Science E Assessment: Matter and Its Forms

Matter

• Matter is anything that has mass and takes up space.
• It includes everything around us, from air to solids and liquids.

Differences between Elements, Molecules, Compounds, and Mixtures

• Elements: Pure substances consisting of only one type of atom (e.g., Oxygen, O₂).
• Molecules: Two or more atoms bonded together, which can be the same or different elements (e.g., O₂, H₂O).
• Compounds: Substances made up of two or more different elements chemically bonded together (e.g., Water, H₂O).
• Mixtures: A combination of two or more substances that are not chemically bonded (e.g., salt water).

Bonding

• Ionic Bonding: Occurs when electrons are transferred from one atom to another, resulting in the formation of ions (e.g., NaCl).
• Covalent Bonding: Occurs when atoms share electrons to achieve a full outer shell (e.g., H₂O).

Writing and Naming Ionic Compounds

• Write the symbol of the cation (positive ion) and the anion (negative ion).
• Balance the charges to ensure the compound is neutral.
• Name the cation first, followed by the anion with an "-ide" suffix (e.g., NaCl is sodium chloride).

Characteristics of Living Things

• Living things:
  • Are made of cells
  • Grow and develop
  • Reproduce
  • Respond to stimuli
  • Obtain and use energy
  • Maintain homeostasis
  • Evolve over time

Importance of Protein

• Proteins are essential for:
  • Building and repairing tissues
  • Enzymatic activities
  • Transporting molecules
  • Immune responses

Central Dogma

• The central dogma of molecular biology describes the flow of genetic information: DNA → RNA → Protein.

Transcription and Translation

• Transcription: The process by which a segment of DNA is copied into RNA by the enzyme RNA polymerase.
• Translation: The process by which the sequence of an mRNA molecule is used to produce a corresponding protein.

Reactions

• Types of Reactions:
  • Combination: Two or more substances combine to form one product (e.g., A + B → AB).
  • Decomposition: A single compound breaks down into two or more products (e.g., AB → A + B).
  • Single Displacement: One element replaces another in a compound (e.g., A + BC → AC + B).
  • Double Displacement: Exchange of ions between two compounds (e.g., AB + CD → AD + CB).
  • Combustion: A substance reacts with oxygen, releasing energy in the form of light and heat (e.g., CH₄ + 2O₂ → CO₂ + 2H₂O).

Writing Chemical Reactions

• Write the reactants on the left side, products on the right side, and balance the equation.
• Balance the equation by adjusting the coefficients to ensure the same number of atoms of each element on both sides of the equation.

Hierarchy of Life / Organization

• Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere

Moles

• Determining the Molar Mass of a Compound:
  • Add the atomic masses of all the atoms in the compound (e.g., H₂O = 2(1) + 16 = 18 g/mol).
• Calculations between Moles, Particles, and Avogadro’s Number:
  • 1 mole = 6.022 × 10²³ particles (atoms, molecules).
• Calculations between Moles, Mass, and Molar Mass:
  • Moles = Mass / Molar Mass.
• Using Mole Ratios from Chemical Equations to Determine the Amount of Product Being Made:
  • Use the coefficients in the balanced equation to find the ratio of reactants to products.
• Calculating the Limiting Reactant:
  • Determine which reactant produces the least amount of product, as it limits the reaction.

Viruses

• Characteristics (Living/Nonliving):
  • Viruses are considered nonliving because they cannot reproduce or carry out metabolic processes without a host cell.
• Structure:
  • Capsid: Protein shell
  • Genetic Material: DNA or RNA
  • Envelope: Some have a lipid envelope
• Life Cycle of Viruses:
  • Attachment
  • Entry
  • Replication
  • Assembly
  • Release

Endothermic and Exothermic Reactions

• Define:
  • Endothermic: Absorbs heat from surroundings (e.g., melting ice).
  • Exothermic: Releases heat to surroundings (e.g., combustion).
• Identify Features from Energy Profile Graphs:
  • Endothermic: Products have higher energy than reactants.
  • Exothermic: Products have lower energy than reactants.