Principles of chemistry

Question 1

What are particles like in a solid?

Answer 1

Particles vibrate around a fixed position.
A strong force of attraction between each particle and they are close together.

Question 2

What are particles in a liquid like?

Answer 2

Particles are close together but can move in any direction. They won’t keep a fixed shape like solids do.

Question 3

What are particles in a gas like?

Answer 3

Particles are very far apart and move quickly in all directions. They often collide with each other and because they are far apart they can be easily squashed. Particles in a gas have the most energy.

Question 4

Changes of state:

Answer 4

Solid and liquid - melting and freezing
Liquid and gas - evaporation and condensation
Gas and solid - deposition and sublimation

Question 5

What is diffusion?

Answer 5

When something travels from an area of high concentration to an area of low concentration.

Question 6

Soluble and insoluble

Answer 6

If a substance can be dissolved it is soluble and if not it is insoluble.

Question 7

What is a mixture that cannot take any more solute called?

Answer 7

A saturated mixture

Question 8

What does solubility mean

Answer 8

How much can be dissolved and is measured in grams per 100g of solvent

Question 9

Compounds

Answer 9

Two or more different elements chemically bonded together

Question 10

Mixture

Answer 10

A compound made up of two or more chemical components that are not chemically linked

Question 11

Element

Answer 11

A simple chemical substance that consists of atoms of only one type and cannot be split by chemical means into a simpler substance

Question 12

Molecule

Answer 12

Two or more atoms connected by chemical bonds, the atoms can be different or the same

Question 13

When can you use distillation and for what?

Answer 13

You can use distillation to separate any liquids with different boiling points such as the distillation of crude oil or ethanol and water.

Question 14

Method of distillation

Answer 14

This apparatus can be used to separate water and ethanol because they have different boiling points. The ethanol will evaporate first, turn back into a liquid in the condenser, and collect in the beaker. The water remains in the round flask, as long as the temperature does not exceed the water’s boiling point. This method can be used to separate any liquids with different boiling points such as the fractional distillation of crude oilD.

Question 15

When is filtration used and how

Answer 15

Filtration is used to separate an insoluble solid from a liquid
If the product of a reaction is an insoluble solid, you can use filtration to separate it out from the liquid reaction mixture.
It can be used in purification as well - eg in solid impurities
You put some filter paper into a funnel and pour the mixture. The liquid part runs through the paper, leaving behind the residue.

Question 16

When is crystallisation used and how

Answer 16

Crystallisation separates a soluble solid from a solution
Method:
You pour the solution into an evaporation dish and gently heat the solution. Some of the water will evaporate and the solution will get more concentrated,
Once some of the water has evaporated, or when you see crystals start to form (the point of crystallisation), remove the dish from the heat and leave the solution to cool.
The salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution,
Filter the crystals out of the solution, and leave them in a warm place to dry - or use a drying oven or desiccator.