C1 Flashcards
What are all substances made up of?
Atoms
How many types of atoms are there?
About 100
What is the smallest part of an element?
The atom
What is an element ?
A substance made up of only one type of atom . Can have many different properties( gas ,solid , shiny , metal)
Why are there chemical symbols?
Need to be understood in all languages
What are the columns called and what do they contain?
Groups , each group contains elements with similar chemical properties
What divides the metals and non metals?
The stair case
What state are the vast majority of substances?
Compound
What is a compound?
Different types of atoms bonded together
What is a molecule?
A group of two or more atoms bonded together
How is a compound formed ?
A chemical reaction
What bonds do compounds have ?
Chemical bonds , holding it tightly together.
How are atoms of each element represented in the periodic table?
With a chemical symbol , eg. O for oxygen
What does the periodic table show?
All the elements
What does a chemical reaction always involve?
The formation of one or more new substances , and often a detectable energy change.
How can a compound be separated?
Through a chemical reaction
How can compounds be represented ?
Use the symbols of the atoms
Hydrogen + oxygen —> water , what are the reactant[s]and what are the product[s]
Hydrogen + oxygen , reactants
Water , product
What do symbol equations help you see?
The amount of a substance involved
What is the law of conservation of mass?
Atoms cannot be created or destroyed
What does it mean for an equation to be balanced?
The total mass of the products is equal to the total mass of the reactants. Energy cannot be created or destroyed so equations must be balanced
What are the state symbols?
S=solid
G=gas
L=liquid
AQ=aqueous
Balance this equation?
H2 + O2 —-> H2O
- List out the mass on both sides and add until you get the same on both sides
Answer: 2H2+O2 —> 2H20
What is a mixture ?
Made up of 2 or more elements or compounds not chemically bonded together . The chemical properties of each substance remains unchanged.
Features of a compound?
- Fixed composition
- chemical reactions must take place to separate elements in a compound
- chemically bonded
Features of a mixture?
- No fixed composition
- can be separated more easily
- no chemical bonds
What are the separation techniques?
- filtration
- crystallisation
- distillation
- chromatography
What is filtration ?
Used to separate substances that are insoluble in a particular solvent from those that are eg. Sand and salt in water
What does soluble mean ?
Able to be dissolved in water.
What is a solvent?
The liquid in which a solute is dissolved to form a solution.
What is distillation?
Distillation collects the solvent when a solid and solvent are separated , rather than evaporating it.
What does chromatography do?..
Mixtures of substances can be separated using it.
Steps in chromatography?
- Draw a horizontal line near the bottom of the paper
- Place a dot of each colour on the line using a capillary tube
- Place the paper in a beaker so that the bottom of the paper is just in the water
- Use the ruler to measure the distance travelled by each dot from the starting line and the distance the water has travelled to find the retention factor
How to calculate the retention factor?
Distance moved by substance/ distance moved by solvent
Steps for distillation?
Ink consist of a coloured substance dissolved in water.when the ink is boiled the water turns to steam and condenses in the test tube. The colourless substances remain in the flask
What is crystallisation ?
- obtain a pute sample of salt from a salt solution .
- separate Nacl from the water
- can evaporate the water
Two ways to separate soluble liquids?
- evaporation
- crystallisation
Steps for crystallisation?
- Pour the solution into an evaportaing dish and gently heat the solution
- Once some of the solvent has evaporated , or when you see crystals starting to form , remove the dish from the heat and leave the solution to cool
- The salt should start to form crystals as it becomes insoluble in the cold , highly concentrated solution
- filter the crystals out of the solution and leave them on a warm place to dry
What is fractional distillation ?
-separation of a liquid mixture into fractions differing in boiling point by separation of distillation typically using a fractionating column .
Who was john dalton?
Said substances were made up of atoms
Who discovered the plum pudding model ?
JJ thompson
Who discovered the electron?
JJ thompson
What did the plum pudding model suggest?
The atom is a ball of positive with negative electrons embedded in it .
How was the nucleus discovered?
Alpha particle scattering experiment led to the conclusion that the mass of the atom was concentrated at the centre (nucleus) and the nucleus was charged , the nuclear model replaced the plum pudding.
How did Nicolas Bohr adapt the nucleus model?
Suggested electrons orbit the nucleus at specific distances. The theoretical calculations of Bohr agreed with the experimental observations.
What did james Chadwick discover ?
Provided evidence to show existence of neutrons within the nucleus.
What are the differences between the plum pudding model and the nuclear model ?
Plum pudding
-positively charged with electrons spread out inside .
Nuclear model
- nucleus positively charged
- most mass inside the nucleus
- mostly empty space
- electrons orbit around the nucleus
What are the subatomic particles in the atom?
- protons
- neutrons
- electrons
Where is the mass of an atom concentrated?
The nucleus
What is the relative charge of a proton?
+1
What is the relative charge of a neutron?
0
What is the relative charge of an electron?
-1
What is the relative mass of protons?
1
What is the relative mass of neutrons?
1
What is the relative mass of electrons?
0 , Nothing pretty much . 1/2000 of a proton
What is the charge of an atom?
0 as protons and electrons cancel each other out
What do all atoms from a particular element have in common?
All have the same number of protons
What is the atomic number?
The number of protons in each atom of an element
What are elements ordered in ?
There atomic numbers
What does the atomic number tell us , other than the number of protons?
The number of electrons
What is the mass number ?
The mass of the atom
How to find the mass number ?
Protons + neutrons = mass number
What is an ion?
A charged atom
How is an ion formed ?
If an atom loses or gains electron[s]
What happens if an atom gains an electron?
It has a negative charge . It has become a negative ion
What happens if an atom loses electrons?
Becomes a positive ion
What charge would a oxygen ion have?
0^2-
8 electrons , 6 on the valence shell , so you add two electrons which makes a negative of 2 charge
How big is the atom ?
7 x 10^27
What is the radius of the atom?
0.1 nm
How big is the radius of the nucleus?
1/10000 of the atom
Where is almost all of the mass concentrated?
In the nucleus
Which is the mass number and atomic number ?
23
Na
11
Top is mass
Bottom is atomic
What is an isotope ?
Atom of the same element with different number of neutrons
What does an atom becoming an isotope change?
The mass of the atom.
What can extra neutrons in the nucleus do to the stability of the atom?
Make it unstable , radioactive. Not all isotopes are radioactive though.
What happens to the physical properties of different isotopes?
May differ eg. Density , radioactivity
What happens to the chemical properties of different isotopes?
Stay the same as their reactions depend on the electronic structure . Same protons and electrons
What is the outer shell of an atom called?
The valence shell
How many electrons can the first shell hold?
2
How many electrons can every shell hold except for the first one ?
8
What is the most and least reactive shell?
Most: valence
Least: the first shell
What is the electronic structure of sodium?
Atomic number of 11
2,8,1
What do all atoms in the same group have in common in terms of their electronic structure?
All atoms in the same group have the same number of electrons on their valence shells. Eg. All group 1 elements have 1 electron on the outershell.
What do the chemical properties of an atom depend on?
How many electrons it has eg. Group 1 metals all react similarly in chemical reactions
What is a noble gas?
Group 0 , very stable , 8 electrons on the valence shell.
What is crystallisation?
Separates solutions into their constituent (different) parts: dissolved solids (solutes) and liquids (solvents).
