Science Mixtures and Changes Quiz

Heterogeneous Mixtures

• A heterogeneous mixture is a mixture where the components are not evenly distributed throughout the mixture.
• Examples of heterogeneous mixtures include:
  • mud
  • a rock
  • sour cream
  • a precipitate in water

Mixtures

• Mixtures are substances that are made up of two or more components that are not chemically bonded together.
• Examples of mixtures include:
  • seawater
  • air
  • concrete

Elements and Compounds

• An element is a pure substance that cannot be broken down into simpler substances by chemical means.
• A compound is a pure substance that is made up of two or more elements that are chemically bonded together.
• Examples of elements:
  • Iron (Fe)
  • Nitrogen (N)
• Examples of compounds:
  • Water (H2O)
  • Sodium chloride (NaCl)

Physical and Chemical Changes

• A physical change is a change in the form or appearance of a substance, but not its chemical composition.
• A chemical change is a change that results in the formation of a new substance with a different chemical composition.
• Examples of a physical change:
  • water changing from a liquid to a solid (ice)
• Examples of chemical changes:
  • burning a match

Filtration

• Filtration is a process used to separate a solid from a liquid

Molecules

• A molecule is formed when two or more atoms bond together.
• Examples of molecules include:
  • Nitrogen (N2)
  • Water (H2O)

Representing Elements, Compounds, and Mixtures

• An element can be represented by a single atom (X).
• A compound can be represented by a group of atoms that are bonded together (Y).
• A mixture can be represented by a combination of different elements and compounds (Z).

Isotopes and Atomic Structure

• Isotopes are atoms of the same element with the same number of protons (atomic number) but different numbers of neutrons.
• Atomic number of an element is the number of protons in the nucleus of an atom.
• Mass number of an atom is the sum of protons and neutrons in the nucleus.
• Neutral atoms have the same number of electrons and protons.

Molar Mass and Isotopic Abundance

• Molar mass is the mass of one mole of a substance.
• Isotopic abundance is the percentage of each isotope found in a naturally occurring sample of an element.
• The molar mass of an element is the average of the masses of its isotopes, weighted by their abundances.
• Formula for calculating molar mass: (Isotope AM 1 x % Abundance) + (Isotope AM 2 x % Abundance) /100

Empirical Formula

• Empirical formula represents the simplest whole-number ratio of atoms in a compound.

Chemical Reactions

• Chemical reactions involve the formation or breaking of chemical bonds.
• Dissolution, condensation, burning, rusting, and mixing of chemical solutions can all be examples of chemical reactions.

Temperature Scales

• Kelvin (K) and Celsius (°C) are common temperature scales.
• Conversion Formula: K = °C + 273.15

Number of Electrons, Protons, and Neutrons

• The number of neutrons in an atom can be calculated by subtracting the atomic number from the mass number.
• The number of electrons in a neutral atom is equal to the number of protons.

Determining Number of Electrons in Ions

• Ions are atoms that have gained or lost electrons.
• Cations are positively charged ions formed by losing electrons.
• Anions are negatively charged ions formed by gaining electrons.
• To determine the number of electrons in an ion, add or subtract the number of electrons gained or lost from the neutral atom.