6.4 Chemical Reactions Flashcards
What is matter made up of?
Particles
What are the smallest particles called?
Atoms
What are atoms?
The smallest building blocks from which all substances are made
What shape are atoms?
They are hard spheres
What do atoms usually form?
They are rarely on their own and they cluster together to form molecules
What are The 5 principles of Daltons atomic theory of matter?
1) all matter is made up of tiny, hard, invisible particles called atoms
2) substances made up of one type of atom are called elements
3) the atoms of different elements can be distinguished by their different masses
4) atoms can combine to form new substances called molecules
5) atoms are not created or destroyed in a chemical change
In a pure substance, what are molecules like?
Molecules all have the same number of atoms and are identical in size and shape
When a chemical change occurs, what happens to the atoms?
They rearrange to form different combinations of atoms
What happens if atoms rearrange to form a new substance with a different colour?
A permanent colour change has occurred
What happens if atoms rearrange to form a gas?
You will see bubbles, smoke or smell new odour
What happens if atoms rearrange to form a solid?
A precipitate may occur
In a chemical change can the atoms be created or destroyed?
No they are never created or destroyed
What are the starting substances known as in a chemical reaction?
Reactants
What are the substances that are formed in chemical reactions.
Products
What do reactants rearrange to form?
Products
How are atoms in molecules and lattices held together?
They are held together by chemical bonds that store energy
What are spontaneous reactions?
They are reactions that proceed by themselves
What are the two types of spontaneous reactions?
First can obtain enough energy from the surroundings to start and continue
The other needs a kick start from an external energy supply but can then continue with the reaction
What are non-spontaneous reactions?
Require and energy to be constantly added to it otherwise the reaction will stop
Why do scientists use chemical equations?
Because it is clearer, faster and easier
What replaces an equal sign in a reaction?
An arrow, there is no equal sign. The arrow means that the reactants have become the products
What s the simplest was to write a chemical equation?
By using chemical names:
Hydrochloric acid (HCL) + Sodium Chloride (NaOH)
A word equation looks like this:
Hydrochloric acid + Sodium Hydroxide -> Sodium Chloride + Water
What is a chemical equations?
Chemical name is now resolved with chemical formula
HCl + NaOH -> NaCl + H2O
What is corrosion?
When metal reacts with oxygen
Most common type of corrosion is rust
What makes some metals more likely to corrode?
Their chemical properties
What is rusting?
The name giving to the corrosion of iron
Iron needs to react with oxygen or water to produce orange-brown compound iron (iii) oxide (Fe2O3)
How can you prevent rusting?
Coating, galvanising and alloying
Why do we using costing?
It is cheapest and simplest way to protect iron
Coating forms a barrier between iron and oxygen
What happens if the barrier is removed in coating?
If coating is scratched or cracked the the barrier is removed and rusting will occur
What do we use to coat iron?
Paint, plastic or other metals like chromium
What is galvanising?
If iron is coated with zinc, it is good because even if it is scratched or cracked it will still protect
What does zinc react easily with?
Oxygen but even when it is scratched, the zinc reacts with oxygen not iron
What is iron is mixed with other metals?
The chemical and physical properties change. These mixtures are known as alloys
Why is iron never used in its pure form?
Because it is too soft and undergoes corrosion quickly
What is stainless steel made up of?
90% iron
10% chromium
