GRADE 9 SCIENCE EXAM Flashcards
what is the charge, weight and where are they located? protons, neutrons, electrons
who discovered them
PROTONS -positive -Located inside the nucleus - 1amu - Henry Mosely, proved they are in the nucleus NEUTRONS -no charge -located inside the nucleus -1amu - Chadwick discovered them ELECTRONS -negative -located around the nucleus -0amu - J.J Thompson
what is matter
- anything that has mass and weighs something
- takes up volume
- mass is constant
- mass and weight are not the same thing
who is Empedocles
- philosopher
- proposed that matter was made of 4 elements
1. air 2. earth 3. fire 4. water - he thought if you mixed these elements together in different amounts, you would make different substances
who is Democritus
- suggested that matter was made of tiny particles, which couldn’t be broken down any further
- called these particles atoms: from the Greek word atmos meaning indivisible
- thought different types of matter were made of different types of atoms
- at the time, Democritus’ idea was not accepted because Aristotle did not think it was true.
who is Aristotle
- came up with the theory called transmutation- one form of matter could be turned into another.
- you could turn something worthless into lead, into something valuable like gold. this paved the way for alchemists
what are alchemists
-first people to perform experiments
they had three main goals:
-change bas metals into gold
-find a substance for eternal life
-produce a universal solvent (will dissolve anything)
- none of these goals were reached, however they are important to history because:
-they discovered many elements and their property, including chemical symbols
- they invented many lab tools we still use today
- they actually performed these experiments
define ductility
-ability to be shaped or stretched into a wire without breaking
define malleability
ability to be hammered pressed or rolled into thin plates
define conductivity
how easily heat and electricity can pass through a substance
define lustre
how shiny a material is
metals
- make up about 75% of the P.T
- located all over the P.T, but are concentrated on the left side
- are shiny, conduct heat, can make wires or be stretched into sheets
non-metals
- make up about 15% of the P.T
- found on the far right side of the P.T
- are poor conductors, not shiny, are brittle and not ductile
define metalloids
- make up about 6% of the elements
- located on the “staircase” of the P.T
- have properties of both metals and non-metals
atomic mass
- atomic weight rounded to the nearest whole number
- average mass of an element
- total number of protons and neutrons in the nucleus
atomic number
- tells us how many protons and electrons are in the nucleus
-the P.T the atomic number is the number that identifies the element
elements are arranged from left to right, top to bottom in order of their atomic number
how to find the # of neutrons in an atom
- subtract the number of protons (atomic number) from the atomic mass
who is Mendeleev
- known as the father of the P.T
- arranged the 63 known elements in order of their atomic mass and saw the repeating patterns of properties
- Mendeleev left spaces for undiscovered elements, correctly predicted where new elements would be found
- his table summarized the structure and property of the elements
- the problem with his table, occurs when atoms are arranged by mass only properties did not always match up when atomic mass was used.
- by matching properties, he was able to place iodine and tellurium in their proper places.
what is a period
- vertical rows with numbering 1-7 from top to bottom
what is a family/group
- horizontal columns labeled 1-18.
- there are 6 families
- in each column the elements have similar chemical properties
family/- hydrogen
- family of its own
- has one valence electron
- reacts vigorously
- cannot exist at a single atom (too reactive) but as a molecule H2.
family-alkali metals
- reacts vigorously with many other substances
- larger the alkali metal, the more reactive
- located at group 1
family-alkali earth metals
- reacts fairly vigorously
- the larger the metal, the more reactive
- located at group 2
family-chalcogens
- quite reactive, but not as much as halogens
* located at group 16
family-halogens
- react very vigorously with nearly everything
- the least reactive is still corrosive
- larger the atom, less reactive
- located at group 17
family-noble gases
- are unreactive (inert)
* located at group 18
what are Bohr diagrams
- each orbit can hold a specific amount of electrons
first shell= 2 electrons
second shell and third shell= 8 electrons - electrons on the outer shell are known as valence electrons
chemical reactivity
-when two or more elements mix, a chemical reaction takes place
-chemical reactivity depends on the number of valence electrons
-in order for an element to be considered stable/unreactive, it must have a full outer shell
-to get a full outer shell an atom can:
gain, lose, or share electrons
chemical reactivity-hydrogen
- has 1 valence electron
- can gain an electron to fill its outer shell
- it can also lose an electron to “fill” its outer shell
- is very, very reactive and explosive
chemical reactivity-alkali metals
- has 1 valence electron
- will lose the 1 electron, rather than gain 7 more to fill the outer shell
- are very reactive
chemical reactivity-alkaline earth metals
- have 2 valence electrons
- would rather lose 2 than gain 6 more
- less reactive than alkali metals
- still very reactive because its quite easy to lose 2 electrons, but not as easy as losing one
chemical reactivity-chalcogens
- have 6 valence electrons
- would rather gain 2 electrons that lose all 6
- are quite reactive, since it is fairly easy to find 2 electrons, not as reactive as haolgens
chemical reactivity-halogens
- have 7 valence electrons
- will gain 1 more electron to fill their outer shell(easier than losing 7)
- very reactive because, like alkali metals, they are very close to being like the noble gases so they react vigorously to gain an electron
chemical reactivity-noble gases
- have 8 valence electrons which means there outer shell is full
- this means they are unreactive
- does not want to mix or react with other elements
who is John Dalton
atomic model= the billiard ball
- said that atoms were tiny particles that could not be divided.
- atoms of the same elements are exactly alike
- atoms are nether destroyed or created
who is J.J Thompson
atomic model= the plum pudding model
- discovered electrons in 1897.
- studying the effects of electricity passing through a gas
- It proved that smaller particles inside the atom existed
who is Ernest Rutherford
atomic model=the planetary model
- the nucleus is a very tiny and positively charged core of an atom.
- looked like the sun (nucleus) and the planets orbiting around it (electrons)
who is Niels Bohr
atomic model=electron shell
- electrons orbit around the nucleus in paths (orbits or shells that are circular)
- each orbit was a certain distance from the nucleus and could only hold a certain number of electrons
what is qualitative data
-physical property of a characteristic of a substance that can be described but not measured
what is quantitative data
- Quantitative physical property is a characteristic of a substance that can be measured numerically
- density is very useful in quantitative physical properties
density
- how tightly packed atoms are in a space or substance
the formula for finding density- mass-volume=density
or the pyramid=mass on top and density on the bottom left with volume on the right (cover which ever you are trying to divide
solutions
- in a solution, the different substances that make it up are not separately visible
- one substance is dissolved in another
- sometimes called homogenous mixtures
mechanical mixture
-different substances that make up the mixture are visible
-sometimes its easy to see the different parts of the mixture and other times it is not
sometimes called heterogeneous mixtures