chem 🧪⚗️

Question 1

what are the states of matter

Answer 1

solids liquids and gases

Question 2

what is particle theory?

Answer 2

It is based on the idea that all substances are made up of extremely tiny particles.

The particles in the three different states of matter are arranged differently and have different types of movement and different energies.

Question 3

what are the different stages of changes in matter?

Answer 3

melting, boiling (evaporating), condensing and freezing.

Question 4

how are solids, liquids and gases different?

Answer 4

slg have different properties depending on how strongly particles are held together.

Question 5

solids vs liquids vs gases

Answer 5

solids: they have a fixed volume and shape.

liquids: have a fixed volume but not a definite shape. They take up the shape of the container.

gases: have no fixed volume or shape. Particles spread out in order to fill any container or space.

Question 6

why do s l g behave differently?

Answer 6

In substances, particles are constantly in motion. However, these movements differ according to the state of matter and according to the energy levels.

Question 7

energy according to s l g

Answer 7

solids: particles are held tightly together and although they rent free to move around, they vibrate on the spot because they still have some energy.

liquids: In liquids, particles are held tightly together, however they have more energy than solids which make them move around.

gases: In gases, particles are loose and have enough energy to move around and apart from eachother, constantly moving. Gas particles spread apart to keep moving

Question 8

how do substances change from one state to another?

Answer 8

solid->liquid->gas
This transition the addition of heat energy which is given to cells to break apart imf (inter molecular force) as the cells themselves move apart from eachother.

gas->liquid->solid
this requires the removal of heat energy. Particles move closer together and bond as liquid->solid.

Question 9

explain what happens during evaporation

Answer 9

the particles in liquid have different energy levels so some are moving faster than others. Those particles which move faster escape from the surface causing evaporation.

The rate of evaporation increases as external temperatures increase.

Question 10

what are some examples of unusual cases where substances dont follow the laws of particle theory?

Answer 10

superfluids: when liquids are cooled down to very low temperatures, they develop into a second liquid state called superfluid. Liquid helium at just above zero has “infinite fluidity” and will “climb out” of its container when left undisturbed.
plasma

plasma: can exist at temperatures of several thousands of degrees. An example of plasma is charged air produced by lightening. Like gas, a plasma does not have a definite shape or volume but its strong forces between particles give it strange properties such as electrical conductivity.

Question 11

what are elements

Answer 11

They are substances that cant be broken down into anything simpler because they are made of only one type of the same atom.

Question 12

What are molecules

Answer 12

Two or more atoms chemically bonded.

Both elements and compounds can be considered molecules.

Question 13

what are compounds

Answer 13

A substance made up of two or more types of atoms (elements)

Question 14

what are mixtures

Answer 14

a material made up of two or more different chemical substances which are NOT chemically bonded.

Question 15

what is diffusion

Answer 15

the random mixing and moving of particles in liquids and gases (generally from a region of higher concentration to a region of lower concentration)

Question 16

in which three states of matter are the particles moving the fastest

Answer 16

gases.

Question 17

what is paper chromatography?

Answer 17

a way of separating or identifying solutions or liquids that are mixed together.

Question 18

how can substances be identified through chromatography?

Answer 18

by calculating retention factor; this is the distance a substance has travelled up the filtered paper/ the distance travelled by the solvent.

As the solvent will always travel further, Rf will always be >1

Question 19

whats a simple way of checking the purity of solids and liquids?

Answer 19

using heat to find the temperature at which it boils or melts.

Question 20

an impure solid will have a _____ melting point than a pure solid

Answer 20

lower

Question 21

a liquid containing a dissolved solute will have a ______ boiling point than the pure solvent.

Answer 21

higher

Question 22

methods of purification

Answer 22

filtration, evaporation, filtration+evaporation, distillation, fractional distillation.

(refer to notebook to study the methods)

Question 23

what are factors of chemical changes?

Answer 23

in a chemical change, one or more substances are produced.

In many cases, an observable change is apparent; for example, change in colour or formation of gas.

Question 24

in chemical changes, can mass technically change?

Answer 24

no; according to the law of conservation of mass, mass cannot be created or destroyed

. Therefore if a change in mass is seen in a reaction, this would be due to the formation of gas which might have escaped.

Question 25

in chemical changes, what kind of change is involved most of the time?

Answer 25

energy change; energy is either released or gained and absorbed (exothermic, endothermic)

Some physical changes also undergo energy changes; for example water s->l->g vise versa

Question 26

what can most elements be classified as?

Answer 26

metal or non metal

Question 27

in a periodic table, how are metals arranged?

Answer 27

metals are on the left and middle, non metals are on the right.

Question 28

physical and chemical properties of metals

Answer 28

-Ductile; can be draw into a wire
-Good conductors of heat
-Good conductors of electricity
-high melting points
-shiny
-malleable; can be hammered into a shape
-sonorous; rings when struck

*anomalies:
-the alkali metals have a low melting point.
-Mercury has a low melting point

Question 29

physical and chemical properties of non metals

Answer 29

-brittle
-poor conductors of electricities
-poor conductors of heat
-dull
-low melting points

*anomalies:
-carbon in the form of graphite is a good conductor of electricity
-carbon and silicon have high melting points.

Question 30

how is an alloy formed

Answer 30

when metals are mixed with other elements.

Question 31

whats an example of a chemical reaction that can be reversed?

Answer 31

when hydrated blue copper sulfate crystals are heated, a white powder is formed and water is lost as a stream. If water is added to this white powder, hydrated blue copper sulfate is formed again.

Question 32

what are the three main subatomic particles?

Answer 32

protons, electrons and neutrons.

Question 33

how can the masses of subatomic particles be measured

Answer 33

using the relative scale. Their charges may also be compared in a similar way.

Question 34

the proton and neutrons have the ______ mass and protons and electrons have ________but opposite charges

Answer 34

same, equal

Question 35

where are protons, neutrons and electrons found in an atom?

Answer 35

protons and neutrons are found in the center of the atom in a cluster called the nucleus.

The electrons form a series of shells around the nucleus.

Question 36

what is the mass of the electron in comparison to protons and neutrons?

Answer 36

1/2000 of the masses of p and n

Question 37

what unit do scientists use to measure the number protons?

Answer 37

atomic number.

Question 38

what unit do scientists use to measure the number of particles in the nucleus?

Answer 38

nucleon number.

Question 39

what is atomic unit used for?

Answer 39

it is used to arrange the elements in the periodic table.

Question 40

what are isotopes?

Answer 40

Isotopes are atoms with the sane number of protons and electrons but different numbers of neutrons.

e.g Carbon 14 is an isotope of carbon, with 8 neutrons and 6 neutrons

Question 41

do the chemical properties of isotopes differ from the original atom?

Answer 41

no, as the chemical properties of atoms depend on the arrangement of electrons in their atoms

Question 42

how are electrons arranged in the structure of an atom?

Answer 42

they are arranged in shells around the nucleus.

Question 43

how many electrons can the shell nearest to the nucleus hold?

Answer 43

max. 2. The next one out from the nucleus can take up from 8.

Question 44

if in an oxygen atom, there are two electrons in the first shell and six are in the next shell, whats the arrangement

Answer 44

2,6

Question 45

what are the electrons in the outer shells that are involved in chemical bonding known as?

Answer 45

valency electrons.

Question 46

what is the electron arrangement in an atom called?

Answer 46

electric configuration.

Question 47

what increases, moving through a section or period of the periodic table? and what is this called

Answer 47

the electron number increases. This is called periodicity.

Question 48

elements that have similar electron configurations have ______

Answer 48

similar chemical properties

e.g lithium, sodium, potassium all have one electron in their outer shells. They are also group 1 elements which are highly reactive metals.

Question 49

why are helium, neon, argon and krypton so unreactive?

Answer 49

they all have 8 electrons in their outer shells or full outer shells

this means the atoms don’t lose or gain electrons easily.

Question 50

what is formed when one of the reacting atoms is a metal and the other is a non metal?

Answer 50

an ionic compound. it is made up of ions.

Question 51

ionic compounds have similar _______ and are quite different from the properties of substance made up of ______ and _______

Answer 51

physical properties

atoms

molecules

Question 52

how are ions formed?

Answer 52

through the gain and loss of electrons. Both metals and non metals try to achieve complete (filled) outer electron shells.

Question 53

when metals lose elctrons from their outer shells what is formed?

Answer 53

positive ions.

Question 54

what is formed when non-metals gain electrons in the outer shells?

Answer 54

negative ions.

Question 55

whats an example of ionic bonding?

Answer 55

sodium has 11 electrons arranged 2,8,1. chlorine is a non metal and has 17 electrons, arranged 2,8,7.

The sodium atom can achieve a full outer shell by losing an electron. The chlorine atom can achieve a full outer shell by gaining an electron. The sodium atom transfers the electron.

The sodium atom is no longer an atom, its an ion. The chlorine is also not an atom, its an ion. They are both no longer neutral.

The sodium atom has one less electron than the number of protons. It has a positive charge. Its written as NA^+ (u dont write the 1 but when its 1< u write)

the chlorine atom has 1 more electron than the total number of protons and becomes a negative ion.

Question 56

can metals transfer more than one electron to a non metal?

Answer 56

yes.

e.g magnesium combines with oxygen to form magnesium oxide. The magnesium (2,8,2) transfers two electrons to the oxygen atom (2,6)

Magnesium thus forms Mg+2 ion and oxygen forms O-2

Question 57

oxidation vs reduction

Answer 57

when in the process of forming an ionic compound, the atom that loses electrons is said to be oxidised.

the atom that gains electrons in reduced.