Presentation on theme: "By Liz LaRosa 5 th Grade Science www.middleschoolscience.comwww.middleschoolscience.com 2009 Classifying Matter: Elements, Compounds, and Mixtures."— Presentation transcript:
By Liz LaRosa 5 th Grade Science www.middleschoolscience.comwww.middleschoolscience.com 2009 Classifying Matter: Elements, Compounds, and Mixtures
Pure Substances A sample of matter that has definite chemical and physical properties.
Elements pure substance that cannot be separated into simpler substance by physical or chemical means.
Note that an element: Consists of only one kind of atom, Cannot be broken down into a simpler type of matter by either physical or chemical means Can exist as either atoms (e.g. argon) or molecules (e.g., nitrogen). Elements
Examples of elements Elements are made up of tiny particles Elements can be further classified into two groups: Is the smallest particle of an element and has the same chemical properties of the element Is made up of two or more atoms that are chemically bonded together (note: these atoms are of the SAME element!!) Hi, I am from the “Noble gas” family and I work alone We same same!!
These are elements! Atoms of same element Cu copper element Na sodium element He helium element Molecules of same element H Hydrogen gas element O H OO ozone
Atoms An element is made of tiny particles called atoms. The atoms of an element is different from that of another element.
Molecules Very few elements exists as atoms besides elements such as helium and neon. Most elements exist as molecules. For example, hydrogen is H 2. Ozone is O 3.
Chemical Symbols of Elements Chemists use symbols to represent elements. For example, O represents oxygen while Fe represents iron. ElementSymbolElementSymbol CalciumCaMercuryHg CarbonCNeonNe HydrogenHSiliconSi IronFeSodiumNa
Classification of Elements – Metals and Non-metals There are two major groups of elements – metals and non-metals. Iron is a metal. Oxygen is a non-metal. There are some elements called metalloids which behave like both metals and non-metals. Metals and non-metals are grouped separately on the Periodic Table.
What is an element? An element is a substance that cannot be broken down into two or more simpler substances by any chemical means. - They are arranged in the Periodic Table, classified as metals and non-metals. - They may consist of atoms of same element or molecules of the same element. Metals (excluding hydrogen) Non-metals (including hydrogen)
Compounds Pure substance composed of two or more different elements joined by chemical bonds. Made of elements in a specific ratio that is always the same Has a chemical formula Can only be separated by chemical means, not physically
Compounds Note that a compound: can be broken down into a simpler type of matter (elements) by chemical means (but not by physical means), has properties that are different from its component elements, and always contains the same ratio of its component atoms.
Making compounds from their elements Example: Making iron sulphide compound Iron + sulphur iron sulphide elements compound + yellow grey heat black
How to read a formula H20H20H20H20 This is a subscript. It tells us how many atoms of that element exist in one unit of that compound. Hydrogen is made of 2 H atoms and 1 O atom. No subscript is used when only one atom of an element is present.
Mixtures A combination of two or more pure substances that are not chemically combined. substances held together by physical forces, not chemical No chemical change takes place Each item retains its properties in the mixture They can be separated physically Chem4kids.com
Mixtures Definition of a mixture: A mixture is not a pure substance as it contains a mixture of atoms of molecules which are not chemically combined together.
Mixtures Note that a mixture: consists of two or more different elements and/or compounds NOT chemically combined. Can be homogeneous or non-homogeneous can be separated into its components by physical means, and often retains many of the properties of its components.
Mixtures Examples of mixtures include muddy water and air. Air is made up of gases such as nitrogen and oxygen mixed together.
A mixture of 2 elements A mixture of two elements, e.g. neon (Ne) and hydrogen (H 2 )
A mixture of 1 element and 1 compound A mixture of one element and one compound, e.g. hydrogen (H 2 ) and ammonia (NH 3 )
A mixture of 2 compounds A mixture of two compounds, e.g. water vapour (H 2 O) and carbon dioxide (CO 2 )
Mixture Types MIXTURES MAY BE HOMOGENEOUS OR HETEROGENEOUS
Homogeneous Mixtures Homogeneous Mixtures: The prefix: "homo"- indicates the same Have the same uniform appearance and composition throughout
What is a solution? A solution is a mixture of two or more substances. At least two substances must be mixed in order to have a solution
A solution has two parts The substance in the smallest amount and the one that DISSOLVES is called the SOLUTE The substance in the larger amount is called the SOLVENT - it does the dissolving IN most common instances water is the solvent
Examples of solutions Salt water Clean Air Vinegar
Heterogeneous Mixtures: The prefix: "hetero"- indicates difference A heterogeneous mixture consists of visibly different substances or phases Two or more parts can be seen
Suspensions A SUSPENSION is a heterogeneous mixture of large particles These particles are visible and will settle out on standing Examples of suspensions are: fine sand or silt in water or Italian salad dressing
Can you differentiate? Compound Mixture of element & compound Mixture of 2 elements-Alloy Molecules of an element Mixture of 2 elements
Conclusion An element is a pure substance which cannot be split up into two or more simpler substances by chemical means. A compound consist of a fixed number of different kinds of atoms chemically combined together. A mixture is not a pure substance as it contains a mixture of atoms of molecules which are not chemically combined together.
Mixtures vs. Compounds http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/elements_com_mix_6.shtml
Can you identify the following? You will be shown a series of photos. Tell if each photo represents an item composed of an element, compound, or mixture. Review: An element contains just one type of atom. A compound contains two or more different atoms joined together. A mixture contains two or more different substances that are only physically joined together, not chemically. A mixture can contain both elements and compounds.