1.1 Introduction to the particulate nature of matter and chemical change
Refresh:
Monday, 14 November 202
Every lesson will begin with a refresher question from the previous class.
Objectives:
Keywords/ processes
Grade 4
Grade 5
Grade 6
• Mixtures are either
heterogeneous or
homogenous
• Use the correct state
symbols (s), (l), (g)
and (aq) in
equations
• Mixtures retain their
individual properties
as they contain
more than one
element and/or
compound that are
not chemically
bonded together
• Deduce chemical
equations when the
reactants and
products are
specified
• Atoms of different
elements combine in
fixed ratios to form
compounds
Recall & remember
Describe & explain
Apply and evaluate
Melting point
Freezing point
Boiling point
Vaporization
Condensation
Sublimation
Evaporation
deposition
Elements and Compounds
©Dr. Geoffrey Neuss thinkIB.net
All pure substances are either made up of just one chemical element, eg. copper metal or
oxygen gas, or are compounds made up of two or more elements, eg. water, carbon
dioxide or glucose.
A chemical element is a neutral substance that cannot be broken down into simpler
substances using chemical methods. It consists only of atoms that contain the same number
of protons and electrons, although the atoms can contain a different number of neutrons.
There are 118 known chemical elements.
A compound is a pure substance formed when two or more chemical elements are
chemically bonded together. A compound has different properties from its component
elements. For example, sodium is a reactive metal which melts at 98ºC and chlorine is a
poisonous reactive gas whereas sodium chloride is a salt with a high melting point (801ºC)
which dissolves in water.
Objective:
•
Atoms of different elements combine in fixed ratios to form compounds
Task 1 - Elements
©Dr. Geoffrey Neuss thinkIB.net
Complete the following lists with the name or symbol for some common
elements using Table 5 of the Chemistry Data Booklet 2016.
Objective:
•
Atoms of different elements combine in fixed ratios to form compounds
States of Matter
There are three common states of
matter:
• Solid (s): occupy a fixed space and a
fixed volume. Particles held closely
together in a lattice.
• Liquid (l): Fixed volume that takes up
the shape of its container. Particles
close together but moving with
random motion.
• Gas (g): Completely fills its container.
Widely spaced particles moving with
rapid, random motion.
Objective:
•
Use the correct state symbols (s), (l), (g) and (aq) in equations
©Dr. Geoffrey Neuss thinkIB.net
Task 2 – States of Matter
©Dr. Geoffrey Neuss thinkIB.net
Explain the meaning of the following words with regards to changes in state:
• melting
• freezing
• vaporization
• evaporation
• boiling
• condensation
• sublimation
• deposition
Objective:
•
Use the correct state symbols (s), (l), (g) and (aq) in equations
Task 3 – Cooling Curves
©Dr. Geoffrey Neuss thinkIB.net
The graph shows the temperature of a sample of naphthalene measured at
one minute intervals as it cools from the liquid state of 90ºC.
Explain the shape of the graph at the molecular level.
Objective:
•
Use the correct state symbols (s), (l), (g) and (aq) in equations
Pure Substances and Mixtures
©Dr. Geoffrey Neuss thinkIB.net
A pure substance may either be an element or a compound and has a definite and
constant composition. A mixture is a physical combination of pure substances. Mixtures have
no definite or constant composition.
A mixture can be separated into its pure components by physical means.
Ways of separating mixtures into their pure components include filtration, distillation and
different forms of chromatography.
A mixture may be homogeneous – all the components are in the same phase or
heterogeneous – the components are in different phases. There is a physical boundary
between two phases so, for example, a mixture of oil and water is a heterogeneous mixture
even though both the oil and the water are in the liquid state.
Objective:
•
•
Mixtures are either heterogeneous or homogenous
Mixtures retain their individual properties as they contain more than one element and/or compound that
are not chemically bonded together
Task 4 – Pure Substances and Mixtures
©Dr. Geoffrey Neuss thinkIB.net
Consider the following mixtures:
• A solution of sodium chloride in water
• An analgesic tablet containing paracetamol, caffeine and codeine
• Unleaded gasoline (petrol)
• Oil and vinegar
1. Identify which of the mixtures are homogeneous and which are
heterogeneous.
2. Suggest how you could separate each of the mixtures into their individual
components.
Objective:
•
Mixtures are either heterogeneous or homogenous
Task 5 - Assumptions
©Dr. Geoffrey Neuss thinkIB.net
In the early nineteenth century John Dalton made the following
assumptions:
• Elements are made of extremely small particles called atoms.
• Atoms of a given element are identical in size, mass, and other
properties; atoms of different elements differ in size, mass, and
other properties.
• Atoms cannot be subdivided, created, or destroyed.
• Atoms of different elements combine in simple whole-number
ratios to form chemical compounds.
• In chemical reactions, atoms are combined, separated, or
rearranged.
Discuss whether each of these five assumptions is still considered to
be valid today.
Objective:
•
Mixtures retain their individual properties as they contain more than one element and/or compound that
are not chemically bonded together
Chemical Equations
©Dr. Geoffrey Neuss thinkIB.net
In a chemical equation reactants are written on the left-hand side and products on the right-hand side.
The coefficient refers to the number in front of each reactant and product in the equation. The coefficients give
information on the molar ratio.
In a balanced chemical equation the amount (in moles) of each element must be the same on both sides as there
is no overall change in mass during a chemical reaction.
The states of the reactants and products are represented by (g), (l), (s) and (aq) where (aq) refers to ‘in aqueous
solution.’
Reversible arrows are used to represent equilibrium reactions.
CaCO3(s) + 2HCl(aq)  CaCl2(aq) + CO2(g) + H2O(l)
(single arrow as reaction goes to completion)
N2(g) + 3H2(g) ⇌ 2NH3(g)
(reversible arrows as reaction is in equilibrium)
Objective:
•
•
Use the correct state symbols (s), (l), (g) and (aq) in equations
Deduce chemical equations when the reactants and products are specified
Key Points
• Physical and chemical properties depend on the ways in which different
atoms combine.
Objective: