Chemical Changes & Structure: Rate Of Reactions Flashcards
What happens in ALL chemical reactions?
In every chemical reaction, a new substance is made.
When can you determine whether a chemical reaction has taken place?
You can only say a chemical reaction has taken place if:
- A new substance has formed
- One or more signs of a chemical reaction is evident.
What are the 4 signs of a chemical reaction?
• Signs of a chemical reaction include:
- Colour Change
- Gas being released/Bubbling and Fizzing (Effervescence)
- Solid being formed/Cloudiness formed(Precipitation)
- Energy/Temperature change
Name 3 chemical reactions we see in our day to day lives.
Some examples of everyday chemical reactions can include:
Burning toast, Milk going sour, Metal rusting, lighting a match.
Is water boiling a chemical reaction?
No, although it appears the water is releasing a gas it is just the water turning into a gas and will be reverted back to water after it cools.
if something is boiling, evaporating, freezing, melting, dissolving or condensing is that a chemical reaction?
Bonus: give 2 examples of chemical reactions similar to those listed above.
No, that is just warming something or making it smaller/larger it is NOT a chemical reaction it is a physical change.
Bonus: Burning and cooking are chemical reactions as they produce a new substance.
What is the speed of a reaction also known as?
The speed of a reaction is also known as the rate.
How can we speed up a reaction?
- Decrease particle size,
- increase temperature,
- increase Concentration,
- add a catalyst.
What is the concentration of a solution?
The concentration of a solution is a measure of how much solute is dissolved per unit of solvent.
what is the term used when no more solute can be dissolved in a solvent?
concentrated.
What is a catalyst?
Catalysts are substances which speed up chemical reactions but are not used up during the reaction.
why does decreasing particle size increase the rate of reaction?
Because when you decrease the particle size you increase the amount of surfaces a solvent can react with.
When looking at a graph following a reaction, when can we tell that the reaction has stopped?
once the line flattens out.
What can be said about the rate of a reaction over time? Identify the 3 key stages of the reaction.
Stage 1: The beggining, when the slope is steepest on a graph and the reaction is at its fastest.
Stage 2: The middle, when the slope is becoming less steep and the reaction is slowing down.
Stage 3: The end, once the line flattens and the reaction has stopped.
What is the formula to workout average rate?
Average rate = △Q/△t
change in quantity of reactant or product / Time taken for change
