C1-Atomic Structure

Question 1

What is an atom

Answer 1

Atoms are the smallest pieces of an element that can exist.

Question 2

How many elements have been dicovered

Answer 2

118 and each has its own chemical symbol

Question 3

What are compounds

Answer 3

Atoms of different elements can be combined together to create compounds. Compounds have formulae that are made by combing the chemical symbols of the elements that make them. Different combinations of atoms result in different compounds. A compound contains at least 2 different elements

Question 4

What are the key features of a chemical reaction

Answer 4

Compounds are broken up or formed. At least 1 new substance is created. They have a measurable energy change. No atoms are created or destroyed.

Question 5

What does a chemical equation show

Answer 5

Shows what is happening in a chemical reaction using symbols or words. The reactants (chemicals that are reacting) are on the left hand side, and the products (the chemicals that are forming) are on the right hand size

Question 6

What are mixtures?

Answer 6

Mixtures are made of 2 or more substances (elements or compounds) that haven’t been chemically combined. Mixtures can be separated. Their chemical properties don’t change because they have been mixed with another substance. Mixtures are common, e.g air is a mixture of gases such as carbon dioxide and oxygen

Question 7

Explain Chromotography

Answer 7

.Separates solutions with a number of different solutes (solids) in the solvent (liquid)

.Place a drop of the solution to be separated near the bottom of a piece of chromatography paper. Dip the very bottom of the paper into a suitable solvent. The solvent (liquid) moves up the paper and carries the solutes in the solution with it

.Different solutes move at different speeds so they separate on paper

Question 8

Explain filtration

Answer 8

.Separates mixtures of insoluble solids and liquids
.Done by pouring the mixture through filter paper
-the insoluble solid is trapped
-the liquid runs through the paper and is collected below

Question 9

Explain crystallisation

Answer 9

Separates solutions into their constituent (different )parts: disolved solids (solutes) and liquid (solvents).

.Heat the mixture so that the solvent evaporates. Eventually crystals ld the solute will form. We can collect the solvent by condensing it as it evaporates

Question 10

Explain simple distillation

Answer 10

Separates 2 liquids with different different boiling points

.The mixture is heated until the liquid with the lower boiling part starts to boil. The vapour released passes through a condenser where the gas cools back into a liquid

. A thermometer is used to make sure the highest boiling is not exceeded otherwise both liquids would boil and the process would not separate them

Question 11

Explain fractional distillation

Answer 11

Separates lots of liquids with different boiling points

The mixture is slowly heated until the liquid with the lowest boiling point boils and then condenses

Then the temperature is increased slowly to collect the other fractions through boiling and condensing

Question 12

Explain Thomson’s plum pudding model

Answer 12

In 1897, an English physicist called J.J Thompson discovered electrons

He modelled the atom as a plum pudding with is a ball of positive charge dough with negatively charged electrons mixed in with the ‘dough’

Question 13

Explain Rutherford’s nuclear model

Answer 13

.in 1909, Ernest Rutherford discovered that alpha particles could bounce back off atoms. He concluded that an atom’s mass is concentrated in the atom’s centre, this was called the “nucleus” and it contained positively charged particles called protons and negative electrons mixed in

Question 14

Explain the modern model

Answer 14

Niels Bohr discovered that electrons orbit the nucleus at fixed distances
In 1932 James Chadwick discovered that some particles in the nucleus have no charge at all. He called them neutrons

Question 15

What is the overall charge of an atom

Answer 15

Atoms have no overall charge as they cancel each other out

Question 16

What are the relative charges of the three subatomic particles?

Answer 16

Protons +1
Electrons -1
Neutrons 0

Question 17

What are the relative masses of the sub-atomic particles?

Answer 17

Relative mass of protons and neutrons = 1

Relative mass of electrons= 0.0005
Which gets rounded to zero

Question 18

What is the size of an atom

Answer 18

Atoms have an average radius of about 0.1nm

The nucleus of an atom is 10,000 times smaller than the atom

Question 19

Atomic number and mass number

Answer 19

The mass number of an atom also called relative mass is the total number of protons and neutrons in a nucleus. The atomic number of an atom is the number of protons in the atom