Forces, Motion, and Chemical Reactions

Vocabulary practice flashcards covering forces, motion, distance-time graphs, ionic chemical formulae, polyatomic ions, and balancing chemical equations.

Speed

The distance travelled by an object per unit of time, calculated using the relationship $\text{speed} = \frac{\text{distance}}{\text{time}}$.

Metres per second ($\text{m/s}$)

The standard scientific unit of measurement for speed and velocity.

Speed Conversion Factor ($3.6$)

The constant factor derived from $\frac{3600\,\text{s}}{1000\,\text{m}}$ used to convert speed units: multiply by $3.6$ to convert $\text{m/s}$ to $\text{km/h}$, and divide by $3.6$ to convert $\text{km/h}$ to $\text{m/s}$.

Discrete Data

Data consisting of distinct, separate values where individual situations do not follow on from each other, making bar graphs or column graphs more suitable than line graphs.

Scientific Graph Plotting Rules

Standards for plotting motion graphs requiring both axes to include labels and correct units, scales set so data spans more than half the grid axes, and points plotted as small crosses ($+$, $\times$) with a sharp pencil.

Motion Graphs (Distance-Time vs. Speed-Time)

Comparative graphs where a straight diagonal line represents constant speed on a distance-time graph but constant acceleration on a speed-time graph, while a flat horizontal line represents being stationary on a distance-time graph but constant speed on a speed-time graph.

Gradient (Rise/Run) on a Distance-Time Graph

The steepness or slope of the line on a distance-time graph, calculated by dividing the vertical rise (distance) by the horizontal run (time), which gives the speed of the object.

Stationary Section (Distance-Time Graph)

A flat, horizontal line with a slope of zero on a distance-time graph, indicating that no distance is being covered and the object has stopped moving.

Average Speed

The overall distance travelled divided by total elapsed time, which is lower than maximum sprint speed in a race because it accounts for acceleration from rest.

Cation

A positively charged ion, such as $\text{Na}^+$, $\text{Ca}^{2+}$, or $\text{Al}^{3+}$, that combines with negative ions in definite ratios to create neutral compounds.

Anion

A negatively charged ion, such as $\text{Cl}^-$, $\text{O}^{2-}$, or $\text{N}^{3-}$, that pairs with positive ions to form electrically neutral compounds.

Electrical Neutrality of Ionic Compounds

The fundamental principle stating that in a chemical formula of an ionic compound, the total positive charge of the cations must equal the total negative charge of the anions.

Chemical Formula of Sodium Oxide

$\text{Na}_2\text{O}$, formed because two sodium cations ($\text{Na}^+$) with charge $+1$ each are required to balance one oxide anion ($\text{O}^{2-}$) with charge $-2$.

Chemical Formula of Calcium Chloride

$\text{CaCl}_2$, formed because one calcium cation ($\text{Ca}^{2+}$) with charge $+2$ balances two chloride anions ($\text{Cl}^-$) with charge $-1$ each.

Polyatomic Ion

An ion composed of two or more covalently bonded atoms carrying an overall net electrical charge, such as sulfate ($\text{SO}_4^{2-}$), nitrate ($\text{NO}_3^-$), or ammonium ($\text{NH}_4^+$).

Chemical Formula of Calcium Nitrate

$\text{Ca}(\text{NO}_3)_2$, consisting of one calcium ion ($\text{Ca}^{2+}$) balancing two nitrate polyatomic ions ($\text{NO}_3^-$).

Chemical Formula of Ammonium Sulfate

$(\text{NH}_4)_2\text{SO}_4$, consisting of two ammonium polyatomic cations ($\text{NH}_4^+$) balancing one sulfate polyatomic anion ($\text{SO}_4^{2-}$).

Reactants

The starting chemical substances that undergo change during a reaction, written on the left-hand side of a word or symbol equation.

Products

The new chemical substances formed during a reaction, written on the right-hand side of a word or symbol equation.

Conservation of Mass

The law stating that the total mass of reactants equals the total mass of products in a chemical reaction because no atoms are created or destroyed.

Diatomic Elements

Elements whose atoms naturally bond in pairs to exist as two-atom molecules: hydrogen ($\text{H}_2$), nitrogen ($\text{N}_2$), oxygen ($\text{O}_2$), fluorine ($\text{F}_2$), chlorine ($\text{Cl}_2$), bromine ($\text{Br}_2$), and iodine ($\text{I}_2$).

Balanced Symbol Equation

A representation of a chemical reaction using chemical formulas with coefficient numbers placed in front so that the count of each atom type is identical on both the reactant and product sides.

Reactant and Product Inventory

A structured count of the number of atoms of each element on both sides of a chemical equation, used to verify whether the equation is balanced.

Balanced Equation for Magnesium Combustion

$2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}$, demonstrating that two atoms of magnesium react with one diatomic oxygen molecule to yield two formula units of magnesium oxide.

Balanced Equation for Aluminium Oxide Formation

$4\text{Al} + 3\text{O}_2 \rightarrow 2\text{Al}_2\text{O}_3$, showing that four atoms of aluminium combine with three diatomic oxygen molecules ($6$ oxygen atoms total) to produce two units of aluminium oxide.