Elements compounds and mixtures

Q: What is an element?

A: A pure substance made up of only one type of atom.

Q: Give 3 examples of elements that are metals and 3 that are non-metals.

A: Metals: Iron, Copper, Gold. Non-metals: Oxygen, Carbon, Sulfur.

Q: Why can’t an element be broken down into anything simpler by chemical means?

A: Because it only contains one type of atom, the simplest form of matter.

Q: What are the 3 main subatomic particles inside an atom and their charges?

A: Proton (+), Neutron (0), Electron (–).

Q: What is an element?

A: An element is a pure substance that consists of only one type of atom and cannot be broken down into simpler substances by ordinary chemical means. Each element has unique chemical and physical properties.

Q: Give 3 examples of elements that are metals and 3 that are non-metals.

A: Metals: Iron (Fe), Copper (Cu), Gold (Au). These are generally shiny, good conductors of heat and electricity, and malleable. Non-metals: Oxygen (O), Carbon (C), Sulfur (S). These are often dull, poor conductors, and brittle.

Q: Why can’t an element be broken down into anything simpler by chemical means?

A: An element cannot be broken down chemically because it is composed entirely of one type of atom, which represents the most fundamental and simplest stable form of matter. Chemical reactions rearrange atoms but do not change the identity of the atoms themselves.

Q: What are the 3 main subatomic particles inside an atom and their charges?

A: The three main subatomic particles comprising an atom are:

1. Proton: Carries a positive electrical charge (+1).
2. Neutron: Carries no electrical charge (neutral or 0).
3. Electron: Carries a negative electrical charge (-1).

Q: Where are protons, neutrons, and electrons found in an atom?

A: In an atom, protons and neutrons are located together in the nucleus, which is the small, dense central region of the atom. The electrons orbit the nucleus in specific energy levels or regions called electron shells (or energy levels).

Q: Define “atomic number.”

A: The atomic number (Z) is the unique number of protons found in the nucleus of an atom of a specific element. This number defines the identity of an element; for example, all atoms with 6 protons are carbon atoms.

Q: What does the periodic table organise?

A: The periodic table organises all known chemical elements in a structured grid, primarily by increasing atomic number. It systematically arranges them to display recurring trends in their chemical and physical properties, allowing for prediction of behavior.

Q: What is a group vs a period in the periodic table?

A: In the periodic table:

• Groups are the vertical columns. Elements within the same group tend to have similar chemical properties because they have the same number of valence electrons (outermost electrons).
• Periods are the horizontal rows. Elements in the same period have the same number of electron shells (or energy levels) occupied by electrons.

Q: What are 2 properties of metals vs 2 properties of non-metals?

A:

• Metals:

  • Shiny (Lustrous): Reflect light well.
  • Good conductors: Efficiently transfer heat and electricity.
  • Malleable: Can be hammered or pressed into thin sheets without breaking (e.g., Iron, Copper).

• Non-metals:

  • Dull: Do not reflect light well, lacking luster.
  • Brittle: Tend to break or shatter upon impact and are not easily reshaped.
  • Poor conductors: Do not efficiently transfer heat or electricity (they are insulators) (e.g., Sulfur, Carbon).

Q: What is a compound?

A: A compound is a pure substance formed when two or more different elements are chemically combined in fixed proportions. This chemical combination results in a new substance with properties distinct from its constituent elements.

Q: Give an example of a compound and its elements.

A: Common examples of compounds and their constituent elements include:

1. Water (H_2O): Made of hydrogen (H) and oxygen (O), chemically combined in a fixed ratio of two hydrogen atoms to one oxygen atom.
2. Carbon Dioxide (CO_2): Made of carbon (C) and oxygen (O).
3. Sodium Chloride (NaCl): Made of sodium (Na) and chlorine (Cl).

Q: How are compounds different from mixtures?

A: The key difference lies in their bonding:

• Compounds involve a chemical bond between elements, forming a new substance with different properties that are difficult to separate.
• Mixtures involve substances that are only physically combined, not chemically bonded, retaining their original properties and often separable by physical means.

Q: What is the difference between homogeneous and heterogeneous mixtures?

A:

• Homogeneous mixtures have a uniform composition and appearance throughout. Their components are evenly distributed and indistinguishable, like salt dissolved in water.
• Heterogeneous mixtures have a non-uniform composition, with visibly distinct parts or phases. Their components are not evenly distributed, such as a salad or sand and water.

Q: Name 3 methods of separating mixtures with examples.

A:

1. Filtration: Separates insoluble solids from liquids (e.g., separating sand from water by pouring through filter paper).
2. Distillation: Separates liquids with different boiling points or a solid from a liquid in a solution by heating and condensing (e.g., separating alcohol from water).
3. Evaporation: Separates a soluble solid from a liquid in a solution by heating the liquid until it turns into gas, leaving the solid behind (e.g., recovering salt from saltwater).

Q: What is a solution?

A: A solution is a special type of homogeneous mixture where one substance (the solute) is completely and uniformly dissolved into another substance (the solvent). The particles are so small that they are evenly dispersed and do not settle out.

Q: What is the difference between solute and solvent?

A: In a solution:

• The solute is the substance that is dissolved into another substance. It is usually present in a smaller amount (e.g., sugar).
• The solvent is the substance that does the dissolving. It is typically present in the larger amount and creates the medium for dissolution (e.g., water).

Q: How did the scientific method improve chemistry compared to alchemy?

A: The scientific method revolutionized chemistry by introducing a systematic, empirical approach based on observable evidence and experimentation. Unlike alchemy, which relied on mystical beliefs and lacked rigorous testing, the scientific method emphasized:

1. Testable hypotheses: Formulating predictions that can be verified or falsified.
2. Controlled experiments: Designing experiments to isolate variables and ensure reliability.
3. Data analysis and peer review: Objectively interpreting results and subjecting findings to scrutiny, leading to verifiable and cumulative discoveries.

Q: Compare element, compound, and mixture.

A: Here’s a comparison:

• Element: A pure substance consisting of only one type of atom (e.g., Oxygen, Gold).
• Compound: A pure substance formed when two or more different elements are chemically bonded in a fixed ratio, creating a new substance with unique properties (e.g., Water (H2O), Carbon Dioxide (CO2)).
• Mixture: A combination of two or more substances that are physically combined but not chemically bonded, retaining their individual properties and often separable by physical means (e.g., air, salt water, trail mix).