Matter

Question 1

What is chemistry?

Answer 1

The branch of science concerned with the substances which compose matter, the investigation of their properties and reactions and the use of reactions to form new substances

Question 2

What is matter?

Answer 2

The physical material of the universe and has mass and occupies space

Question 3

What is a mixture?

Answer 3

A combination of two or more substances in which each retains its own chemical identity and can be separated from each other

Question 4

What is the difference between heterogenous and homogenous mixtures

Answer 4

• homogenous mixtures are uniform throughout whereas,

- heterogenous mixtures does not have the same composition, properties and appearance throughout

Question 5

What is a pure substance?

Answer 5

Matter that has distinct properties and a composition that doesn’t vary from sample to sample eg. salt

Question 6

Define the states of matter

Answer 6

• solids have a definite shape and a definite volume
• liquids have definite volume but no specific shape
• gases have neither

Question 7

What are physical changes?

Answer 7

Observed without changing a substance into another substance eg. volume etc.

Question 8

What are chemical changes?

Answer 8

Observed when a substance is changed to another eg. during combustion etc

Question 9

What is a chemical reaction?

Answer 9

A process in which atoms of the same or different elements rearrange themselves to form a new substance

Question 10

Tell me about compounds

Answer 10

they can be broken down into elemental particles

Question 11

What is distillation?

Answer 11

Separation of a homogenous mixture by boiling point

Question 12

What does filtration do?

Answer 12

Separates solid substances from liquids and solutions

Question 13

Define mass

Answer 13

A measure of the amount of material in an object. The SI base unit of mass is the kg

Question 14

Convert degrees C to K

Answer 14

add 273.15K

Question 15

Define energy

Answer 15

The ability to do work

Question 16

What is kinetic energy

Answer 16

Energy of motion and potential energy is stored energy

Question 17

Compare exact and inexact numbers

Answer 17

• exact: counted/given by definition

- inexact: measured and depend on how they are determined

Question 18

What is precision

Answer 18

A measure of how closely individual measurements agree with one another

Question 19

What is accuracy

Answer 19

How closely individual measurements agree with the correct or ‘true’ value

Question 20

Name the atomic theory

Answer 20

1. Each elements is composed atoms
2. All atoms of a given elect are identical but atoms of one element are different from the atoms of all other elements
3. Atoms of one element cannot be changed into those of another by reactions and can’t be created or destroyed in those chemical reactions
4. Compounds are formed when more than one element’s atoms combine. The compounds always have the same relative number and kind of atoms

Question 21

Name 2 of Dalton’s laws

Answer 21

1. Matter cannot be created or destroyed
2. If two elements, A and B, form more than one compound, the masses of B that combine with a given mass A are in the ratio of small whole numbers (law of multiple proportions)

Question 22

How were subatomic molecules discovered

Answer 22

A ray of fluorescent negatively charged particles from cathode tubes are deflected by a magnet - charge was measured by charge/mass ratio using a Millikin’s Oil drop

Question 23

Define radioactivity

Answer 23

Spontaneous emission of high-energy radiation by an atom

Question 24

What types of particles are there?

Answer 24

alpha - positive
beta - negative
gamma - rays that have no charge

Question 25

What is the structure of the atom

Answer 25

- originally the plum pudding theory with a positive sphere and negative electrons dotted around in it - now when alpha particles were fired at gold, they scattered at different angles -> electrons on the outside and condensed positivity in the centre

Question 26

What are isotopes?

Answer 26

Atoms of the same element (same proton number) with different masses (neutrons)

Question 27

What is the atomic weight?

Answer 27

An average mass of an element that is found using all isotopes of an element weighted by their relative abundances relative to that of carbon 12 [ie. (75/100 of 55u) + (25/100 of 50u) = atomic weight of 53.75u]

Question 28

How is atomic weight measured?

Answer 28

Using a mass spectrometer you can identify the mass and relative abundances of the isotopes

Question 29

How is the periodic table arranged?

Answer 29

Arranged in periods = rows based on increasing atomic number | columns = groups

Question 30

List the seven diatomic molecules

Answer 30

Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine and iodine

Question 31

Define empirical formula

Answer 31

Lowest whole-number ratio of atoms of each element in a compound

Question 32

What is the molecular formula

Answer 32

Exact number of atoms of each element in a compound

Question 33

What is a structural formula

Answer 33

Formula that shows the order in which atoms are attached (no 3-D shape)

Question 34

What is an ion?

Answer 34

An atom that has lost or gained electrons (+ve ions are cations and -ve ions are anions) Polyatomic ions are a group of atoms that gain or lose electrons

Question 35

Define radioactivity

Answer 35

Spontaneous emission of high energy radiation by an atom alpha particles are positive beta are negative and gamma rays are nothing

Question 36

What was the initial atom (Circa) model like

Answer 36

plum pudding (ball with positive throughout and negative particles embedded around) firing of alpha particles at a thin gold foil found that some were deflected at large angles