Chemistry science junior cert

Question 1

What is matter?

Answer 1

Matter ​refers to anything that occupies space and has mass

Question 2

List the changes of state of matter?

Answer 2

Boiling and evaporating
● When a liquid is heated to its boiling point, particles gain energy to break away to form gas
● The boiling point is when a liquid changes into gas throughout the liquid
● Evaporating refers to when a liquid changes into gas
Diffusion
● The movement of particles from an area of high concentration to an area of lower concentration
Melting
● The melting point refers to the temperature at which a solid turns into a liquid
● From a solid to a liquid
Condensing
● When gas changes to liquid
Freezing
● When liquid changes into solid

Question 3

What is an element?

Answer 3

An ​element​ is a substance which cannot be split up into simpler substances by chemical means.
All the known elements are listed in the Periodic Table of Elements.

Question 4

What is a compound

Answer 4

A ​compound​ consists of two or more​ ​different elements combined together chemically.

Question 5

What is a mixture?

Answer 5

A ​mixture​ contains two or more substances mingling together but not chemically combined.

Question 6

What is filtration ?

Answer 6

Mixtures of a liquid and an insoluble solid can be separated using f​ iltration​. Eg. Sand and water
In this technique, the mixture is put into a funnel lined with filtration paper above a beaker.
The liquid passes through the small holes in the filtration paper and into the beaker, but the solid is left behind as it cannot pass through the holes.

Question 7

What is evaporation?

Answer 7

Mixtures of a soluble solid dissolved in a liquid can be separated using e​ vaporation​ if the liquid is not needed once the separation is complete.
Eg. Salt and water
In this technique, the mixture can be heated and the liquid is allowed to evaporate. This leaves behind the solid, sometimes in the form of crystals.

Question 8

What is distillation?

Answer 8

Mixtures of a soluble solid dissolved in a liquid or of two liquids that have different boiling points can be separated using ​distillation​ if both substances are to be kept.
Eg. Alcohol and water
In this technique, the mixture is heated to the lowest boiling point of the substances. The liquid becomes gas and passes into a ​Liebig condenser,​ where it is cooled and condensed back into liquid. It pours out the other end and into a beaker, leaving behind the other substance.

Question 9

What is chromatography?

Answer 9

Mixtures of different dyes in an ink can be separated using c​ hromatography.​ Eg. Black, water-soluble marker ink
In this technique, a strip of chromatography paper is left to partially hang in a beaker of water. There is a spot of ink just above the surface of the water. The water will be drawn up the paper and will drag the ink dyes up with it, separating them into clear colours which stop at different heights.

Question 10

Explain solutions and solute

Answer 10

A ​solute ​dissolves in a ​solvent​ to form a ​solution.
If one substance does not dissolve in another, it is i​ nsoluble.​
If one substance does dissolve in another, it is s​ oluble.​
A mixture of an insoluble substance in another substance is called a s​uspension
In general, the solubility of a substance increases as temperature increases.

Question 11

What is fuel?

Answer 11

A ​fuel ​is any substance which burns in oxygen to produce heat.

Question 12

What are fossil fuels?

Answer 12

A ​fossil fuel​ is a fuel that was formed from the compressed remains of plants and animals that lived millions of years ago.

Question 13

What are hydro carbons?

Answer 13

Hydrocarbons​ are compounds consisting of only Hydrogen and Carbon. They are often found in fossil fuels. When hydrocarbons are burned, Carbon dioxide and water are made.

Question 14

What is acid rain and the effects of acid rain?

Answer 14

Most rainwater is a weak carbonic acid, but when sulphur dioxide and nitrogen oxide mix with rain water they form a stronger acid that can cause damage.
How acid rain is formed:
Factories​ burn fossil fuels
Oxides of ​sulphur​ are released into the air They mix with oxygen to form Sulphur dioxide This mixes with rainwater to form Sulphuric acid

Effects of acid rain:
● The acid destroys lakes and kills their fish and plant life creating “dead lakes”
● Trees are harmed and killed ruining forests and natural habitats
● Limestone or Iron buildings and statues are corroded and attacked by the acid

Question 15

What are plactics?

Answer 15

Plastics ​are man made materials made from ​crude oil.

Question 16

What are monomers?

Answer 16

Simple hydrocarbons are isolated from the crude oil and many of these are produced during a process known as cracking. They are known as ​monomers.

Question 17

What are polymers?

Answer 17

Polymerisation ​is the process involving the joining together of many small molecules called
monomers to form a large molecule called a polymer.

Question 18

What are the environmental impacts of plastics?

Answer 18

Biodegradable plastics can be broken down by decomposers by our environment
However, most plastics are non biodegradable and this causes problems if they are not recycled properly.

Question 19

What is Electrolysis​?

Answer 19

Electrolysis​ is the production of chemical change by electricity and is used to separate water into Hydrogen and Oxygen.

Question 20

What is the process of water treatment?

Answer 20

Treatment Process
Drinking water needs to be treated so we don’t catch diseases.
1. Screening​ => removes leaves
2. Flocculating​ => small particles flock together and float to the bottom to be removed
3. Filtration​ => removes tiny particles and dirt
4. Chlorination​ => kills micro-organisms
5. Fluoridation​ => adds Fluoride to water to keep teeth healthy

Question 21

What are the advantages of hard water?

Answer 21

Benefits of Hard Water
The calcium is good for teeth and bones It has a nicer taste
It is good for brewing alcohol and tanning leather

Question 22

What are the disadvantages of hard water?

Answer 22

Disadvantages of Hard Water
Limescale builds up in pipes and kettles It wastes soap
It produces a scum

Question 23

What gases is the atmosphere made of?

Answer 23

The atmosphere contains a mixture of gases. It is: 78% Nitrogen
21% Oxygen
0.04% Carbon dioxide
1% Other gases

Question 24

What is neutralization? And give an example

Answer 24

Neutralisation​ occurs when an acid and a base balance out to create a neutral substance. A ​salt​ is formed during neutralisation when the hydrogen in an acid is replaced by a metal.
Acid + Base Salt + Water HCl + NaOH NaCl + H​2​O

Question 25

What is tritation?

Answer 25

A ​titration​ is used to find the exact amount of acid needed to neutralise an certain amount of base.