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Question 1

What are atoms?

Answer 1

Smallest part of an element that can exist. All substances are made out of atoms.

Question 2

What are atoms represented by?

Answer 2

Chemical symbols, (e.g. O represents an atom of oxygen).

Question 3

How many elements are there?

Answer 3

About 100 different elements.

Question 4

What are compounds?

Answer 4

Contain 2 or more elements chemically combined in fixed proportions.
They are formed from elements by chemical reactions.

Question 5

What do chemical reactions involve usually?

Answer 5

Always - formation of one or more new substances.
Usually - detectable energy change.(as in heat is taken in / given off?)

Question 6

What are mixtures?

Answer 6

Consists of two or more elements or compounds not chemically combined together.
The chemical properties of each substance in the mixture is unchanged.

Question 7

How to separate mixtures? (give examples)

Answer 7

By physical processes such as filtration, crystallisation, simple distillation, fractional distillation and chromatography.

Question 8

What are the 2 key points about the physical processes used to separate mixtures?

Answer 8

1) They do not involve chemical reactions.
2) No new substances are made.

Question 9

Relative (mass) of protons?

Answer 9

1.

Question 10

Relative (mass) of neutrons?

Answer 10

1.

Question 11

Relative (mass) of electrons?

Answer 11

Very small (2000x smaller), almost (0).

Question 12

Relative (charge) of protons? Electrons?neutrons?

Answer 12

Protons - (+1)
Neutrons - (0)
Electrons - (-1)

Question 13

What determines the size of an atom?

Answer 13

What element it is.

Question 14

Radius of an atom?

Answer 14

Around 0.1nm.

Question 15

What is an ion?

Answer 15

An electrically charged particle formed when an atom/ molecule gains or looses electrons.

Question 16

Which subatomic particle determines the element? (The quantity of that particle)

Answer 16

The number of protons.

Question 17

Atomic number?

Answer 17

Number of protons and number of electrons.

Question 18

Mass number?

Answer 18

Number of protons + neutrons (combined).

Mass number- atomic number = number of neutrons.

Question 19

What’s a mixture?

Answer 19

2/ more different types of substances that aren’t chemically joined.

Question 20

What are solutions?

Answer 20

What is formed when a solute dissolves in a solvent.

Question 21

What is filtration used for?

Answer 21

To separate INSOLUBLE solids from liquids.

Question 22

How to carry out filtration?

Answer 22

• Use filter paper that has lots of small holes that allow water to pass through but not the solids.
• Place filter paper in a filter funnel to pour mixture through it and leave the solids behind on the paper.

Question 23

What do we use evaporation and crystallisation for?

Answer 23

To separate a soluble solid from a liquid in a solution.

Question 24

How to carry out evaporation?

Answer 24

• Put solution in a crucible/ evaporating dish.
• Place dish on a tripod.
• Place Bunsen burner underneath the dish, so the flame heats up the solution and the solvent starts to evaporate.
• As the solvent starts to evaporate, the remaining solution starts getting more concentrated and after a while crystals will start to form.
• Eventually all of the solvent will disappear, leaving us with dry crystals of the solid.

Question 25

Pros and cons of evaporation?

Answer 25

Pro- its quick and easy. Cons- may break down solids into something else if the solids are susceptible to thermal decomposition.

Question 26

What do we use crystallisation for instead of evaporation?

Answer 26

Separating the SOLUBLE solids which are susceptible to thermal decomposition from the solvents. It is slower.

Question 27

How do we carry out crystallisation?

Answer 27

-Gently heat solution (place in an evaporating dish) by placing it in a water bath. -When some of the solvent starts to evaporate, we start to see some crystals. - When we start to see some crystals we stop heating our solution and leave to COOL. - As the solution cools, more crystals start to form. - Filter the remains crystals from the solution using filter paper and a funnel. -Dry crystals by leaving somewhere warm/ in a drying oven.

Question 28

Why do more crystals start to form as we leave the solution to cool during crystallisation?

Answer 28

Because solids are less soluble at colder temperatures.

Question 29

What’s simple distillation used for?

Answer 29

Separating a liquid from a solution.

Question 30

What’s fractional distillation used for?

Answer 30

Separating mixtures of liquids”?.

Question 31

Safety precautions of reacting alkali metals?

Answer 31

- use a saftey screen - wear goggles - use a small piece of metal

Question 32

What happens when lithium reacts with water?

Answer 32

- fizzes as hydrogen gas is given off - moves quickly and the surface and floats because it has low density

Question 33

What happens when sodium reacts with water?

Answer 33

- melts into a ball and moves around much quicker and faster than lithium - it floats - hydrogen gas is given off

Question 34

What happens when potassium is reacted with water?

Answer 34

- reaction is very vigorous - lots of heat by reaction given off ignites the hydrogen gas which results in a burning with a lilac flame - immediate and vigorous

Question 35

What happens to rubidium when it’s reacted with water?

Answer 35

- dissapers instantly - burns violently

Question 36

What reactions is the reactivity series used for?

Answer 36

- metals reacting with water and dilute acids (more reactive metals react more vigorously) - displacement reactions - extracting metals from their ores