |
Celsius (°C) | 100 | 37 | 0 |
Kelvin (K) | 373 | 310 | 273 |
Heat vs. Temperature
Heat is the flow of energy caused by a temperature difference, while temperature is a measure of the average kinetic energy of particles. Heat is measured in joules (J) or calories (cal), and temperature in degrees Celsius, Fahrenheit, or Kelvin.
Energy and Work
Energy is the capacity to do work. Work is the flow of energy caused by force and displacement. The equation for work is:
where F is force and d is displacement.
Energy and Heat
Heat is the flow of energy due to a temperature difference. The units for heat are joules (J) or calories (cal).
Gram calorie (cal): Heat energy needed to raise the temperature of 1 g of water by 1°C ().
Food Calorie (Cal): Nutritional energy content found by burning 1 g of carbohydrate, fat, or protein ().
Specific Heat Capacity
Definition and Calculation
Specific heat capacity (c) is the amount of heat required to raise the temperature of 1 gram of a substance by 1°C. Different substances have different specific heat capacities.
Substance | Specific Heat Capacity (J/g°C) |
|---|---|
Copper | 0.385 |
Water | 4.184 |
The heat (q) lost or gained by a substance can be calculated using:
where m is mass, c is specific heat capacity, and is the temperature change.
Example Calculation
Therapeutic hypothermia is used to treat patients after cardiac arrest. To calculate the heat lost when cooling a patient's blood volume from 38.5°C to 33.2°C (assuming blood has the same specific heat as water):
where m = 5500 g, c = 4.184 J/g°C, = (33.2 - 38.5)°C.
Changes of State
Phase Changes
Matter changes state through the addition or removal of energy. The main phase changes are melting, freezing, vaporization, condensation, and sublimation.
Melting: Solid to liquid
Freezing: Liquid to solid
Vaporization: Liquid to gas
Condensation: Gas to liquid
Sublimation: Solid to gas
During a change of state, energy is used to break the attractions between molecules, and temperature remains constant until the process is complete.
Applied Chemistry: Calculations and Examples
Energy Values of Food Types
Food Type | kcal/g | kJ/g |
|---|---|---|
Carbohydrate | 4 | 17 |
Fat | 9 | 38 |
Protein | 4 | 17 |
Example: Calculating kilocalories from IV glucose solution using concentration and volume.
Body Temperature and Heat Transfer
Example: Calculating if 100 kJ of heat is enough to raise the body temperature of a 55 kg person from 13.7°C to normal, using the specific heat capacity of human tissue (3.5 J/g°C).
Infusion Time Calculation
Example: Calculating the time to deliver 500 mL of IV saline at a rate of 80 mL/h.
Body Fat Calculation
Example: Determining the weight of fat in pounds for a 74-kg athlete with 15% body fat.
Medication Dosage Calculation
Example: Calculating the volume of Medrol to administer based on body weight and concentration.
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