7H - Atoms, molecules, elements and compounds Flashcards
What is a molecule?
More than one atom bonded together.
What are mixtures?
Materials that contain more than one substance which are NOT joined together.
What happens if a natural material is pure?
Contains only one substance (isn’t mixed).
What are elements?
Substances made out of only one type of atom.
What are compounds?
Substances made out of more than one kind of atom (element) bonded together.
What is O?
Oxygen
What is Mg?
Magnesium
What is Fe?
Iron
What is Si?
Silicon
Where do we obtain all the elemnts and compounds we need from?
From the earth’s atmosphere and crust.
Why is it important to recycle?
Because our resources are limited and some may run out in the near future.
What are the 5 common properties of metals?
- High melting point
- Strong and flexible
- Shiny
- Good conductors of heat
- Good conductors of electricity
What are the 5 common properties of non metals?
- Low melting points
- Brittle
- Not shiny
- Poor conductors of heat
- Poor conductors of electricity
What determines the uses of a material?
Its properties.
i.e. copper is strong, flexible and conducts electricity so its used for electricity cables.
What is the name of the only liquid metal?
Mercury
What is the first name of a compound if there’s a metal present?
The name of the metal
What is the second name of a compound with only two elements?
one element name has its name ending changed to -ide
(i.e. sodium + chlorine = sodium chloride)
If a compound contains two elements plus oxygen, what is its second name?
The name of an element with its ending changed to -ate.
(i.e. magnesium + nitrogen + oxygen = magnesium nitrate)
What do chemical reactions always form?
New substances
What are the typical signs of a chemical reaction taking place?
- Colour change
- Gas given off
- Solid being formed
- An energy change
If a chemical reaction doesn’t need heat to continue reacting, does it need heat to start reacting?
Some reactions need heat to start, but once started they give off heat.
(i.e. burning petrol)
Do all reactions need heat to start?
No. some just start reacting by getting mixed.
(i.e. acids and alkalis)
Name a reaction that needs a continuous supply of energy (heat) to keep on going.
Breaking down metal ores
Give examples of chemical reactions
Burning, cooking, rusting, digesting food.
What happens during thermal decomposition reactions?
A single compound is broken down using heat.
(i.e. Tin carbonate > tin oxide + carbon dioxide)
What is the word equation for the thermal decomposition of copper carbonate?
Copper carbonate > copper oxide + carbon dioxide
What is the main use of thermal decomposition reactions?
used in industry to extract metals from metal ores.
What is the percentage of nitrogen in air?
78%
What is the percentage of oxygen in air?
21%
What is the percentage of ‘other’ gases that aren’t oxygen or nitrogen in air?
1%
