Chap 5 : Chemical Changes Flashcards
What are changes?
Changes are a result of interactions between matter and energy
How are changes classified?
Changes can be classified as chemical changes or physical changes.
What are examples of physical changes?
Dissolving sugar or salt in
water and evaporation are
examples of physical changes.
Are physical changes reversable?
Physical changes are
reversible and do not involve
the formation of new
substances.
Are chemical changes irreversable?
Chemical changes are irreversible and involve the
formation of new substances.
Energy in the form of heat, light or electricity may
be taken in or given out during a chemical change.
Is rusting a physical or chemical change?
Iron reacts with oxygen and
water in the air to form rust.
Rust is a brown substance.
Hence, rusting is a
chemical change.
What are some examples of chemical changes?
rusting,
burning of paper,
photosynthesis
souring of milk
What are chemical changes also known for?
Chemical changes are also known as chemical
reactions.
When do chemical changes occur?
Chemical changes occur when matter interacts
with heat, light or electricity
and other kinds of matter
How are chemical changes represented?
Chemical changes can be represented by word equations.
What is a reactant/reactant(s)?
-Found to the left of the
arrow
-Substances present at
the start of the reaction
What is a condition/condition(s)?
Found in the middle of the arrow
A condition/condition(s) are Factors (e.g. heat, light and pressure) required for the reaction to take place
Represents order and
direction of the reaction.
What is a product/product(s)?
-Found to the right of the
arrow
-Substances present at the
end of the reaction
What is an example of a chemical reaction?
Burning charcoal is an example of a chemical reaction.
What is the chemical reaction of Burning charcoal?
Carbon and oxygen are the reactants
The condition is heat
and carbon dioxide is the product
Do The products of a chemical reaction have different
properties from that of the reactants.
Chemical energy stored in the charcoal is converted to
heat and light energy.
The products of a chemical reaction have different
properties from that of the reactants.
Chemical energy stored in the charcoal is converted to
heat and light energy.
How are fireworks displayed in the sky?
- Fireworks display brilliant colours in the sky.
- Different chemical compounds in the fireworks produce the different colours.
- When the compounds are burnt, they undergo chemical reactions to produce an amazing display of light.
What is mixing?
-Light sticks are often used during
special occasions.
-The changes within the light stick
is an example of a chemical
change that is produced when
mixing substances.
-A light stick contains two chemicals that are kept separate in an external casing and a smaller, thinner tube on the inside.
2. When the stick is bent, the inner tube breaks and releases the chemical inside . -Mixing substances also produces other chemical changes.
-Dilute acids produce chemical
changes when mixed with rust.
-We can use this property to remove
rust stains.
What is an example of a chemical change during mixing?
Antacids are usually
prescribed for gastric pains.
Gastric pains are felt when
too much gastric juices are
produced in the stomach.
Antacids react with
hydrochloric acid found in
gastric juice to form a
harmless product.
This provides relief for
gastric pains.
Elaborate on heating.
When we cook an egg, a chemical
change occurs.
The process is a chemical
change as the reaction is
irreversible.
Heat interacts with different
substances to bring about
many different kinds of
changes.
What is thermal decomposition?
Thermal decomposition is a process in which a substance is broken down into two or more simpler substances by the effect of heat.
What is an example where thermal decomposition takes place?
Sugar breaks down into carbon and
water vapor when heated for too long.
This process is known as thermal decomposition.
What is another example where thermal decomposition take place?
Limestone undergoes thermal decomposition in order
to produce glass.
Limestone is mainly made up of calcium carbonate.
This process is a chemical change as calcium carbonate has interacted with heat to form new products.
Elaborate on the interactions between matter and oxygen
When we expose objects such as bicycles and chains to
the environment for a long time, parts of these objects
made of iron or steel may turn rusty.
Such objects become rusty when the iron or steel reacts
with oxygen in the presence of water or moisture.
Rusting is an oxidation process.
What is oxidation?
Oxidation is a chemical change in which a substance
reacts with oxygen.
When does oxidation occur?
Oxidation also occurs during
– combustion; and
– cellular respiration.
