Chemical Reactions Flashcards
What is a chemical reaction?
Two or more substances react chemically making a new product.
State the 4 signs of a chemical reaction.
colour change
gas produced
solid formed
energy (temperature) change
What is physical change?
when a substance changes without making a new product
Give three examples of chemical reactions.
frying an egg / making toast / candle burning / turkey cooking / burning wood in a fire / making steel from iron ore
Give three examples of physical changes.
melting ice / dissolving sugar / water boiling / water evaporating / freezing water
In a word equation, what name is given to the chemicals we start with?
reactants
In a word equation, what name is given to the new substances formed?
products
What should your word equation never include?
an equals sign ( = )
Write the following reaction as a word equation:
carbon burns in oxygen producing carbon dioxide
carbon + oxygen —> carbon dioxide
Write the following reaction as a word equation:
sodium chloride is formed when chlorine gas reacts with sodium
sodium + chlorine —> sodium chloride
Write the following reaction as a word equation:
magnesium burns in oxygen to produce magnesium oxide
magnesium + oxygen —> magnesium oxide
In the chemical formula:
4O2
What does the large 4 and small 2 indicate?
large 4: number of molecules
small 2: number of atoms
How many atoms are there in:
CH4
1 x C
4 x H
Total: 5 atoms
How many atoms are there in:
C2H6O
2 x C
6 x H
1 x O
Total: 9 atoms
How many atoms are there in:
Na2CO3
2 x Na
1 x C
3 x O
Total: 6 atoms
How many atoms are there in:
3 Na2CO3
3 lots of 2 x Na = 6 Na
3 lots of 1 x C = 3 C
3 lots of 3 x O = 9 O
Total: 18 atoms
What is an element?
a substance made of only one type of atom
What is a compound?
a substance made of two or more elements joined together chemically
What is a mixture?
two or more substances that are not joined chemically
Element, compound or mixture?
compound
Element, compound or mixture?
element
Element, compound or mixture?
mixture
Explain how the following represents a mixture:
The ‘blue atoms’ (an elements) are not chemically joined to the molecules of the compound (red and light blue atoms).
This is a mixture of an element and a compound.
Explains what happens when sugar dissolves in water.
sugar molecules fill the spaces between the water molecules
What does the term ‘solute’ mean?
substance that is dissolved
OR
substance added to a solvent to make a solution
What does the term ‘solvent’ mean?
the substance that dissolves the solute
OR
substance to which a solute is added to make a solution
What does the term ‘solution’ mean?
a solute dissolved in a solvent
State three ways in which the rate of dissolving can be increased.
- stirring the solution
- increasing temperature of solvent
- decreasing particle size
What always happens during a chemical reaction?
a new substance is always formed
State what is meant by the term ‘rate of reaction’?
how quickly a reactant is used up
OR
how quickly a product is formed
State three ways the rate of a reaction can be increased.
- increase concentration
- increase temperature
- decrease particle size
What is a catalyst?
a substance that speeds up a reaction but is not used up
