AS and Periodic table Flashcards
What is meant by an atom?
An atom is the smallest part of an element that can exist.
What is meant by an element?
A substance that consists of only one type of atom.
What is meant by a compound?
A substance composed of two or more different elements chemically bonded together in fixed proportions.
What is meant by a mixture?
Two or more substances not chemically bonded together.
What is meant by a molecule?
2 or more different or same elements chemically bonded together.
Describe the properties of compounds in comparison to they elements it’s made from?
- Properties of compounds are different to properties of the elements they are made from.
Describe the properties of mixtures in comparison to the elements they are made from.
The properties of a mixture are the same as that of the elements they are made from. The properties are unchanged.
How can compounds be separated?
Through chemical reactions
How can mixtures be separated?
Through physical separation processes
How are compounds formed?
From chemical reactions.
What 2 things do chemical reactions always involve
- The formation of new substances
- A detectable energy change
What is filtration used to separate?
Insoluble solids from liquids.
eg X(s) from Y(l)
Summarise the process of filtration
- Place filter paper in filter funnel
- Put filter paper and funnel in a conical flask
- Pour the mixture into the filter paper
- The filter paper contains pores that allow liquid to pass through
- The insoluble solid will remain in the filter paper as it can’t pass through the pores, this is called the residue.
- The liquid will pass through the filter paper pores into the conical flask, and this is called the filtrate.
Give an example of filtration:
Filtering rock from water
What is crystallisation used to separate?
Soluble solids from liquids.
eg X(aq) from Y(l)
Summarise how crystallisation works:
- Leave solution in apparatus such as beaker for a few days.
- Water(or any liquid) evaporates
- Leaving behind crystals of solid substance that was once dissolved in the liquid.
OR
- Place solution in evaporating dish
- Heat evaporating dish GENTLY on Bunsen burner flame for water/liquid to evaporate
- This leaves behind crystals of the solid substance that was once dissolved in the liquid.
Why do scientists prefer evaporation over a few days rather than with a Bunsen burner during crystallisation?
- Because with a bunsen burner some chemicals break down due to heat (thermal decomposition).
- This effects the properties of the solid crystal produced (they will change).
Give an example of crystallisation:
Sodium chloride,NaCl, from salt water.
(salt from salt water to make salt crystals).
What is simple distillation used for?
To separate a dissolved solid from a liquid while also keeping the liquid.
What 2 main processes does simple distillation include, to obtain the liquid?
- Evaporation of liquid by heating.
- Condensation of liquid by cooling.
Describe the set-up for simple distillation.
- Flask connected to continuous glass tube
- Beaker at the end of continuous glass to collect liquid
- Glass tube is surrounded by a condenser that keeps the internal glass tube cold
- Cold water continuously runs in and out of the condenser
- Thermometer is also part of the apparatus
(Look at image).
Example of what simple distillation can be used for.
Production of drinking water from sea water.
A lot of energy is required from simple distillation so other techniques are used to do this.
Why is simple distillation not commonly used to provide drinking water from sea water?
A lot of energy is required from simple distillation so other techniques are used.
Explain the process of simple distillation.
- Solution is heated in a flask using a Bunsen burner until it boils.
- Liquid evaporates and turns into vapour.
- Vapour rises and as it rises the thermometer reading increases.
- Vapour passes into the continuous internal tube that is surrounded by a condenser.
- The condenser is cold bc tap water is continuously circulating around it.
- This causes the vapour to condense to a liquid
- The liquid is passed into the beaker
- And we are left with solid crystals in the flask and liquid in the beaker.