Chemical Reactions and Changes Quiz

Chemical Reactions

• A chemical reaction is the interaction of substances to create new substances.
• Reactants are the substances that react (on the left of the arrow).
• Products are the substances that are made (on the right of the arrow).
  • Example: A + B → C + D (A and B react to form C and D).

Chemical Change vs Physical Change

• Chemical change occurs when a chemical reaction creates new substances.
• Physical change occurs when no new substances are made.
  • Example: Rusting iron (chemical change) vs. water molecules maintaining the same structure (physical change).

Compound Formulae 1

• Compound formulae use symbols and small numbers to represent the elements and atoms in a compound.
• The small number(s) after an element symbol shows how many atoms of that element are present in the compound.
• Capital letters represent elements, and lower case letters (if any) are part of the element symbol.
• Example: Water (H₂O) has 2 hydrogen atoms, and 1 oxygen atom.

Compound Formulae 2

• "Big numbers" at the start of a chemical formula indicate the number of molecules.
• Example: 2H₂O represents 2 molecules of water, having 4 hydrogen atoms and 2 oxygen atoms.

Writing Formulae From a Structure

• Chemical formulae can be derived from a diagram of a chemical structure.
• Count the number of each type of atom.
• Example: Ethane (C₂H₆) - 2 carbon atoms and 6 hydrogen atoms.

Compound Formulae With Brackets 1

• Brackets in chemical formulae indicate a group of atoms that act as a single unit.
• The number outside the bracket multiplies everything inside the bracket.
• Example: Magnesium hydroxide (Mg(OH)₂) - 1 magnesium atom, 2 oxygen atoms, and 2 hydrogen atoms.

Compound Formulae With Brackets 2

• "Big numbers" at the start of a chemical formula represent the number of molecules containing the grouped atoms.
• Example: 2Mg(OH)₂ has 2 magnesium atoms, 4 oxygen atoms, and 4 hydrogen atoms in total.

Compound Formulae Examples

• Chemical formulae can depict the atoms within compounds.
• Example: Mg(NO₃)₂ has 1 magnesium atom, 2 nitrogen atoms, and 6 oxygen atoms.
• Example: 3Mg(NO₃)₂ has 3 magnesium atoms, 6 nitrogen atoms, and 18 oxygen atoms.

Relative Formula Mass (No Brackets)

• The relative formula mass (Mr) of a compound shows the total atomic mass of all atoms in the compound.
• Calculated by adding the relative atomic mass of atoms in a compound.
• Example: H₂O - (2 × 1) + (1 × 16) = 18

Relative Formula Mass (With Brackets)

• Example: Mg(NO₃)₂ - Mr = (1 × 24) + (2 × 14) + (6 × 16) = 148

Scatter Graphs

• Scatter graphs show the relationship between two variables.
• The independent variable is on the x-axis, and the dependent variable is on the y-axis.
• Data points are plotted, and a line of best fit can be drawn.

Naming Compounds (Words)

• The names of elements change when bonded in compounds.
• Group 7 elements become -ide (e.g., chloride).
• Group 6 elements become -ide (e.g., oxide).
• In more complex compounds, naming parts of the compound names changes depending on the other elements (e.g, sulfate, carbonate).

Naming Compounds (Chemical Formulae)

• Chemical formulae can be used to name compounds.
• Example: NaF - sodium fluoride
• Example: Li₂S - lithium sulfide

Chemical Word Equations

• Word equations use the names of reactants and products in a reaction.
• Example: Carbon + Oxygen → Carbon dioxide

Chemical Symbol Equations

• Chemical symbol equations use chemical symbols to represent reactants and products.
• Example: C + O₂ → CO₂

Test your understanding of chemical reactions, changes, and compound formulae. This quiz will cover the differences between physical and chemical changes, as well as how to interpret compound formulae. Perfect for students looking to solidify their chemistry knowledge!