Atoms, Elements, Compounds & Mixtures Flashcards
What is an atom?
Atoms are tiny, tiny particles.
An atom is the smallest part of an element that can exist.
Define Dalton’s model on atoms
Dalton’s model on atoms
- All matter is made up of atoms
- There are different types of atoms
- Each element contains a different type
What is an element?
Element is a substance that contains only one type of atoms
Give examples for elements
- Oxygen
- Nitrogen
- Gold
- Silver
- Copper
What is a compound?
Compounds form when different atoms join together.
What is a molecule?
Molecules are when two or more atoms are chemically joined together
Molecules can be
- element - same type of atoms joined together - O2
- compound - different types of atoms joined together - CO2
What is the difference between a compound and mixture?
In a compound elements are chemically joined together.
In a mixture elements are not chemically joined together.
What is a mixture?
A mixture contains two or more substances not chemically joined together.
What is a pure substance?
A pure substance is made up of only one type of element or one type of compoud.
It can’t be separated into anything simpler witout a chemical reaction e,g: water H2O
What is the difference between an element, a compound and a mixture?
An element has only one type of atom.
A compound has more than one type of atom, chemically joined.
A mixture has more than one type of atom or compound, not chemically joined.
What is a physical change?
Physical Changes
- Physical changes are changes in appearance
- A new substance is not created e.g. broken glass
- Chemical bonds are not broken or formed
How many elements there?
There are 92 elements.
Is water a compound? Explain your answer.
Water is a compound.
Two elements- hydrogen and oxygen are chemically joined together in water.
Define catalyst
Chemists use catalysts to speed up slow reactions if they want to make a product more quickly.
A catalyst is not used up in a reaction.
Salt is an element or compound?
Salt is a compound - NaCl
Salt contains two elements - sodium and chlorine.
Salt chemical name is sodium chloride.
Describe the properties of sodium, chlorine and sodium chloride.
Sodium is a shiny metal. It fizzes in water.
Chlorine is smelly green poisonous gas.
Sodium chloride is salt and used in food all the time.
State the number and type of atoms that make up one carbon dioxide molecule.
Carbon - 1 atom
Oxygen - 2 atoms
Carbon dioxide and carbon monoxide are gases.
Which gas is poisonous?
Carbon monoxide
Define chemical formula
A chemical formula shows the ratio of atoms of each element in the compound
What is a chemical reaction?
A chemical reaction is a change in which atoms are rearranged to create a new substance.
Give examples of two types of physical change
Physical changes
- Dissolving
- Changes of state
State three examples of useful products made in chemical reactions
- Medicines such as paracetamol
- Fabric such as polyester
- Building materials such as cement
Chemical reactions also transfer …………
Why is this useful?
Chemical reactions also transfer energy.
- Burning petrol makes vehicles go
- Burning coal heats water to produce steam to generate electricity
Name two chemical reactions which are not useful
- Iron rusting is a chemical reaction.
It damages cars, boats and bridges.
- Chemical reactions make food rot.
