9G - GCSE Chemistry Basics Flashcards
Ions
when an atom gains/loses electrons (this is because they gain a charge)
Lose electrons
positive charge +
Gain electrons
negative charge -
Outermost shell
Valence
Most atoms form bonds with
either the same or different element
An ionic bond
is when two elements of different groups share electrons in order to form a positive and a negative ion. These two ions attract each other and bond
A Covalent bond
is when two or more pairs of electrons are shared between two atoms. They are simultaneously attracted to each other, binding them in a fixed position.
A Metallic bond
is when two metals share a sea of valence electrons between several positively charged metal ions. The more electrons, the less malleable the metal is (because there is a stronger force between opposite charges).
applying voltage
a potential difference
By applying voltage (a potential difference) to two different points on a metal
all the electrons will flow in the same direction
By ensuring the electrons can move in an ionic bond
you can also have an electrical current, e.g. molten sodium chloride will be conductive but a solid form won’t.
Physical changes
are when their is a change of shape, state or size. e.g. a substance melts, evaporates, e.t.c., which requires energy. The energy breaks the bonds, the stronger the bond, the more energy is needed.
Melting and evaporating require
an input of energy, meaning they’re endothermic
The energy that enters makes the particles
move faster and increases the temp. which causes the bonds to break. The temp. of surrounding objects will decrease.
Freezing and condensation require
an output of energy, meaning they’re exothermic.
Particles slow down, allowing
bonds to form. The temp. of surrounding objects will increase.
Chemical reactions are when
new bonds form between different types of atoms, causing a new substance to form. When bonds form, energy is taken in and when bonds break, energy is released, determining whether or not the reaction is endothermic or exothermic.
A rate of reaction is
how fast a reaction takes place
To measure the rate of reaction, we either
measure how quickly the reactants are used up or how quickly the products are formed.
The mean rate of reaction
total volume / time taken
For particles to react, they need to
collide with each other
To increase the rate of reaction you can,
increase the temp. (increasing the speed and energy of particles), increase the surface area (increasing the area which particles can react with meaning there are more reactions)
DON’T FORGET state symbols
DON’T FORGET state symbols
Chemical equilibrium is when
both reactants and products are present but have no further change in time because they have reached a state in which they even eachother out.
