chemistry Y8

Question 1

What is a mixture?

Answer 1

A mixture is two or more substances not chemically bonded.

Question 2

How is a mixture different from a compound?

Answer 2

Mixtures can be separated by physical methods and have the properties of the substances in them. No chemical change occurs when making a mixture.

Question 3

How can we use particle diagrams to represent mixtures?

Answer 3

Particle diagrams can visually represent the different substances in a mixture.

Question 4

How are solids separated out of mixtures?

Answer 4

Insoluble solids can be separated by filtering the mixture. The insoluble solid cannot pass through the filter paper but the liquid can.

Question 5

How can we separate a soluble solid from a liquid?

Answer 5

Evaporation can be used to separate a soluble solid from a liquid. The solution is heated so that the liquid evaporates, leaving the solid behind.

Question 6

What is chromatography?

Answer 6

Chromatography is used to separate mixtures of coloured or non-coloured substances that are soluble in the same solvent.

Question 7

How does chromatography work?

Answer 7

The substances in the mixture get separated because more soluble substances spread along the paper faster.

Question 8

What is the name of group 1 elements?

Answer 8

The Alkali Metals

Question 9

What is the name of Group 2 elements?

Answer 9

The Alkaline earth metals

Question 10

What is the name of Group 7 elements?

Answer 10

The Halogens

Question 11

What is the name of Group 0 elements?

Answer 11

The Noble Gases

Question 12

How are the elements in the periodic table currently arranged?

Answer 12

In order of atomic number

Question 13

What does the atomic number represent?

Answer 13

The number of protons in the nucleus

Question 14

How did Mendeleev organise the elements in the past?

Answer 14

• By increasing atomic mass
• In each column there were elements of similar properties

Question 15

How did Mendeleev include elements that hadn’t been discovered yet in his periodic table?

Answer 15

He left gaps for them and predicted their properties

Question 16

What do you observe when lithium reacts with water?

Answer 16

It fizzes

Question 17

What do you observe when sodium reacts with water?

Answer 17

It fizzes rapidly and you may see the melting of the metal

Question 18

What do you observe when potassium reacts with water?

Answer 18

It burns with lilac flame

Question 19

How does the reaction between alkali metals and water change as you go down the group?

Answer 19

The reaction becomes more vigorous

Question 20

What happens when you heat Iodine?

Answer 20

Iodine sublimation

Iodine is a grey-black solid at room temperature and pressure. If heated, it sublimes to form a purple iodine gas. Sublimation is the change of state from solid directly to gas on heating, without passing through the liquid phase.

Question 21

Describe what happens to the group 1 metals as you go down

Answer 21

Question 22

Tell me the 4 properties of group 1 metals

Answer 22

Group 1
elements have similar physical and chemical properties because they all have one electron in the outer shell of their atoms.

1.low density. The first three – lithium, sodium and potassium – are less dense than water and therefore float on water.
2.very soft. They are easily cut with a knife.
3.shiny when first cut, but tarnish rapidly in air.
4.low melting points. The
melting points
decrease as the atoms get bigger going down the group.

Question 23

How do group 7 molecules exist?

Answer 23

Group 7
elements exist as simple, diatomic (two-atom) molecules. Each molecule is made up of a pair of halogen atoms, linked by a single, covalent bond.

Question 24

Tell me some properties of the halogens

Answer 24

All are non metals
All are toxic
You will notice that, moving down Group 7, the element become darker in colour and change from gas to liquid to solid. This is because elements lower in the group have higher melting points

Question 25

Tell me about the noble gases- group 0

Answer 25

The Group 0 elements are all colourless gases.

All noble gases have low boiling points. Their boiling points increase as we move down the group.
Group 0 elements, very unreactive (however, it does form compounds with fluorine and oxygen).

Question 26

Uses o noble gases

Answer 26

Neon lights- advertising
Argon, insulation in double glazing
Helium or hot air balloons because lower density than air