Chemistry Vocab

Question 1

Define melting point:

Answer 1

Temperature at which a substance changes from a solid to a liquid when heater or from a liquid to a solid when cooled.
A physical property, all parts of a pure substance will melt at the same temperature because pure substances have the same composition throughout.

Question 2

Define physical change:

Answer 2

A change in which no new substances are formed- like changes of state

Question 3

Define a physical property:

Answer 3

How a material behaves and responds to forces and energy, e.g hardness

Question 4

Define a pure substance:

Answer 4

1A single substance, with a fixed composition(the make up does not change), that does not have anything else mixed with it.
2.Is that same in all parts of a piece of the substance
3. Cannot be separated using physical methods (compounds)

Question 5

Define residue:

Answer 5

Material remaining in the filter after mixture has passed through it

Question 6

Define risk & risk assessment:

Answer 6

Risk: the chance of a hazard causing harm
Risk assessment: identification of the hazards of doing an experiment

Question 7

Define saturated solution:

Answer 7

Contains the maximum amount of solute that can dissolve in that amount of solvent at that temperature

Question 8

A sentence linking solute, solution, solvent

Answer 8

a solute dissolved in a solvent to make a solution

Question 9

What is chromatography used for and why does it work?

Answer 9

Chromatography is used to find out which coloured compounds a mixture contains. It works because different compounds dissolve better in a solvent than others. When a solvent moves along a strip of paper it carries the substances at different speeds, so they are separated.

Question 10

Stationary phase of paper chromatography:

Answer 10

The surface through which the solvent and dissolved substances move in (PAPER)

Question 11

The mobile phase of paper chromatography:

Answer 11

The solvent that moved along the paper carrying the dissolved samples with it

Question 12

Define chromatogram:

Answer 12

The piece of paper showing the results of carrying out chromatography on substances

Question 13

Define Rf value:

Answer 13

The ratio of the distance traveller by the solute on a chromatography to the distance traveller by the solvent under the same conditions.
= distance travelled by substance/distance travelled by solvent

Question 14

Define distillation:

Answer 14

The process of separating a liquid from a mixture by evaporating the liquid and then condensing it (so it can be collected)

Question 15

Define fractional distillation:

Answer 15

A method of separating a mixture of liquids with different boiling points into individual components (fractions)

Question 16

Define a mixture:

Answer 16

A mixture contains elements and or components that are not chemically joined together. You can use physical processes to separate them into different substances.
They do not have the same composition throughout e.g - air is a mixture of gases which is constantly changing as we breathe
Mixtures melt at a range of temperatures and not all parts melt at the same time

Question 17

Define a still:

Answer 17

The apparatus used to carry out distillation or fractional distillation

Question 18

Define an aquifer:

Answer 18

Underground layer of rock containing groundwater, which can be extracted using a wall or pump

Question 19

Define chemical analysis:

Answer 19

Using chemical reactions or sensitive machines to identify and measure substances in a sample

Question 20

In what order is water treated?(3)

Answer 20

1 filtration
Sedimentation
Chlorination

Question 21

Define desalination

Answer 21

Produces fresh drinking water by separating the water from the salts in salty water

Question 22

Define precipitate:

Answer 22

Insoluble substance formed when two soluble substances react together

Question 23

Define chlorination: (water treatment)

Answer 23

The process of adding chlorine to a water to kill harmful microorganisms and bacteria

Question 24

Define filtration(water treatment):

Answer 24

Smaller insoluble particles are removed using sand and gravel beds

Question 25

Define sedimentation (water treatment) :

Answer 25

The process in which rock grains and insoluble particles sink and settle

Question 26

Separating substances: crystallisation

Answer 26

Used to separate a solute from a solvent in a solution, evaporates the solvent to leave behind the solute. The slower the crystals cool, the longer they have to for an ordered patttern so the larger they are

Question 27

Separating substances:Filtration

Answer 27

Is used to separate mixtures, let smaller pieces/liquids but trap bigger or insoluble substances.