Chemistry Flashcards
Elements are
Pure substances made from 1 type of atom
Compounds are
Pure substances made from 2 or more elements which are chemically joined together
Mixtures are
2 or more substances that are not chemically joined
What is an alloy
A mixture of 2 or more elements, one of which is always a metal
What are 4 signs of a chemical change
Colour change, energy change (heat, light or sound), gas (bubbles), precipitation (cloudy solid appears in a solution)
What chemical change always happens
Forms new substances
Chemical changes are usually ? to reverse
Very difficult or impossible
What is a physical change
When the appearance or form changes but no new substances are made
What is sodium chloride
Sodium+chlorine
What is the most reactive metal
Potassium
What is the least reactive metal
Platinum
What is combustion
Burning
How can you remember the first 5 most reactive metals
End in -ium
How can you remember the 4 least reactive metals
Used in jewelry
Most reactive metals are ? to extract from their compounds
Very hard
