Elements, compounds and mixtures Flashcards
who introduced the word ‘element’ into the language of chemistry?
IN 1661 Robert Boyle, an Irish scientist, introduced the word ‘element’ into the language of chemistry
Definition of an element
An element is a substance that cannot be split up into simpler substances by chemical means. Elements contain only one type of atom.
How many elements have we discovered?
over 100 elements (118 elements)
Where are all of the known elements listed?
They are listed in a table called the periodic table of the elements.
What does each element have?
Each element has its own symbol, which is a shorthand way of representing the element. It also is used to represent one atom of the element.
What can the symbols for elements be? give examples of each.
They can be the first letter of their name which is always in capital e.g H is hydrogen, or it could be the first letter and another in its name e.g Chlorine is Cl, sometimes the symbols for elements are taken from the Latin names for the elements. e.g Silver (Argentum) is Ag.
Definition of a compound
A compound is a substance made up of two or more different elements combined together chemically. Compounds contain two or more different types of atoms.
Name a compound, mention the elements needed to make it and its chemical formula.
Water is a compound that is made up of two elements, hydrogen, and oxygen. Since there are two atoms of hydrogen for every one atom of oxygen, we say that the chemical formula is H2O which is just a shorthand method used to represent water.
How many compounds are there approximately?
There are millions of compounds.
How are compounds formed?
Compounds are formed when elements combine together in a chemical reaction.
The properties of a _______ usually differ completely from those of the _______. Give an example of this.
The properties of a compound usually differ completely from those of the elements e.g. magnesium is a shiny metal and oxygen is a colourless gas. When these elements combine chemically, they form a white solid.
What is the definition of a mixture?
A mixture of two or more different substances mingled with each other but not chemically combined.
Examples of mixtures in everyday life.
Air, crude oil, toothpaste, cement
Name two important things about mixtures.
The substances in the mixture ate just mingled together, they are not chemically combined.
In a mixture, the substances that make up the mixture can be present in any amounts.
Give an example of a mixture turning into a compound and explain the conclusion of the experiment and the chemical formula.
To make a mixture using iron and sulfur and then change the mixture into the compound iron sulfide.
When iron filings and sulfur are mixed together, no new substance is formed and can easily be separated
with a magnet.
When they are mixed together and heated, the mixture glows, which indicates that a chemical reaction is taking place and that heat is being given off (exothermic reaction.
Iron sulfide is formed and is a compound.
Fe + S = FeS
Iron + Sulfur = iron sulfide
This cannot be separated easily with a magnet now.
