C3: Chemical Reactions Flashcards
All chemical reacitons do what 2 things?
- Make new substances
- Transfer energy to or from the surroundings.
What is a chemical reaction?
Where atoms are rearranged to make new substance.
Most chemical reacitons are not easily reversible. What does this mean?
At the end of a reaction it is very hard to get back what you started with.
When an ice cube melts is this a chemical reaciton or a physical change? Why?
Physical change
because it can be reversed e.g. changes of state can be reversed.
What is a catalyst?
A substance that can be added to a chemical reaction to speed it up.
They are not used up in the reaction.
What sort of things might you oberserve when a chemical reaction is happening?
Fizzing/Bangs
Smells
Temperature changes
Colour changes
When are chemical reactions not so useful?
Rusting is a chemical reaction.
This damages cars, boats and bridges.
The particles that make up all matter are called…
atoms
Is a physical change a chemical reaction?
No because it is reversible e.g. melting chocolate.
Chemical reactions are useful for making substances such as:
Medicines - paracetamol
Fabrics - polyester
Building materials - cement