Knowt
Building Blocks for Understanding
Basic Concepts and Units of Measurement
1. Scientific Units and Measurements
SI Units: The International System of Units (SI) is the standard system of measurement used in science.
Length: Meter (m)
Mass: Kilogram (kg)
Time: Second (s)
Temperature: Kelvin (K) or Celsius (°C)
Amount of Substance: Mole (mol)
Example: Measuring the length of a table in meters.
2. Prefixes and Conversions
Common Prefixes:
Kilo- (k): 10³
Centi- (c): 10−²
Milli- (m): 10−³
Micro- (μ): 10−⁶
Nano- (n): 10−⁹
Example: Converting 1 kilometer to meters (1 km = 1000 m).
3. Accuracy and Precision
Accuracy: How close a measured value is to the true value.
Example: Measuring the boiling point of water to be 100.0°C.
Precision: How close repeated measurements are to each other.
Example: Repeated measurements of a length giving values of 10.2 cm, 10.3 cm, and 10.1 cm.
The Structure of Atoms
1. Atomic Structure
Subatomic Particles: Atoms are made up of protons, neutrons, and electrons.
Protons: Positively charged particles in the nucleus.
Neutrons: Neutral particles in the nucleus.
Electrons: Negatively charged particles orbiting the nucleus.
Example: The hydrogen atom has 1 proton and 1 electron.
2. Atomic Number and Mass Number
Atomic Number (Z): The number of protons in an atom.
Example: Carbon has an atomic number of 6.
Mass Number (A): The total number of protons and neutrons in an atom.
Example: Carbon-12 has 6 protons and 6 neutrons, so its mass number is 12.
3. Isotopes
Definition: Atoms of the same element with different numbers of neutrons.
Example: Carbon-12, Carbon-13, and Carbon-14 are isotopes of carbon.
4. Electron Configuration
Shells and Energy Levels: Electrons occupy energy levels or shells around the nucleus.
First Shell: Can hold up to 2 electrons.
Second Shell: Can hold up to 8 electrons.
Example: The electron configuration of oxygen is 2, 6.
Elements, Compounds, and Mixtures
1. Elements
Definition: Pure substances consisting of only one type of atom.
Example: Oxygen (O), Hydrogen (H), and Carbon (C).
2. Compounds
Definition: Substances formed from two or more elements chemically bonded together.
Types of Chemical Bonds:
Ionic Bonds: Transfer of electrons from one atom to another.
Covalent Bonds: Sharing of electrons between atoms.
Example: Water (H₂O), formed from hydrogen and oxygen atoms.
3. Mixtures
Definition: A combination of two or more substances that are not chemically bonded.
Homogeneous Mixtures: Uniform composition throughout.
Heterogeneous Mixtures: Non-uniform composition.
Example: Saltwater is a homogeneous mixture, while a salad is a heterogeneous mixture.
Chemical Reactions
1. Types of Chemical Reactions
Synthesis Reaction: Two or more simple substances combine to form a more complex substance.
Example: 2H₂ + O₂ → 2H₂O
Decomposition Reaction: A complex substance breaks down into simpler substances.
Example: 2H₂O → 2H₂ + O₂
Single Replacement Reaction: One element replaces another in a compound.
Example: Zn + 2HCl → ZnCl₂ + H₂
Double Replacement Reaction: Exchange of ions between two compounds.
Example: AgNO₃ + NaCl → AgCl + NaNO₃
2. Balancing Chemical Equations
Law of Conservation of Mass: Mass is neither created nor destroyed in a chemical reaction.
Example: Balancing CH₄ + 2O₂ → CO₂ + 2H₂O
3. Energy Changes in Reactions
Exothermic Reactions: Release energy, usually in the form of heat.
Example: Combustion of methane.
Endothermic Reactions: Absorb energy.
Example: Photosynthesis in plants.
Biological Macromolecules
1. Carbohydrates
Definition: Organic compounds made up of carbon, hydrogen, and oxygen.
Monosaccharides: Simple sugars (e.g., glucose).
Disaccharides: Two monosaccharides bonded together (e.g., sucrose).
Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose).
Example: Glucose (C₆H₁₂O₆) is a common monosaccharide used by cells for energy.
2. Proteins
Structure: Composed of amino acids linked by peptide bonds.
Functions: Enzymes, structural components, transport molecules, antibodies.
Example: Hemoglobin, the protein in red blood cells that carries oxygen.
3. Lipids
Structure: Made up of glycerol and fatty acids.
Functions: Energy storage, insulation, and making up cell membranes.
Example: Triglycerides, phospholipids in cell membranes.
4. Nucleic Acids
Structure: Made up of nucleotides.
Types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
Functions: Store and transmit genetic information.
Example: DNA carries the genetic blueprint of an organism.
The Cell as the Basic Unit of Life
1. Cell Theory
Principles:
All living organisms are composed of one or more cells.
The cell is the basic unit of life.
All cells arise from pre-existing cells.
Example: Unicellular organisms like bacteria consist of a single cell.
2. Prokaryotic and Eukaryotic Cells
Prokaryotic Cells: Simple, lack a nucleus.
Example: Bacteria.
Eukaryotic Cells: Complex, with a nucleus and membrane-bound organelles.
Example: Plant and animal cells.
3. Cell Organelles
Nucleus: Contains genetic material (DNA).
Example: Control center of the cell.
Mitochondria: Powerhouse of the cell, produces energy (ATP).
Example: Site of cellular respiration.
Ribosomes: Synthesize proteins.
Example: Found in the cytoplasm or on the endoplasmic reticulum.
Chloroplasts: Site of photosynthesis in plant cells.
Example: Contain chlorophyll, which captures light energy.
Cell Membrane: Regulates what enters and exits the cell.
Example: Composed of a phospholipid bilayer.
4. Cellular Processes
Photosynthesis: Conversion of light energy into chemical energy in plants.
Equation: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂
Example: Plants use sunlight to produce glucose.
Cellular Respiration: Process of breaking down glucose to produce ATP.
Equation:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
Example: Cells use glucose and oxygen to produce energy.
Building Blocks for Understanding
Basic Concepts and Units of Measurement
1. Scientific Units and Measurements
SI Units: The International System of Units (SI) is the standard system of measurement used in science.
Length: Meter (m)
Mass: Kilogram (kg)
Time: Second (s)
Temperature: Kelvin (K) or Celsius (°C)
Amount of Substance: Mole (mol)
Example: Measuring the length of a table in meters.
2. Prefixes and Conversions
Common Prefixes:
Kilo- (k): 10³
Centi- (c): 10−²
Milli- (m): 10−³
Micro- (μ): 10−⁶
Nano- (n): 10−⁹
Example: Converting 1 kilometer to meters (1 km = 1000 m).
3. Accuracy and Precision
Accuracy: How close a measured value is to the true value.
Example: Measuring the boiling point of water to be 100.0°C.
Precision: How close repeated measurements are to each other.
Example: Repeated measurements of a length giving values of 10.2 cm, 10.3 cm, and 10.1 cm.
The Structure of Atoms
1. Atomic Structure
Subatomic Particles: Atoms are made up of protons, neutrons, and electrons.
Protons: Positively charged particles in the nucleus.
Neutrons: Neutral particles in the nucleus.
Electrons: Negatively charged particles orbiting the nucleus.
Example: The hydrogen atom has 1 proton and 1 electron.
2. Atomic Number and Mass Number
Atomic Number (Z): The number of protons in an atom.
Example: Carbon has an atomic number of 6.
Mass Number (A): The total number of protons and neutrons in an atom.
Example: Carbon-12 has 6 protons and 6 neutrons, so its mass number is 12.
3. Isotopes
Definition: Atoms of the same element with different numbers of neutrons.
Example: Carbon-12, Carbon-13, and Carbon-14 are isotopes of carbon.
4. Electron Configuration
Shells and Energy Levels: Electrons occupy energy levels or shells around the nucleus.
First Shell: Can hold up to 2 electrons.
Second Shell: Can hold up to 8 electrons.
Example: The electron configuration of oxygen is 2, 6.
Elements, Compounds, and Mixtures
1. Elements
Definition: Pure substances consisting of only one type of atom.
Example: Oxygen (O), Hydrogen (H), and Carbon (C).
2. Compounds
Definition: Substances formed from two or more elements chemically bonded together.
Types of Chemical Bonds:
Ionic Bonds: Transfer of electrons from one atom to another.
Covalent Bonds: Sharing of electrons between atoms.
Example: Water (H₂O), formed from hydrogen and oxygen atoms.
3. Mixtures
Definition: A combination of two or more substances that are not chemically bonded.
Homogeneous Mixtures: Uniform composition throughout.
Heterogeneous Mixtures: Non-uniform composition.
Example: Saltwater is a homogeneous mixture, while a salad is a heterogeneous mixture.
Chemical Reactions
1. Types of Chemical Reactions
Synthesis Reaction: Two or more simple substances combine to form a more complex substance.
Example: 2H₂ + O₂ → 2H₂O
Decomposition Reaction: A complex substance breaks down into simpler substances.
Example: 2H₂O → 2H₂ + O₂
Single Replacement Reaction: One element replaces another in a compound.
Example: Zn + 2HCl → ZnCl₂ + H₂
Double Replacement Reaction: Exchange of ions between two compounds.
Example: AgNO₃ + NaCl → AgCl + NaNO₃
2. Balancing Chemical Equations
Law of Conservation of Mass: Mass is neither created nor destroyed in a chemical reaction.
Example: Balancing CH₄ + 2O₂ → CO₂ + 2H₂O
3. Energy Changes in Reactions
Exothermic Reactions: Release energy, usually in the form of heat.
Example: Combustion of methane.
Endothermic Reactions: Absorb energy.
Example: Photosynthesis in plants.
Biological Macromolecules
1. Carbohydrates
Definition: Organic compounds made up of carbon, hydrogen, and oxygen.
Monosaccharides: Simple sugars (e.g., glucose).
Disaccharides: Two monosaccharides bonded together (e.g., sucrose).
Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose).
Example: Glucose (C₆H₁₂O₆) is a common monosaccharide used by cells for energy.
2. Proteins
Structure: Composed of amino acids linked by peptide bonds.
Functions: Enzymes, structural components, transport molecules, antibodies.
Example: Hemoglobin, the protein in red blood cells that carries oxygen.
3. Lipids
Structure: Made up of glycerol and fatty acids.
Functions: Energy storage, insulation, and making up cell membranes.
Example: Triglycerides, phospholipids in cell membranes.
4. Nucleic Acids
Structure: Made up of nucleotides.
Types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
Functions: Store and transmit genetic information.
Example: DNA carries the genetic blueprint of an organism.
The Cell as the Basic Unit of Life
1. Cell Theory
Principles:
All living organisms are composed of one or more cells.
The cell is the basic unit of life.
All cells arise from pre-existing cells.
Example: Unicellular organisms like bacteria consist of a single cell.
2. Prokaryotic and Eukaryotic Cells
Prokaryotic Cells: Simple, lack a nucleus.
Example: Bacteria.
Eukaryotic Cells: Complex, with a nucleus and membrane-bound organelles.
Example: Plant and animal cells.
3. Cell Organelles
Nucleus: Contains genetic material (DNA).
Example: Control center of the cell.
Mitochondria: Powerhouse of the cell, produces energy (ATP).
Example: Site of cellular respiration.
Ribosomes: Synthesize proteins.
Example: Found in the cytoplasm or on the endoplasmic reticulum.
Chloroplasts: Site of photosynthesis in plant cells.
Example: Contain chlorophyll, which captures light energy.
Cell Membrane: Regulates what enters and exits the cell.
Example: Composed of a phospholipid bilayer.
4. Cellular Processes
Photosynthesis: Conversion of light energy into chemical energy in plants.
Equation: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂
Example: Plants use sunlight to produce glucose.
Cellular Respiration: Process of breaking down glucose to produce ATP.
Equation:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
Example: Cells use glucose and oxygen to produce energy.
