Characteristics of Substances Elements, compounds, mixtures

Atoms Smallest piece

Elements Red block Blue block Each type of Atom is called an Element LEGO WORLD Different colours ,sizes and shapes Different properties

Elements are substances made up of only one type of atom. Example:

Molecules A molecule is made up of two or more atoms chemically combined. Water (H2O)

Chemical Reaction Element or Molecules combining together = > Chemical Reaction O H Water (H2O) O H +

Aristotle's Elements Earth Air Fire Water

What is an Element ? Everything in the Universe is made from Elements There are over 100 elements The most common element in the Universe is Hydrogen The Term “Element” was introduced by an Irish scientist Robert Boyle – “Simple Substance”

Element An Element is a substance that cannot be split up into simpler substances by chemical means.

Common Elements

Oxygen – Most abundant Element in Earths Crust

What is this ? Element Percentage Oxygen 65% Carbon 18% Hydrogen 10% Nitrogen 3% Calcium 1.5% Phosphorus 1.0% Potassium 0.35% Sulfur 0.25% Sodium 0.15% Magnesium 0.05% Copper, Zinc, Selenium, Molybdenum, Fluorine, Chlorine, Iodine, Manganese, Cobalt, Iron 0.70% Lithium, Strontium, Aluminium, Silicon, Lead, Vanadium, Arsenic, Bromine Trace amounts Reference: H. A. Harper, V. W. Rodwell, P. A. Mayes, Review of Physiological Chemistry, 16th ed., Lange Medical Publications, Los Altos, California 1977. Most of the human body is made up of water, H2O, with cells consisting of 65-90% water by weight. Therefore, it isn't surprising that most of a human body's mass is oxygen. Carbon, the basic unit for organic molecules, comes in second. 99% of the mass of the human body is made up of just six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus.

Periodic Table of Elements

Symbols Each Element is given a unique Symbol First letter of its name (H, C, O) First two letters of its name (Si, Ne, Li) Taken from its Latin name (Pb, Fe, Au)

Metals METAL SYMBOL Copper Cu Zinc Zn Aluminium Al Iron Fe Silver Ag Gold Au

Non Metals NON METAL SYMBOL Carbon C Oxygen O Sulphur S Hydrogen H Nitrogen N

Atom An Atom is the smallest particle of an Element that still retains the properties of that element.

What’s inside the atom?

Compounds A Compound is a substance that is made up of two ore more different elements combined chemically together.

Compounds H C O H H Water (H2O) Methane (CH4) C O Carbon Dioxide (CO2)

Compound ? O O Oxygen (O2) H H Hydrogen (H2)

When a compound is formed during a chemical reaction its properties differ from those of the elements from which it is made

Mixtures A mixture consists of two or more different substances mingled together but not chemically combined. Examples: Sea – water and salt Air – nitrogen, oxygen … Soil – sand, clay, humus …

Mixture vs Compound MIXTURE COMPOUND

Mixture Compound The amounts of the substances in the mixture can vary. The elements in a compound are always present in the same fixed proportion. A mixture contains two or more substances A compound is a single substance. The properties of a mixture are similar to those of the substances in a mixture. The properties of a compound are different to those of the elements which reacted to form it. There are practically no energy changes when a mixture is made Heat is usually given out or taken in when a compound is formed. It is usually easy to separate the components of a mixture. It is usually difficult to separate the components of a compound.