Unit 1 chemistry

Question 1

Arrangement in a Solid?

Answer 1

Fixed and compact (all touching and must be organized/fixed in a line)

Question 2

Movement in a Solid?

Answer 2

Vibrating

Question 3

Energy Level in a Solid?

Answer 3

Low

Question 4

Arrangement in a Liquid?

Answer 4

Spaced (some are still touching each other but some aren’t and they are fairly close to each other)

Question 5

Movement in a Liquid?

Answer 5

Free (slow)

Question 6

Energy level in a liquid?

Answer 6

Medium

Question 7

Arrangement in a Gas?

Answer 7

Random (free)

Question 8

Movement in a Gas?

Answer 8

Free to move

Question 9

Energy level in a Gas?

Answer 9

High

Question 10

What is Diffusion?

Answer 10

It is the movement of particles from an area high concentration to an area low concentration

Question 11

What are the factors that affect diffusion and how do they affect it?

Answer 11

1) The concentration gradient (greater gradient, fast because particles get to collide with each other more often due to more particles present)

2) The Surface area (Greater SA, fast because theres more room in the walls of a container so particles can collide more often with walls)

3) Length of diffusion pathway (Greater pathway, SLOWER)

4) Higher temp (high temp, fast because more kinetic energy giving energy to particles)

Question 12

What causes diffusion?

Answer 12

In gasses and liquids, particles move freely which causes them to collide with each other (or with their container) and this makes them change directions which causes particles to spread around a place (or container)

Question 13

Explain the process of a solid to a liquid

Answer 13

This is called melting. You do this by heating a solid until it melts. When a solid is heated, particles gain kinetic energy which lets them vibrate faster. When the temperature is high enough, the vibration becomes strong enough to overcome forces of attraction in a solid which lets them move freely and slide past each other.

Question 14

Explain the process of liquid to solid

Answer 14

This is called freezing. You do this by cooling a liquid until it freezes. When a liquid is cooled, the particles lose their kinetic energy and when the temp is low enough, the particles don’t have any more energy to slide past each other, and the forces of attraction hold particles together.

Question 15

Explain the process of a liquid to a gas

Answer 15

This is called evaporation. You do this by heating a liquid until it boils. As it is heated, particles gain kinetic energy, and move further apart and forces of attraction in the liquid are then broken.

Question 16

Explain the process of a gas to a liquid

Answer 16

This is called condensation. You do this by cooling the gas until it condenses and when the gas is cooled, the particles lose kinetic energy, and forces of attraction between particles become weaker so they are now just close enough like a liquid

Question 17

Explain process of a solid to a gas

Answer 17

This is called sublimation. You do this by heating the solid until it sublimes and the solid particles gain energy which lets them vibrate faster and the forces of attraction are completely broken between the particles and become a gas

Question 18

What is an element?

Answer 18

A substance made up of only 1 type of atom

Question 19

What is a compound?

Answer 19

A substance made up of 2 or more DIFFERENT ELEMENTS which are chemically bonded

Question 20

What is a mixture?

Answer 20

A combination of 2 or more substances that are physically mixed but not chemically bonded (substance is classified as a mixture as long as the 2 substances are NOT chemically bonded so it doesn’t matter if they can dissolve with each other or not, if not chemically bonded then it is classified as a mixture)

Question 21

Mixtures vs compounds - Are the elements bonded to each other?

Answer 21

Mixture - No they aren’t
Compound - Yes they are

Question 22

Mixtures vs compounds - Properties?

Answer 22

Mixture - Elements still have their own properties
Compound - Has its own unique properties (different to elements)

Question 23

Mixtures vs compounds - Chemical formula?

Answer 23

Mixture - Atoms can be in any ratio
Compound - Formula is fixed with atoms in fixed ratios

Question 24

Mixtures vs compounds - Is it easy to separate elements and why?

Answer 24

Mixture - Easy to separate elements as atoms are not bonded together
Compound - Very hard to separate elements as atoms are bonded together

Question 25

Mixtures vs compounds - Methods used to produce them

Answer 25

Mixture - Filtration, distillation, chromatography, funnel, etc
Compound - Thermal decomposition, Electrical decomposition (electrolysis)

Question 26

What is simple distillation and how do you do it?

Answer 26

We use simple distillation to separate a liquid from a soluble solid in a solution (dissolved). The solution is heated and the liquid turns into vapour as it evaporates and rises. Vapour will pass through a condenser and it cools down later and condenses into a liquid which is then collected in a beaker. All the liquid is now evaporated and a solute is left. An example of this experiment is separating water from salt.

Question 27

What is fractional distillation and how do you do it?

Answer 27

We use fractional distillation to separate 2 or more liquids that are miscible (capable of being mixed together). The solution is heated to the temperature of the substance with the lowest boiling point and this causes one of the liquids to evaporate up through a fractionating column which is filled with lots of glass rods and is cold at the top (some of the other liquid with high boiling point will also evaporate but when it goes up, the cool temp cools it down so it wont go all the way up) and only the vapour with low boiling point will pass though a condenser where it cools down and condenses which turns into a liquid and is collected in a beaker and this leaves a substance or mixture behind. An example for this experiment is separating water from ethanol.

Question 28

What is filtration and how do you do it?

Answer 28

We use filtration to separate insoluble solids from liquids in a mixture (not dissolved). We first need to put a funnel with filter paper on top of a conical flask and then pour the substance into the funnel. The filter paper will only allow small liquid particles to pass the funnel and it will filter out large solid particles as they stay behind. The substance left behind is called the residue and the liquid is the filtrate. An example of this experiment is separating tea leaves from water.

Question 29

What is crystalization and how do you do it?

Answer 29

We use crystalization to separate a solute from a solvent (dissolved because it separates a solution). First place your substance into an evaporation dish and put it into a water bath to heat it. Some of the solvent will then evaporate and then crystals start to form in the solution so you then stop heating it and leave it to cool. More crystals will form because solids are less soluble at colder temperatures. Then filter out crystals using filtration method and then dry your crystals.

Question 30

What is chromatography and how do you do it (important) ?

Answer 30

We use chromatography to separate substances that have different solubilities (dissolved because it separates a solution). Take a piece of chromatography paper and use a pencil to draw a line near the bottom of the sheet called the baseline, then put a dot of sample of ink to pencil line. Then fill a beaker with a shallow amount of solvent. Place filter paper in beaker with solvent but don’t submerge the pencil line and ink. Also place a lid on top of beaker to stop solvent from evaporating. Solvent and ink will move up and the place where solvent stops moving is called a solvent front (draw a line). Different dyes that make up ink will also move up with solvent, the dyes move at different speeds which shows that each one is a different substance (dye with higher solubility moves faster) and this shows us components of the ink/dye.

Question 31

Chromatography - What is the stationary phase?

Answer 31

The paper because it doesn’t move

Question 32

Chromatography - What is the mobile phase?

Answer 32

The solvent because it moves

Question 33

How does a chromatogram (the pattern produced on paper) provide information about the composition of a mixture?

Answer 33

It shows the components of a mixture as they travel at different speeds so they get separated on the paper the amount of spots indicate the amount of compositions in the original mixture. The Rf value of the spots tells us how far the substance travels compared to the solvent.

Question 34

Chromatography - Why do samples move at different speeds during the experiment?

Answer 34

Different substances have different forces of attraction/affinities for the mobile and stationary phases. A substance with stronger attraction to mobile phase will move faster and closer with the solvent front whilst a substance with a weaker attraction to mobile phase but stronger attraction to stationary phase (paper) will move slower and further away from solvent front.

Question 35

What is an Rf value and what does it tell us and what is the formula?

Answer 35

The Rf value of the spots tells us how far the substance travels compared to the solvent.

Formula:
Distance travelled by substance
RF = ———————————————-
Distance travelled by solvent

Question 36

Where is the proton located, whats its charge, and whats its mass?

Answer 36

Location = Nucleus
Charge = 1+
Mass = 1

Question 37

Where is the neutron located, whats its charge, and whats its mass?

Answer 37

Location = Nucleus
Charge = Neutral (no charge)
Mass = 1

Question 38

Where is the electron located, whats its charge, and whats its mass?

Answer 38

Location = Electron shell
Charge = 1-
Mass = Negligible

Question 39

What does the mass number represent?

Answer 39

Represents number of protons + neutrons

Question 40

What does the atomic number represent?

Answer 40

Represents number of protons

Question 41

How do you find the number of protons, neutrons and electrons from an element on periodic table?

Answer 41

Proton = Atomic number
Electron = Atomic number
Neutron = Atomic mass - Atomic number

Question 42

Definitions of:
- Atom
- Molecule

Answer 42

• Atom = Smallest particle of element
• Molecule = A group of 2 or more ATOMS (can be same or different types) which are chemically bonded through covalent bonds

Question 43

What is an isotope?

Answer 43

2 or more atoms of the same element which have same atomic number but different mass numbers which means that they have same number of protons but different number of neutrons between the 2 atoms of same element

Question 44

What is the formula for average atomic mass for isotopic abundances?

Answer 44

Formula:
Ar of element =
(mass 1 x abundance%) + (mass 2 x abundance%) / 100

Question 45

Definition of abundance?

Answer 45

Relative amount of an element or isotope present in a sample. (usually as percentage)

Question 46

Definition of solute?

Answer 46

Substance that is dissolved in a solvent to form a solution (usually smaller amount than solvent and usually in all 3 states of matter)

Question 47

Definition of solvent?

Answer 47

Substance that dissolves a solute to form a solution (usually liquid and in larger amounts than a solute)

Question 48

Definition of solution?

Answer 48

A mixture of a solute dissolved in a solvent (MUST be dissolved to be called a solution, if they aren’t dissolved then it isn’t called a solution but its called a mixture but a solution is a type of mixture)

Question 49

Definition of soluble?

Answer 49

When a substance can dissolve in a solvent

Question 50

Definition of solubility?

Answer 50

Ability of a solute to dissolve in a solvent

Question 51

Definition of insoluble?

Answer 51

Substance that doesn’t dissolve in a solvent

Question 52

Definition of saturated?

Answer 52

When the solvent in a solution had already dissolved maximum amount of solute it can hold (in given temp) and if you add more solute, it wont dissolve

Question 53

Definition of unsaturated?

Answer 53

When solvent in solution CAN dissolve more solute because theres room for it

Question 54

Explain the dilution of coloured solutions

Answer 54

When you dilute a solution, the particles which give its colour start to spread out and as they start to spread, the colour becomes more lighter as the colours intensity starts to decrease because the concentration of the particles in each part of the liquid is lower. More you dilute, the weaker the colour intensity is so now theres a lighter colour.

Question 55

Definition of dilute/dilution?

Answer 55

It is when you reduce the concentration of a substance by adding more solvent. Example: adding more water to orange juice makes the colours concentration weaker and also makes taste weaker.

Question 56

Explain why a pure substance has a fixed melting and boiling point but a mixture doesn’t.

Answer 56

A mixture contains 2 or more different substances and because of this, mixtures don’t have a fixed melting or boiling points as their melting and boiling point temperatures depend on the proportions of each substance (pure substance is fixed because it is made up of 1 TYPE of particle so attractive forces is always same)

Question 57

What is meant by the term:
“solubility in g/per 100g of solvent” ?

Answer 57

It means the maximum mass of solute that is dissolved in 100g of solvent

Question 58

How do you calculate the solubility of a substance in 100g of solvent?

Answer 58

Use the formula:

Mass of solute
= ———————— x100
Mass of solvent

Question 59

What does Atomic mass mean?

Answer 59

The mass of a single atom (or isotope) which represent the mass of protons+neutrons

Question 60

What does Relative atomic mass mean?

Answer 60

It is the average mass of all different isotopes of the SAME element compared to 1/12th of the mass of a carbon-12 atom (Relative atomic mass specifically talks about only isotopes and carbon-12 is used as a comparison as it is ideal)

Question 61

How to investigate the solubility of a solid in water at a specific temperature

Answer 61

First, you must weigh and empty evaporating basin. Then pour some water into a tube and heat it up slightly above the target temperature (for example: target is 40 degrees so you heat it up to somewhere around 42 degrees). Then slowly add the solute while stirring the water, you will notice that the solute dissolves in water and keep adding solute until it no longer dissolves and excess solid (the undissolved solute) will be seen. Now allow the solution to cool exactly to the target temperature and then carefully pour only the solution into the basin and AVOID pouring the undissolved solid. Now weigh the basin with the solution and record the mass. Then heat the basin to evaporate the water, once dry heat it again to make sure ALL the water is evaporated. Then weigh the mass of the basin and solute. Then subtract the mass of basin and solute by the mass of the empty basin. This will give you the mass of the solute only. Then to find the mass of the water (solvent), subtract the mass of the solution and basin by the mass of the solute and the mass of the empty basin. This will give you the mass of the solvent. Now you have mass of solute and solvent, plug it into formula to find your answer.