Topic 2 – Changes in Matter YAY! Chemistry!  Topic 2 – Changes in Matter

Properties Every kind of matter has certain properties that can help to classify it. Properties are the characteristic ways in which a substance behaves.

Properties Physical Property Any property that can be observed or measured without forming a new substance Examples: Density Color Texture Smell

Examples: Let’s look at two things and describe some of the physical properties of them. 1. Sugar 2. Icing Sugar

What do you know?! QUALITATIVE QUANTITATIVE

Qualitative and Quantitative There are two types of physical properties QUALITATIVE QUANTITATIVE Colour Melting temperature Texture Boiling temperature Taste Density Smell Viscosity Crystal Shape Solubility Malleability Electrical Conductivity Heat Conductivity

Chemical Properties The way substances react with other substances. Examples: Reacts with water – Sodium (Alkali Metals) Reacts with air – Pure iron (rust) Reacts with pure oxygen Reacts with acids Toxicity Stability (radioactive) - Uranium Combustibility

Example – Table Salt (Sodium Chloride – NaCl) Physical Properties: Appearance: colourless crystals or white powder Melting point: 804 C Boiling point: 1413 C Chemical Properties: Toxicology: May cause eye irritation Reacts with water: No Reacts with Air: No

Example of Properties You have two balloons. One is filled with hydrogen and one is filled with helium. How will you tell which is which? Properties Helium Hydrogen Color Colourless Density Low (0.18 g/L) Very Low (0.09 g/L) Combustibility Does not burn Burns explosively

Properties can CHANGE! How can properties change? Lets look at a piece of paper. What does it look like? What does it feel like? What is it used for?

Two kinds of changes Physical Change A substance changes in form but not in chemical composition NO NEW SUBSTANCES ARE FORMED EXAMPLE: Ice melting. This is a state change that can be easily reversed Paper crumpling Salt dissolved in water

Properties of Matter Physical Changes

Chemical Change Causes one or more new substances to be formed. A chemical change may be difficult or impossible to reverse Examples: Burning paper – the smoke that escaped and the black solid that is left behind (carbon) cannot be recombined to form paper again

How do you tell if it is physical or chemical? IT CAN BE VERY DIFFICULT TO TELL IF SOMETHING IS A PHYSICAL OR CHEMICAL CHANGE

If you make TWO OR MORE of the following observations, then a CHEMICAL CHANGE has probably taken place 1. Heat is produced or absorbed 2. The starting material is used up 3. There is a change in color 4. A material with new properties forms 5. Gas bubbles form in a liquid 6. A precipitate forms in a liquid 7. The change is difficult to reverse.

Changes in Matter Physical Changes Chemical Changes A substance changes form but not chemical composition Chemical Changes Causes one or more new substances to be formed. It may be impossible to reverse.