2026S2 Chapter 11 Chemical Changes (Chemistry)

WA2 revision

Chemical formula of hydrochloric acid

HCl

Definition of a neutron

A neutron is a subatomic particle that has no charge and that is found in the nucleus of an atom.

Chemical formula of ammonia

NH3

Chemical formula of methane

CH4

Chemical formula of glucose

C6H12O6

Chemical formula of silver chloride

AgCl

Chemical formula of carbon dioxide

CO2

Acid + alkali

salt + water (neutralisation)

Acid + reactive metal

salt + hydrogen gas (effervescence observed, metal shrinks)

Test for hydrogen

Use a lighted splint: will extinguish with a ‘pop’ sound in the presence of hydrogen

Acid + metal carbonate

salt + water + carbon dioxide (effervescence observed, solid dissolves in acid)

Test for CO2

Bubble the gas into limewater - white precipitate will form in the presence of carbon dioxide.

Definition of combustion

Combustion is when a substance is heated or burnt in the presence of oxygen to form one or more new substances.

Definition of thermal decomposition

Thermal decomposition is when a substance breaks down into two or more simpler substances upon heating.

Definition of an isotope

Isotopes are atoms of the same element with the same proton number but different number of neutrons.

Definition of a proton

A proton is a positively charged particle located in the nucleus of an atom

Definition of an electron

An electron is a negatively charged particle located in the shell of an atom

What makes group 0 atoms stable and very unreactive?

They have a fully filled valence shell

On contact with acid, blue litmus paper…

turns red

On contact with alkali, red litmus paper...

turns blue

On contact with acid, red litmus paper...

stays red

On contact with alkali, blue litmus paper…

stays blue

Definition of oxidation

Oxidation when a substance gains oxygen in a chemical reaction

acid pH..

less than 7

alkali pH..

more than 7

neutralisation pH..

=7

During electroplating, positive terminal of the battery is connected to

the coating metal

During electroplating, the negative terminal of the battery is connected to

the object to be coated

Chemical reactions can be initiated by

heating, mixing, light and electricity

Definition of photodecomposition

Photodecomposition is the breaking down of certain substances into simpler substances when exposed to light.

Definition of electroplating

Electroplating is the process of coating a metallic object with a layer of another metal using electrical means.

atomic number =

proton number

proton number =

atomic number

mass number (nucleon number)

protons + neutrons

How do you find the number of neutrons?

mass number - atomic number

Chemical formula of hydrogen

H2

Covalent bonding is..

the bonding between two co-valence atoms

Covalent bonding is between

two non metals

Ionic bonding is between

one metal and one non-metal

hydroxide implies?

It’s an alkali

In ionic bonding, the ___ atom loses ___ electrons to form a ___ ___.

in ionic bonding, the metallic atom loses valence electrons to form a positive ion.

In ionic bonding, non-metallic atom..

gains electrons to form a negative ion.

Chemical equation for photosynthesis

carbon dioxide + water →glucose + oxygen

Electrolysis

When a current passes through a substance, breaking it down into simpler substances.

Equation for electrolysis of water

water →oxygen gas + hydrogen gas

chemical formula of nitrogen

N2

Chemical formula of oxygen

O2

chemical formula of flourine

F2

Chemical formula of chlorine

Cl2

chemical formula of bromine

Br2

chemical formula of iodine

I2

chemical formula of water

H2O

chemical formula of carbon monoxide

CO

chemical formula of nitrogen monoxide

NO

chemical formula of nitrogen dioxide

NO2

chemical formula of sulfur dioxide

SO2

chemical formula of sulfur trioxide

SO3