CHEMICALS AND CHEMICAL CHANGE

Chapter 5.1 BLM 5.1a, 5.1b

Chemicals and Chemical Change

CHEMISTRY – is the study of matter, its changes and its properties.

MATTER – is anything that has mass and takes up space. See excerpt from Bill Bryson

ATOM – the smallest particle of matter. see excerpt from Bill Bryson

Pure Substances

A pure substance is one in which all the particles that make up the substance are the same.

• Ex. Water – clear, colourless and boils and freezes at the same temperatures.

• Pure Substances are classified as elements or compounds.

Elements

Elements are pure substances that cannot be broken down into simpler substances.

Ex. Oxygen, hydrogen, iron and mercury are elements because each contain only one kind of atom.

Compounds

Compounds are pure substances that contain two or more different elements in a fixed proportion.

Ex. Carbon Dioxide – CO2 is a compound where each molecule is composed of one Carbon atom and two Oxygen atoms.

Ex. Water – H20 is composed of 2 Hydrogen atoms and one Oxygen atom.

Properties of Matter

Physical Properties are characteristics of a substance.

Ex. Baking Soda – a white, crystalline solid at room temperature that dissolves

readily in water to form a solution

Chemical Properties

A Chemical Property is a characteristic of a substance when a substance changes to a new substance.

Ex. Baking Soda and vinegar produces carbon dioxide.

PHYSICAL CHANGE – a change in a substance

which does not produce a new substance.EXAMPLE: melting ice become water in a liquid state

CHEMICAL CHANGE – a change in a substance which produces a new substance.

EXAMPLE: match burning

Chemical Changes The starting materials in chemical changes are

called reactants and the new materials produced are called products.

Ex. Iron and Oxygen are reactants and iron(III) oxide is a product.

Using page 173, figure 4 make notes on the clues of chemical changes.

Use the following labels and pages 173 – 174 to complete the handout.

Rusting/corrosion difficult to reverse,water vapor turns cloudynew color reactantsPops oxygenturns pink products,Precipitate carbon dioxide,bursts into flames heat or lightHydrogen oxygen

HANDOUT 5.1b

Use the following labels and pages 173 – 174 to complete the handout

Rusting/corrosion difficult to reverse,water vapor turns cloudynew color reactantsPops oxygen (x2)turns pink products,Precipitate carbon dioxide,bursts into flames heat or lighthydrogen

Reactants

Products

Corrosionor Rusting

OxygenTough

to reverseEnergy

Given offPrecipitate

forms

H2 O2 H2OCO2

Pops Bursts intoFlames

TurnsPink

TurnsCloudy

Colour

Change

QUESTIONS

Page 175 QUESTIONS: #1,2,4,5,6,7

SOLUTIONS TO HOMEWORK QUESTIONS

Q1 – classify each of the following as a pure substance or a mixture

A) soapy water MIXTURE

B) hydrogen gas PURE SUBSTANCE

C) sodium chloride PURE SUBSTANCE

QUESTION 2Classify each of the following as an element or a

compound.A) hydrogen

ELEMENTB) potassium carbonate

COMPOUNDC) water

COMPOUNDD) Mg

ELEMENT

QUESTION 4

Classify each of the following as a physical property or a chemical property.

A) Gasoline is a clear pink solutionPHYSICAL PROPERTY

B) Gasoline burns in airCHEMICAL PROPERTY

C) Water boils at 1100C. PHYSICAL PROPERTY

D) electric current can split water into hydrogen and oxygen gases CHEMICAL PROPERTY

QUESTION 5

When aluminum metal is added to hydrobromic acid, hydrogen gas and an aluminum bromide solution are formed.

A) What kind of change has occurred?

Chemical, bubbles formed, new substance made

QUESTION 5

When aluminum metal is added to hydrobromic acid, hydrogen gas and an aluminum bromide solution are formed

B) Which substances are the reactants and which are the products?

Reactants – Aluminum and AcidProducts – Hydrogen + Aluminum Bromide

QUESTION 6

Describe the chemical tests that can be used to identify the following gases.

A) hydrogen a flaming wooden splint causes a “pop”

B) Oxygen a glowing wooden splint relights (bursts into flame)

QUESTION 6

C) Carbon Dioxide

A burning wooden splint extinguishes, OR when the gas is bubbled through limewater, the limewater changes from a clear, colourless solution to a cloudy white liquid (a precipitate is formed)

QUESTION 6

Water Vapour

Changes the colour of cobalt chloride test paper from blue to pink

QUESTION 7

When sodium carbonate is added to water, the sodium carbonate dissolves. When hydrochloric acid is added to the solution, the solution fizzes. What kinds of changes have occurred?

QUESTION 7 - ANSWER

When sodium carbonate dissolves in water it is a physical change

A chemical change happens when gas is formed after hydrochloric acid is added ( fizz / Bubbles )

Homework

Physical or Chemical change:• Tell me why• Value: 15 marks

• (1 mark for whether it is chemical or physical)• (2 marks for your reasoning)