Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
THE SCIENCE OF CHEMISTRY 1.1 What is Chemistry? 1. Are there “good” chemicals and “bad” chemicals? 2. Are there any chemicals that you can never have too much of? What is matter? • Matter is anything that has volume and mass What is a chemical? • Any substance with a definite composition – can be a single atom or a large molecule Physical properties Examples: Mass Density Color Physical properties can be measured or seen through direct observations. PHYSICAL CHANGES Words such as boil, freeze, melt, and condense are used to describe physical changes. So are words such as break, split, grind, cut, and crush. There is a difference between these two sets of words. Each set describes a different type of physical change. PHYSICAL CHANGES Physical changes can be classified as reversible or irreversible. Melting is an example of a reversible physical change. PHYSICAL CHANGES All physical changes that involve a change from one state to another are reversible. Cutting hair, filing nails, and cracking an egg are examples of irreversible physical changes. Chemical properties are observed when a substance changes into a different substance. Iron Chemical change Rust The Law of Conservation of Matter Matter can neither be created nor destroyed….WHAT GOES IN MUST COME OUT!!! a. The Evolution of a Gas The production of a gas is often observed by bubbling, or by a change in odor. b. The Formation of a Precipitate When two clear solutions are mixed and become cloudy, a precipitate has formed, as shown in. c. The Release or Absorption of Energy A change in temperature or the giving off of light energy are signs of an energy transfer. d. A Color Change in the Reaction System Look for a different color Signs that a chemical change has occurred