Chemical & Physical Change Review

Properties of Matter
 Brittleness - the property of matter that is how easily the
substance breaks or shatters when force is applied to it.
 Ductility - property of a metal in which it can be stretched
without breaking.
 Elasticity - the ability of a substance to be stretched and then to
return to its original shape.
 Hardness - property of matter that determines how easily the
substance can be scratched.
 Malleability - the property of a metal that allows it to be
hammered, rolled, pressed or forged.

HOW DOES ONE STUDY FOR A
LAB?
 Practice with the tools, e.g. thermometer, scales, weighing tray,
stopwatch, calculators
 Practice making graphs, especially line graphs (x: time, y:
temperature), using data tables
 Memorize the definitions of key science words
 Use other sources for quizzing, e.g. BrainPop,
aboutChemistry.com
 Make own quiz/test
 Have a peer/parent quiz you on definitions/method

KEY WORDS: CHEMICAL
CHANGE
 Chemical change
 Endothermic reaction
 Exothermic reaction

CHALLENGE
Is cooking an example of
chemical or physical change?

Cooking
 When most of the food is cooked, it can not be reversed to
the original substance it was in before cooking it, for
example, when meat is cooked it changes the color.

chemical change
 A chemical reaction is a chemical change which forms new substances;
the starting materials (reactants) are different from the product
 When a chemical change takes place there is the change of
temperatures where there might be loss of heat but in most chemical
change reactions heat or energy is produced.
 Another characteristic of a chemical change is the change in color. For
example when an iron nail comes into contact with water, the nail
begins to rust and its color change from silver to reddish brown
meaning that chemical change has taken place.
 The production of gases and solids is also another characteristic of a
chemical change.The gases produced appear in the form of bubbles as
a result of the reaction. A solid maybe formed and it separates itself
from the solution after the reaction.

BrainPop Movie
 http://www.brainpop.com/science/matterandchemistry/pr
opertychanges/preview.weml

Endothermic reaction
 An endothermic reaction is any chemical reaction that absorbs
heat from its environment. It is a reaction that requires energy to
proceed.The intake of energy may be observed as a decrease in
temperature as the reaction proceeds. Once the reaction is
complete, the temperature of the mixture will return to room
temperature.
 Examples
1.
2. reacting ethanoic acid with sodium carbonate
3. photosynthesis (chlorophyll is used to react carbon dioxide plus
water plus energy to make glucose and oxygen)

Exothermic reaction
 Many chemical reactions release energy in the form of heat, light,
or sound.These are exothermic reactions.
 Exothermic chemical reactions produce heat.
 Examples
1. In this reaction vinegar is used to remove the protective coating
from steel wool, allowing it to rust.When the iron combines with
oxygen, heat is released.

Collecting Data
Endothermic Exothermic
InitialTemperature °C °C
FinalTemperature °C °C
Temperature change
rate

Law of
Conservation
of Mass
CHALLENGE: EXPLAIN
WITH EXAMPLE

Law of Conservation of Mass
 the mass of substances produced (products) by a chemical
reaction is always equal to the mass of the reacting
substances (reactants).
 in a chemical reaction, the mass of the products equals the
mass of the reactants.
 Example
1.00g carbon + 5.34g sulphur 6.34g carbon disulphide

How do I study for a Science quiz?

Types of Science Questions
KNOWLEDGE What is the freezing point of water?
COMPREHENSION Explain the difference between physical
and chemical change?
ANALYSIS Which is a physical change and why?
Sugar dissolved in water
Burning paper turning into ash
SYNTHESIS In cold countries salt is strewn on icy
roads. Explain the scientific reason ing
behind this.

Key words: Physical Change
 Boiling point
 Melting point
 Sublimation
 Deposition
 Solidification or Freezing
 Evaporation
 Filtration (separation technique)
 Solution = Solute + Solvent

What is a physical change?
Give a real life example
of a physical change?

Requires energy from environment
Cooling Process
Releases energy to environment
Warming Process

Changes in States of Matter
Deposition
Evaporation
Solidification/Freezing
Melting
Sublimation
Condensation

Temperature(degreesCelsius)
Time (minutes)
0
100
Time-Temperature Graph for Water
Why is the slope of the graph flat (no temperature change) at 0 degrees?
Why is the slope of the graph flat (no
temperature change) at 100 degrees even
though the stove is still on?
What is true for the ice-water mixture when the
temperature began to rise?
Why did temperature increase at a constant rate?
When will the temperature of the water rise above 100 degreesCelsius?

Temperature(degreesCelsius)
Time (minutes)
0
100
Time-Temperature Graph for Water
As the temp approaches melting point temperature, the KE of the
water molecules increases loosening the bonds between water
molecules.
As the ice begins to melt, additional heat energy does not raise
the temperature of the water, but loosens the bonds changing
ice to water. i.e. phase change – melting.
Once the water is in a liquid phase, increasing the amount
of heat input raises the temp of the liquid water.
As the temp approaches boiling point, the KE of
the molecules is sufficient to allow the
separation of molecules into the gas phase.
As the liquid begins to boil. Additional
input of heat energy does not raise the
temperature of the water, rather it is used
to break water bonds. i.e. phase change.
Once the water is in the gas phase, additional heat input raises the
temperature of the water vapor Note: greater energy is needed to
vaporize water than to melt it.WHY?

Phase Change- _________
energy from stove = energy required for phase change
____ temperature change
Phase Change- ___________
______ temperature change
Energy from stove causes
increased ____E and increased ___________
increased ___E and increased _____________
______ states of
Matter
______ states of
Matter
_____ states of
Matter

Phase Change- Melting
No temperature change
Phase Change-Vaporization
No temperature change
increased KE and increasedTemperature
increased KE and increasedTemperature
Two states of Matter
Two states of Matter
One states of Matter

Boiling point
 temperature at which a liquid changes to a gas

Melting point
 the temperature at which a substance changes from a
solid to a liquid.

Solidification (freezing)
 changing of a liquid to a solid

Salt on snow-covered roads?
 If you live in an area with a cold and icy winter, you have
probably experienced salt on sidewalks and roads, used to
melt the ice and snow and keep it from refreezing.
 Salt is also used to make homemade ice cream.
 In both cases, the salt works by lowering the melting or
freezing point of water.The effect is termed 'freezing point
depression'. ”
 So, when you add a salt to ice with a little bit of water, the salt
lowers the freezing point of the water, keeping it from re-
freezing as easily and helping to melt the rest of the ice.

Sublimation
 the changing of a solid directly to a gas
 Example
Dry ice is solid carbon dioxide. At room temperature and
pressure, it sublimates into carbon dioxide vapor.

Deposition
 this is a phase change from a gas directly to a solid
Iodine test:
http://www.youtube.com/watch?v=4fAOI6BeMZY
Dry Ice
The Iodine
Test

Evaporation
 changing of a liquid to a vapor at any temperature below
its boiling point.

Alcohol Water Oil
NATURE OFTHE
SUBSTANCE
Why does alcohol evaporate faster?

2. Copy and complete the following sentences using the words
below:
Solution solvent solute saliva
dissolves exposed saliva
The candy dissolves in the ……………………..in your mouth
to form a liquid …………………………..
Solutions contain two parts, a ………………….. and a
……………………………….
The solvent is …………………….. and the solute is the candy.
The solute……………………….. by spreading out evenly
throughout the solvent.
The candy can quickly dissolve when it is ……………… to
chewing and stirred by moving it around with the tongue.

Ms Pommeroy cooks rice in a
pressure cooker. Why?
 A pressure cooker is a sealed pot.
 Steam trapped inside the pot under pressure allows the
temperature to rise beyond what it could reach normally in a
traditional uncovered pot.
 As the pressure inside the cooker increases, the boiling point of
the water inside increases as well.This causes the food to cook at
a higher temperature, which cooks it faster.

CHEMICAL CHANGE PHYSICAL CHANGE
In a chemical change where there is a
chemical reaction, a new substance is
formed and energy is either given off or
absorbed.
A physical change in a substance doesn't
change what the substance is.
If a piece of paper is burned, it is broken up
into different substances that are not paper.
For example, if a piece of paper is cut up into
small pieces it still is paper.This would be a
physical change in the shape and size of the
paper.
Chemical changes cannot be reversed with
the substance changed back without
extraordinary means, if at all.
Physical changes can be reversed.
If one made a recipe for a cake with flour,
water, sugar and other ingredients and
baked them together, it would take
extraordinary means to separate the various
ingredients out to their original form.
If one decided to mix sugar/salt into water
to make sugar/salty water, this would be a
physical change as the water could be left
out to evaporate and the sugar/salt crystals
would remain.
Note: remember salt is sodium chloride
(NaCl)

Chemical & Physical Change Review

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