Chemical Reactions Flashcards
What is meant by a “Physical change” ?
When two substances combine together but not chemically joined. They can be easily separated again.
What is meant by a”Chemical reaction” ?
When two substances combine and chemically join together to form a new substance. It is difficult to separate them back to thier original state.
Give 3 examples of a “Physical change”.
- Salt dissolving in water
- Ice cream melting
- Sand mixed into gravel
Give 3 examples of a “Chemical reaction”.
- Wood burning in oxygen to form carbon dioxide.
- Iron reacting with oxygen to form rust.
- Neutralising an acid with an alkali.
What are the common signs of a chemical reaction ?
- A permanent colour change.
- A gas released.
- Heat is taken in or released.
- A precipitate (a solid in a solution) forms.
- An odour is given off.
What is meant by the “Rate of reaction” ?
How quickly the reaction takes place.
What are the four ways to change the rate of a reaction?
- Change particle size.
- Change temperature.
- Change concentration.
- Use a Catalyst.
What is meant by a “Catalyst” ?
A chemical which increases the rate of a reaction, but is not used up in the process.
Which elements can be found in their “Native” (uncombined) state in the environment ?
- Gold
- Silver
- Platinum
What is meant by an “Ore” ?
A naturally occurring solid material from which a metal or valuable mineral can be extracted profitably.
What are the three methods for extracting an metal from its ore?
- Heating alone
- Heating with Carbon
- Electrolysis
What is meant by a “Reduction reaction” ?
A reaction in which oxygen is removed from a compound.
What is meant by an “Oxidation reaction” ?
A reaction in which oxygen is added to form a compound.
What is meant by “Electrolysis” ?
The use of electricity to separate a compound.
What is meant by “Corrosion” ?
The slow reaction of a pure metal in the environment to form a compound.
What is the corrosion of iron known as ?
Rusting
What two substances are required for rusting to occur ?
Water & oxygen
What is the chemical name for rust ?
Hydrated iron oxide
What substance can speed up the corrosion process?
Salt
What chemical used used to “test” for rust ?
Ferroxyl indicator - Colour chage from yellow to dark blue in the presence of rust.
What is meant by “Barrier protection” ?
A physical coating on a metal to prevent corrosion by blocking water & oxygen.
What are the 3 main types of “Barrier protection” ?
- Painting & greasing.
- Electroplating
- Galvanising
What is meant by “Electroplating” ?
The use of electricity to coat a metal in aother, less reactive metal.
What is meant by “Galvanising” ?
Dipping metal into molten zinc to apply a thin coating of zinc to the surface of the metal.
