Atomic Structure

Question 1

Definition of an ! Atom ! (2marks)

Answer 1

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

(Atoms make elements ,elements make compounds, and then either element or compound make mixture)

Question 2

Definition of ! Compounds !

Answer 2

Compounds are the substances which are made when at least two different elements are combined together with covalent bonding.

Question 3

Atoms of different elements can be combined together to create __________.

Answer 3

Compounds

Question 4

What are the four key features of a chemical reaction?

Answer 4

1.Compounds are either broken up or formed.

2.At least 1 new substance is created

3.There’s a measurable energy change of it.

4.NO atoms are CREATED or DESTROYED in that process

Question 5

What are chemical equations?

Answer 5

A chemical equation shows what happens in a chemical reaction using symbols or words. The REACTANTS (the chemicals that are reacting) are on the LEFT -hand side, and the PRODUCTS (the chemicals that are forming) are on the RIGHT -hand side. (Sodium +oxygen —-> sodium oxide)

Question 6

What are symbol equations?

Answer 6

Symbol equations must be ‘balanced’ (have the same number of atoms of each element on each side of the equation). This is because atoms aren’t created or destroyed during chemical reactions. (4Na + O2 → 2Na2O- sodium oxide)

Question 7

What are ! Mixtures ! ?

Answer 7

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 in everyday life: like air is a mixture of oxygen ,nitrogen and carbon dioxide

Question 8

What is the use of Separation techniques?

Answer 8

We can normally separate mixtures into the elements or compounds that are found in them. We use physical processes to separate them. These processes don’t create new chemical substances (there are no chemical reactions).

Question 9

What is one of the separation technique-Chromatography?

Answer 9

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 (solids) in the solution with it.
Different solutes (solids) move at different speeds, so they separate on the paper.

Question 10

What is one of the separation technique-Filtration?

Answer 10

Separates mixtures of insoluble (can’t dissolve) 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 11

What is one of the separation technique-Crystallization?

Answer 11

Separates solutions into their constituent (different) parts: dissolved solids (solutes) and liquids (solvents).
Heat the mixture so that the solvent evaporates.
Eventually, crystals of the solute (dissolved solids) will form.
We can collect the solvent (liquid) by condensing it as it evaporates.

Question 12

Filtration is used to separate a solid from a __________.

Answer 12

Liquid

Question 13

Which of these techniques separates solutions with more than one type of dissolved solid (solute)?
1.Filtration
2.distillation
3.chromatography
4.crystallization

Answer 13

Chromatography !!!

Question 14

__________ are made up of 2 or more elements or compounds that haven’t been chemically combined together.

Answer 14

Mixtures

Question 15

What is one of the separation technique-Distillation?

Answer 15

Distillation is a special technique used to separate mixtures of liquids. It uses the different boiling points of liquids to separate them.

Question 16

Type of distillation- Simple distillation, what is it?

Answer 16

Separates 2 liquids with different boiling points.
The mixture is heated until the liquid with the lower boiling point starts to boil.
The vapour released passes through a condenser, where the gas cools back into a liquid.

Question 17

Type of distillation- Fractional distillation, what is it?

Answer 17

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 we increase temperature slowly to collect (boil then condense) the other fractions.

Question 18

Why is a thermometer used in simple distillation?

Answer 18

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

Question 19

Explain J.J Thomson’s plum pudding model.

Answer 19

In 1897, an English physicist called J. J. Thomson discovered electrons.
He modelled the atom as a ‘plum pudding’ - a ball of positive charge (dough), with negatively charged electrons (currants) mixed in with the ‘dough’.