Science chapter 11 Flashcards
A mixture can be separated by
separated by physical
methods, e.g. filtration,
distillation or
chromatography.
A compound can only be separated through
chemical reactions or by
using electricity.
The chemical properties of a
mixture are
the same as those of its components.
No chemical reaction takes
place when a
mixture is formed — usually there is
little or no energy change.
The physical and chemical
properties of a compound
are
different from those of
the elements in the compound.
A chemical reaction takes place when a
compound is formed — usually there is an energy change
The components of a mixture
can be mixed in
any proportion.
The elements in a compound
are always combined in a
fixed proportion (by mass).
Changes can be classified as
physical changes or chemical changes
Properties of physical changes (4 properties)
-No new substances are
formed
-No or little heat is taken in or
given out
-Properties of substance
remain the same
-Reversible
Properties of Chemical changes (4 properties)
-One or more new substances
are formed (products)
-Heat and/or light energy may
be taken in or given out
-Properties of products are
different from starting
reactants
-Usually not easily reversible
What is combustion
Combustion is a chemical reaction in which a
substance is heated in the presence of oxygen to
form one or more new substances.
What is the law of conservation
The law of conservation of mass states that mass is always
conserved during a chemical reaction.
Complete
combustion occurs
when there is an
abundant supply of
oxygen.
What is thermal decomposition
Thermal decomposition is a
process in which a substance
is broken down into two or
more simpler substances upon
heating.
During a reaction, mass cannot be…
created or destroyed
What is usually given out during combustion
a lot of Heat and light energy
What does oxidation refer to
Oxidation refers to a chemical change in which a
substance gains oxygen.
Oxidation also occurs during
combustion and cellular respiration
Organic acids are
weak acids
What are two examples of an oxidation process
rusting and corrosion
Mineral acids are
strong acids
Acids have a
SOUR taste
Acids are
corrosive
Acids turn blue litmus paper
red
Acids dissolve in water to form solutions which can
conduct electricity. (electrolyte)
Alkalis taste… and have a … feel
bitter, slippery
Alkalis turn red litmus paper
blue.
When alkalis react with acids, a chemical
reaction called … occurs? What is always formed
neutralisation occurs. Water is
always formed.
acid + alkali ->
salt + water
Dilute acid + metals ->
salt + hydrogen
hydrochloric acid + sodium hydroxide 🡪 sodium chloride + water
hydrochloric acid + potassium hydroxide 🡪 potassium chloride + water
hydrochloric acid + calcium hydroxide 🡪 calcium chloride + water
REMEMBER
Hydrochloric acid(acid)+ sodium carbonate (carbonate)🡪
sodium chloride(salt) + carbon dioxide + water
HOW DO WE TEST FOR CARBON DIOXIDE GAS?
- Add abt 2ml of hydrochloric acid and add 1 spatula of a carbonate to the acid in the test tube
- put a stopper on the test tube
- put abt 2ml of limewater into a separate test tube
- then put a delivery tube into it
- stopper end of the test tube with limewater goes into the test tube with carbonate and hydrochloric acid
- shake to bubble gas into limewater
- warm the test tube gently, moving side to side at the tip of the flame
- if there is carbon dioxide, a white precipitate will form in the limewater
HOW TO TEST FOR HYDROGEN
Put a lit splint into the sample of the gas, if you get a squeaky pop sound when extinguished, it is hydrogen
pH below 7 =
acidic
pH 7 =
neutral
pH above 7 =
alkaline
acid … …. in red litmus paper
remains red
A neutral solution … … in blue litmus paper
remains blue
A neutral solution … … in red litmus
remains red
In a universal indicator, strong acids , pH waht to waht , it will be
0 to 3, red
alkaline solution … … in blue litmus paper
remains blue
in weak alkali (pH waht to what ) it will be what colour
8 to 11, blue
In a universal indicator, in neutral solutions pH waht to waht, it will be variations of waht
6 to 8, green
In a universal indicator, weak acids, pH waht to waht, the colour will be waht tp waht
3 to 6, orange to yellow
strong alkali (pH waht+) it would be
11+, indigo or blue to dark purplle
In a Methyl Orange indicator, a strong acidic solution will be … and a strong alkaline solution will be …
red, yellow
In a Screened Methyl Orange indicator, a strong acidic solution will be … and a strong alkaline solution will be…
violet, green
In a Phenolphthalein indicator, a strong acidic solution will be … and a strong alkaline solution will be…
colourless, pink
Most plants grow best in … soils.
neutral or slightly acidic
pH of soil may become unsuitable for plant growth due to:
-too much fertilisers added to the soil;
-environmental pollution such as acid rain.
To treat acidity in soil, aka liming, add:
-calcium oxide (quicklime);
-calcium hydroxide (slaked lime).
Mixing substances also produces
other… changes.
chemical
Photosynthesis is the process
in which green plants
produce glucose and oxygen from carbon dioxide and
water using light energy.
Heat interacts with different
substances to bring about
many different kinds of
changes.
Photosynthesis is represented with this word equation
carbon dioxide + water ————————>glucose + oxygen
light & chlorophyll
X rays are represented with this word equation
silver bromide————————–> silver + bromine x-ray or light
Cellular respiration is represented using the word equation
glucose + oxygen —-> carbon dioxide +water
Cellular respiration is the process
in which living cells of plants and
animals take in oxygen to release
the energy stored in glucose.
Passing an electric current through a substance
also produces some chemical changes such as
electrolysis and electroplating
define electrolysis
Electrolysis is the chemical decomposition of
substances with the passage of an electric current.
electrolysis is represented using the word equation
water ————–> hydrogen + oxygen
electricity
Electroplating is an application of
electrolysis.
Electroplating is the process
in which a substance is coated with a metal with the passage of an electric current.
the knowledge of chemical reactions
help us in our daily lives
through rusting, pollution and decomposition
Give me an example of electroplating
- An electric current is passed
through the copper sulfate solution.
2.
The copper plate becomes
smaller as the coin becomes
coated with reddish brown copper.
