Flashcards in EXAM Science Deck (72):
What is an Atom
Atoms are the smallest particle of a substance that can still exist and still be that substance
What's in the Nucleus
Protons and Netrons
What are shells and what are they also known as?
Are electrons grouped around the nucleus in regions, they are also known as energy levels
Neutral atoms are...
Atoms that have the same amounts of protons as electrons. All atoms are neutral
It is equal to the number of protons
Is equal to the number of protons added to the number of neutrons
How many elements in periodic table
What are the 2 settings of the periodic table
Groups - Columns
Periods - Rows
How many elements found on earth
What are groups and what are the names of group 1,2,17 and 18
Groups are vertical columns that show how many electrons in the outer shell and so they all have similar chemical properties.
Group 1 are alkali metals
Group 2 are alkaline earth metals
Group 17 are halogens
Group 18 are noble gases
A substance that contains only 1 type of atom
Atoms are tightly blinded together with more substances
How are compounds separated
Electricity, fire, mixing it with other compounds
2 or more elements together but not combined
How are mixtures separated
Standing and decanting, heating and evaporating and filtration and magnets
A change of a substance but no bonds are broken - can tell if it goes back to it's original state
A change that breaks the bonds between other elements - can tell if new element is formed and difficult to reverse
How can you tell chemical change
Cloudiness appears in liquid or gas, odour, bubbles, increase or decrease temperature, light or flame, change in colour but certain is to detect new element
It is an example of corrosion a flaking substance that forms
What are isotopes?
They are atoms with the same number of protons, but a different number of neutrons. They have the same atomic number but different mass numbers
Show the isotopic representation
Mass Number-> a
X <---- symbol
Atomic Number-> z
What are valence shells?
They are the outer shells, they can never have more than 8 electrons and are the easiest electrons to remove from the atom
How do you draw and write the electrons of an atom?
You draw them in pairs around the nucleus which shows either the elements symbol or the number of protons. You write them order from inner shell to outer, e.g. Carbon 2,4
How are elements ordered in the periodic table?
In increasing atomic number
What are periods?
They at horizontal rows that have the same number of shells. They are numbered 1-7
Know where the metals, non-metals, metalloids and transition metals are.
What is ionic bonding?
When an atoms loses or gains electrons in order to become more stable. Metals give away electrons and non-metals gain electrons.
What are cations and anions
When metals gives away electrons it becomes a cation as it is positive
When non-metals receive electrons it becomes an anion as it is negative
Know how to draw an electron transfer diagram
What are covalent bonds?
This is when non metals chemically combine to share electrons with others. These shared electrons hold them together
Know how to draw electron dot diagrams (Lewis) and the three stages - Lewis, valence structures and structural formula
What are the 3 common acids and their formulas
Hydrochloric acid - HCl
Sulfuric acid - H2SO4
Nitric acid - HNO3
Endothermic reactions absorb so that the reaction may occur. The products have a greater energy level than the reactants
Exothermic reactions release energy in order for it to occur. It is seen that the reactants have a greater energy level than the products.
What are the 7 types of reactions?
Precipitation reactions, decomposition reactions, combination reactions, corrosion reactions, combustion reactions, metal displacement reactions and neutralisation reactions
What is a precipitation reaction?
Who's two solutions are mixed together and they form a precipitate. You would then have 2 aqueous reactants and one solid and one aqueous products.
What are decomposition reactions?
During a decomposition reaction one single chemical substance is seen to be broken down into 2 or simpler chemical compounds or elements. There is one reactant and several products.
What is a combination reaction?
This is the opposite to decomposition reactions as they have several reactants and only one product formed.
What is a corrosion reaction?
This is where the metal is eaten away by substances in the air (dry corrosion) or in the water (wet corrosion).
Iron + oxygen -> iron(III)oxide (rust)
What is a combustion reaction?
This is when a chemical substance burns in the presence of oxygen. These are Exothermic reactions. The reactants must include oxygen and the reactants are always carbon dioxide and water.
How do you balance a combustion reaction?
First you balance the carbon atoms, then the hydrogen atoms and finally the oxygen atoms.
What is a metal displacement reaction?
Thai involves removing one element and replacing it with another. This is seems when zinc and copper(II)nitrate come in contact. The nitrate and copper swap positions through displacement and copper and zinc nitrate are the products.
What are neutralisation reactions?
When acid reacts with a metal hydroxide and the products are a salt and water.
When acid reacts with a metal carbonate and the products are a salt, carbon dioxide and water
When acid reacts with a metal oxide and the products are a salt and water.
What is metallic bonding?
Metallic bonding has many properties. The are good conductors of electricity and heat, they are lustrous (shiny), the are malleable and ductile, they have high melting and boiling temperatures and metals are generally dense.
What is evolution?
Evolution is the change in organisms over time
What is a species?
Similar individuals that can breed to produce fertile offsprings
What are the levels of classification?
What is adaption?
It's a special feature or characteristic that improves an organism’s chance of survival in its environment
What are examples of structural adaption
Streamline body shape in marine enviroments
What is an example of behavioural adaption
What is a physiological (functional) adaption
Concentrated urine in desert cats
Who was Charles Darwin
He was a British scientist who came up with the theory of evolution
What are the Galapagos Finches
These are the birds Charles Darwin noticed that on each island a different type of Finch was found. The differences suited the environments in which they lived. Some had beaks that helped them crack seeds that were in an abundance on their island whilst others has beaks more suited to eating softer foods found on their own island.
Define Natural selection
Creatures best suited to their environment are more likely to survive and reproduce, passing on the characteristics that helped them to survive.
What are the 4 stages in the process of natural selection
1. Variation can been seen in a species
2. Some characteristics are better suited to the environment that others
3. There is a "struggle for survival." Those who inherit the most fit characteristics are more likely to survive
4. These characteristics are passed on to their offspring and will increase in numbers
What are the 5 types of evidence for evolution?
Fossil records, Comparative anatomy, Comparative embryology, Chemical similarities and Geographic distribution
What are fossil records
Fossils are the preserved remains, impressions or traces of organisms found in rocks of different ages. There is direct evidence (bones and hair) or indirect evidence (moulds and footprints)
What is comparative anatomy
Similarity in structure are called 'homologous structures.' They show an evolutionary relationship between these organisms. That is they are related in some way
What are Analogous structures?
They are similar structures, but they have evolved independently of each other. That is, they are not related. This is like a dolphin (a mammal) and a shark (a fish)
What is Comparative Embryology
In the early stages of development the embryos of different organisms are very similar. Humans had gills and tails in the womb
What are Chemical Similarities
Similarities in DNA of related species and similarities in proteins
What is Geographical Distribution?
Biogeography is the study of the geographical distribution of fossils and living species
What is the Law of Conservation of mass
The mass of the reactants will always be equal to the mass of the products
What does it mean by survival of the fittest?
It means that those with the most desirable traits will survive and pass traits on
What is speciation?
Over many generations, an isolated population may be subject to selective pressures.this can cause an isolated species to change over time. When the isolated species is reunited, the cannot reproduce as a new species has formed
Define common ancestor
A common ancestor is an extinct species of which had many offsprings. Whether it was because of speciation or adaption these offsprings changed into different species. This therefore means that although we are related to apes, we have a common ancestor and are on different branches of the tree.
What are Homologous structures?
They show an evolutionary relationship between organisms meaning they are related in some way
What is extinctuon?
The loss or disappearance of a species. Humans hunted Dodo birds to extinction for food. The North American Bison is extinct because white man hunted them for food and the cattle ate their food and gave them diseases.
What is convergent evolution?
Similar selection pressures or environments result in unrelated organisms having similar features.
What is divergent evolution?
New species evolve from a common ancestor
What is biodiversity and what are threats to it by humans
The variety of all life forms on earth. That is, the different plants, animals and ecosystems they are part of. By creating cities and pollution we are destroying many environments