Topic 3: What are Elements Flashcards
Alchemists
- People who tried to turn lower metals (copper, lead) into precious metals (gold, silver)
What did ancient greek philosophers think everything was made up of?
- Air, water, fire and earth
- They referred to these things as elements
- They believed that everything was made up of a combination of these elements
Antonie Lavoisier
- Defined elements as pure substances that could not be broken down into simpler substances
- Identified 23 pure substances as elements
- Developed techniques such as measuring the substances involved in the chemical change
- Created the Law of Conservation of Mass
Property
- A characteristic of a substance that helps it describe it
Physical Change
- A change in form but not in chemical composition
- No new substances are formed
Ex. ice melting
Chemical Change
- A change to a substances composition
- A new substance is formed
Ex. dying hair, burning toast,
What clues show that a chemical change MAY have taken place?
- Energy is absorbed or emitted
- Theres a change in color or oder
- Bubbles or solid form appear in liquid
- The change is difficult to reverse
What clue shows that a chemical change has DEFINITELY taken place?
- A new substance is formed
Physical Properties of Matter
- Melting Point
- Boiling Point
- Hardness
- Malleability
- Ductility
- Crystal Shape
- Solubility
- Density
- Conductivity
Melting Point
- Temperature at which the substance changes from a solid to a liquid
Boiling Point
- Temperature at which substances changes from liquid phase to gas phase
Hardness
- Substances ability to resist being scratched
- Moh’s hardness scale
Malleability
- Ability to be pounded or rolled onto sheets
Ductility
- Substances ability to be stretched into a long wire
Crystal Shape
- Shape of a substances crystals
Solubility
- Ability of a substance to be dissolved in another substance
Density
- the amount of mass in a given volume in a substance
Conductivity
- Ability of a substance to conduct electricity or heat
Law of Conservation of Mass
- In chemical change, the total mass of the new substances is always the same as the total mass of the original substances
Law of Definite Composition
- Compounds are pure substances that contain two or more elements combined together in fixed proportions
Electrolysis
- The process of using electricity to split water to get hydrogen and helium
John Daltons Atomic Theory
1.All matter is made up of small particles called atoms
2. Atoms cannot be created, destroyed or divided into smaller particles
* Atoms can be divided into smaller particles
3. Atoms of the same elements are the same mass and size. Different elements will have different sized atoms
4. Compounds are created when atoms of different atoms link together in definite proportions
Qualitative
- Information or characteristic of a substance that can help describe it
- Quality
Quantitative
- Characteristic that can be measured numerically
- Quantity
JJ Thomson
- Discovered sub atomic particles
(particles smaller than atoms) - Discovered electrons using light rays
Ernest Ruthford
- Discovered atomic nucleuses by shooting positively charged particles through thin gold foil
- Discovered protons
Neils Bohr
- Suggested that electrons move in specific circular orbits, or electron shells
Atomic Nucleus
- Mass at the center of the atom
Proton
- Have a positive charge
- Found inside the atomic nucleus
- Has a very large mass
- Symbol is P
Neutrons
- Found inside the nucleus
- Have the same mass as protons
- Have no net charge
- Symbol is N(0)
Electrons
- Have a negative charge
- Found outside the nucleus
- Have very little mass
- Symbol is e
