1. Stoichiometric Relationships
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What are elements?
Elements are substances made from one kind of atom
What are compounds?
Compounds are made from two or more elements chemically combined
What is a mixture?
In a mixture, elements and compounds are interspersed with each other, but are not chemically combined
What characteristics do components in a mixture have?
This means the components of a mixture retain the same characteristic properties as when they are in their pure form
What is a homogenous mixture?
A homogeneous mixture has uniform composition and properties throughout
What is a heterogeneous mixture?
A heterogeneous mixture has non-uniform composition, so its properties are not the same throughout
How could you differentiate between a homogenous and a heterogenous mixture? (qualitative)
It is often possible to see the separate components in a heterogeneous mixture, but not in a homogeneous mixture
How could you separate air?
fractional distillation - using boiling points
How could you separate sand and salt?
solution and filtration by using solubility in water
How could you separate pigments in food colours?
paper chromatography
How could you separate sulfur and iron?
Use a magnet - magnetism
What happens. to substances in aqueous solutions?
In aqueous solutions, ionic compounds dissociate into their ions
What are spectator ions
The ions that do not take part in the reaction are called spectator ions
What is an ionic equation? What does it show?
An ionic equation shows only the ions or other particles taking part in a reaction, without showing the spectator ions
What types of changes are changes of state?
Changes of state are physical changes that are reversible
Why are state changes not considered chemical changes?
These changes do not change the chemical properties or chemical makeup of the substances involved
WHat 2 state changes fall under the category of vaporisation?
Vaporization includes evaporation and boiling
WHat is the difference between evaporation and boiling?
Evaporation involves the change of liquid to gas, but unlike boiling, evaporation occurs only at the surface and takes place at temperatures below the boiling point
WHen does boiling occur?
Boiling occurs at a specific temperature and takes place when the vapour pressure reaches the external atmospheric pressure
What happens between stages 1&2 on a heating curve?
Between 1 & 2, the particles are vibrating and gaining kinetic energy and the temperature rises
What happens between stages 2&3 on a heating curve?
Between 2 & 3, all the energy goes into breaking bonds – there is no increase in kinetic energy or temperature
What happens between stages 3&4 on a heating curve?
Between 3 & 4, the particles are moving around and gaining in kinetic energy
What happens between stages 4&5 on a heating curve?
Between 4 & 5, the substance is boiling, so bonds are breaking and there is no increase in kinetic energy or temperature
What happens between stages 5&6 on a heating curve?
From 5 & 6, the particles are moving around rapidly and increasing in kinetic energy