Objective 8 - Properties of matter:
- Element - only one type of atom, contain same number of protons
- Compound - a substance with 2 or more elements (different) chemically bonded together
- e.g. $Cl_2$ is not a compound, there are 2 atoms bonded but they are not different.
- Thus, $Cl_2$ is an element. (Note $Cl_2$ is found in nature rather than Cl.)
- $NaCl$ is a compound. They form an ionic bond, and they are different.
Sodium chloride is a lot of sodium ions attracted to chloride ions, which are attracted to sodium ions. This forms NaCl as a lattice (Note: lattice only refers to ionic compounds), as these ions occur in an equal ratio.
- Molecules: Elements bonded covalently.
- e.g. $Cl_2$ is a molecule
- $SO_2$ is a molecule. also, it is a compound.
Atom:
- Smallest particle of an element that can exist on its own.
Molecule:
- A particle containing two or more atoms joined together by covalent bonds. - has to involve non-metals. - by definition, considering covalent bonds
- Examples: $CO_2$, $H_2O$, $H_2$, $I_2$
Ion:
- An atom or groups of atoms that has become positively or negatively charged by losing or gaining electrons.
- Positively charged - cation (+ve) - formed by losing electrons
- Examples, any metal, $NH4^+$
- Negatively charged - anion (-ve) - formed by gaining electrons
- anions are attracted to cathodes - Michael Faraday
Mass of conservation: no matter can be created nor destroyed.
Element:
- The simplest kind of substance that cannot be broken down into anything simpler. All its atoms have the same number of protons
- All its atoms have the same number of protons.
Compound:
- A substance made from two or more different elements chemically combined together.
Chemical symbol
- Letter of pair of letters used to represent an element
- Examples, S, Fe
Chemical formulae:
- The molecular formula gives the total number of atoms of each element present in one molecule.
- Examples - $N_2$, $C_6H_{12}O_6$
- The empirical formula gives the simples whole number ratio of atoms of each element present in a compound
- Examples - $Na^+Cl^-$ , $CH_2O$
- Chemical formula includes both molecular and empirical.
Stoichiometry is a ratio of substances in an equation when they react.
- When you balance a formula, you put stoichiometric coefficients.
- It is used in calculations.
- The relationship between the relative quantities of substances taking part in a chemical reaction.
Chemical equation:
- Shows the reactants taking part in a chemical reaction and the products from the reactants in the correct proportions.
- Reactants are on the left, and products are on the right.
Pure substances:
- Have a fixed or constant composition
- Cannot be separated by physical means
- Have well defined physical properties, e.g.:
- melting point
- boiling point
- hardness
- density
- colour
- solubility
- conductivity
- Have constant chemical properties.
Mixtures:
- contains two or more different substances, in proportions that can vary
- properties vary with composition, depends on the identity and amounts of constituents/substances
- properties of individual constituents/substances can be used to separate the mixture
Homogenous materials:
- have uniform composition throughout
- includes all pure substances (elements and compounds) and some mixtures
- the only kind of mixture that is homogenous is a solution e.g. salt water
Heterogenous materials:
- heterogenous materials are non-uniform - you can see differences from one section to another
- the constituents are physically separated, e.g. in a different phase
- Examples include:
- Granite (mixtures of different mineral grains)
- Milk (fat globules suspended in water)
- Toothpaste (solid particles suspended in liquid)
Solution:
- Where a minor component (the solute) is uniformly distributed within a major component which is usually a liquid (the solvent)
3 States of matter:
- Solid - molecules are closely bonded together, usually in firm chemical structures. Low kinetic energy - has fixed volume
- Liquid - molecules are loosely bonded together, there are some small chemical bonds, flows freely and is not found in firm states. Medium kinetic energy - has fixed volume
- Gas - weak attraction in molecules, high kinetic energy. Gasses attempt to fill the space of their containment.
Processes of change:
- Gas to liquid - condensation
- Liquid to gas - evaporation
- Solid to liquid - melting
- Liquid to solid - freezing/solidification
- Solid to gas - sublimation
- Gas to solid - deposition
Classification of matter:
Note - mixtures can be separated into pure substances using differences in physical properties.
Pure substances:
Note - compounds are separated by chemical means
Mixtures:
-
Homogenous mixtures - you can shine light through a mixture, if it passes through and light does not change, it is homogenous
-
Heterogenous mixtures - if light scatters, it is heterogenous
Solutions (aq) are mixtures!!! :) thank you ethan widjaja
Chemical Equations Homework 1:
a) $HCl_{(aq)}\ + \ NaOH_{(aq)} \rightarrow NaCl_{(aq)} \ + \ H_2O_{(l)}$
b) $ZnO_{(s)} \ + \ Ca_{(s)} \rightarrow Zn_{(s)} \ + \ CaO_{(s)}$
c) $NH_4OH_{(aq)} \ + \ HCl_{(aq)} \rightarrow NH_4Cl_{(aq)} + H_2O_{(l)}$
d) $H_2SO_{4(aq)} \ + \ Ca(OH){2(s)} \rightarrow CaSO{4(aq)} + 2H_2O_{(l)}$
e) $2KI_{(aq)} + Cl_{2(g)} \rightarrow 2KCl_{(aq)} + I_{2(g)}$
f) $3ZnO_{(s)} + 2Al_{(s)} \rightarrow 3Zn_{(s)} + Al_2O_{3(s)}$
g) $MgCO_{3(s)} + 2HCl_{(aq)} \rightarrow + MgCl_{2(aq)} + CO_{2(g)} + H_2O_{(l)}$
h) $3Mg_{(s)} + 2H_3PO_{4(aq)} \rightarrow Mg_3(PO_4){2(s)} + 3H{2(aq)}$
i) $CaCO_{3(s)} \rightarrow CaO_{(s)} + O_{2(g)}$
j) $CaCO_{3(s)} + CO_{2(g)} + H_2O_{(l)} \rightarrow Ca(HCO_{3})_{2(s)}$
Exercise - writing equations:
a) $Ca(HCO_3){2(aq)} \rightarrow CaCO{3(s)} + CO_{2(g)} + H_2O_{(l)}$
b) $2Na_{(s)} + 2H_2O_{(l)} \rightarrow 2NaOH_{(aq)} + H_{2(l)}$
c) $2H_{2(g)} + O_{2(g)} \rightarrow 2H_2O_{(l)}$
d) $Fe_2O_{3(s)} + 2Al_{(s)} \rightarrow Al_2O_{3(s)} + 2Fe_{(s)}$
a) $Zn_{(s)} + 2HCl_{(aq)} \rightarrow ZnCl_{2(aq)} + H_{2(g)}$
b) $BaCl_{2(aq)} + H_2SO_{4(aq)} \rightarrow BaSO_{4(s)} + 2HCl_{(aq)}$
c) $CuSO_{4(aq)} + 2NaOH_{(aq)} \rightarrow Cu(OH){2(s)} + Na_2SO{4(aq)}$
d) $Cl_{2(g)} + 2KBr_{(aq)} \rightarrow 2KCl_{(aq)} + Br_{2(s)}$
