Separating mixtures and evaporation

Section 1 from the Edexcel IGCSE Chemistry Specification - principles of chemistry

Fill in the blank

Temperature doesn't rise until all of the ____ substance has been melted.

pure

Fill in the blank

______ substances melt/boil over a range of temperatures.

impure

To separate salt and water (but the water still escapes), what can you do?

evaporation

To separate a salt-water solution to get both the salt and water back, what can you do?

simple distillation

What is the term given to when a liquid turns into a gas at the surface of the liquid?

hint - this can happen at any temperature, even when cold

evaporation

The rate of evaporation increases as....

Temperature increases

What is NaCl or sodium chloride?

Table salt

What is a risk of heating to dryness?

When it has lost a lot of solvent, the solution spits drops of very hot liquid

The safety flame is…

• Easily visible

• Not as hot

The blue flame is….

• Hotter than the safety flame

• Not easily visible

What is the boiling point of water?

100°C

What is the name of the technique used to separate substances dissolved in a mixture as different coloured dyes?

Chromatography

List 3 pure substances made up only one coloured dye.

Blue

Red

Yellow

Why do the pigments level up the paper at different speeds in paper chromatography?

• Some are more soluble

• Some stick to the paper more

"The chroma prefix in ''chromatography'' means black and white."

True or false?

False

"Water is a common solvent for paper chromatography."

True or false?

True

"Inks can be mixtures of different substances."

True or false?

True

"Chromatography separates solids from liquids."

True or false?

False

How many centimetres should you draw a pencil line from the chromatography paper?

2 cm

Why can't you draw the starting-point line on the chromatography paper in pen?

The ink will smudge and interfere with results

What is the name for the paper with the end result?

chromatogram

What is solute?

a substance (solid, liquid or gas) that dissolves in the solvent

What is a solvent?

a liquid that dissolves the solute or the substance the solute dissolves in

What is a solution?

formed when a solute completely dissolves in a solvent

What is meant by ‘soluble’?

if a solute dissolves in a solvent then it is soluble

What is meant by ‘insoluble’?

if a solute does not dissolve in a particular solvent then it is insoluble

What is distillation?

method used to separate a soluble solid from a liquid

What is diffusion?

when something travels from an area of a high concentration to an area of a lower concentration, until equilibrium is reached

"Diffusion is a passive process." 

What is meant by passive?

It doesn't require energy

What is the phrase given to a mixture that cannot take any more solute?

saturated solution

What are atoms?

particles that make up everything

What is a molecule?

more than one atom bonded together (can be the same type or different types)

What is an element?

a substance made up of only one TYPE of atom

What is a compound?

substances made up of two or more elements CHEMICALLY COMBINDED/BONDED/JOINED together (such as methane)

What is a mixture?

substances made up of two or more elements and/or compounds NOT chemically bonded together

water + sugar is an example of a...

Solution

water + milk is an example of a...

Colloid

water + chalk is an example of a...

Suspension

Fill in the gap:

"The _______ effect is when you can see the path of light through the mixture."

tyndall

What is the term given to mixtures that have a non-uniform distribution of components, leading to varying compositions in different parts of the mixture?

Heterogeneous

What term is given to the type of mixture that has a uniform composition throughout, meaning its components are indistinguishable and evenly distriputed?

Homogeneous

What is the melting point of ice?

0 degrees celcius

To separate water and sand...

Use filtration

To separate salt and water (where water escapes)...

Evaporate

What goes in the question mark?

Residue

True or false?

"Mixtures are not chemically joined."

True

True or false?

"Mixtures can be physically separated."

True

True or false?

"Milk is a suspension of different milk solids."

False