Lecture 1 Scientific Method Ozgur Unal NIS - chemIstry Lecture 1 Scientific Method Ozgur Unal

Scientific Method Science is a process that uses observation and investigation to gain knowledge about the events in nature. Observation: Act of gathering information Investigation: Includes observing, experimenting, modelling Scientific method is a systematic approach used in scientific study.

Scientific Method Hypothesis: An educated guess Experiment: A way to test hypothesis Collect data Analyze data Draw conclusions Experiments include variables: Dependent variables Independent variables Constants

Scientific Method In experiments, two types of data can be collected: Qualitative data: Anything that relates to five senses Quantitative data: Numerical information Observe the liquid shown to you. Record your qualitative and quantitative data

Scientific Method Question: Does salt dissolve faster in hot water or water at room temperature? Hypothesis? Design an experiment to test your hypothesis. Identify independent & dependent variables and constants

Scientific Method A theory is an explanation of a natural phenomenon based on many observations and investigations over time. (Electromagnetic Theory) A scientific law is a concise but general statement about how nature behaves. (e.g F=m*a)

Lecture 2 The Ozone Layer and Chemistry Ozgur Unal NIS - chemIstry Lecture 2 The Ozone Layer and Chemistry Ozgur Unal

ULTRAVIOLET RADIATION UV light in electromagnetic spectrum is more energetic than visible light. Dangerous for living things. What does protect the living things from UV light coming from the Sun?

OZONE LAYER Ozone layer in the atmosphere protects life from UV light. http://svs.gsfc.nasa.gov/vis/a000000/a000800/a000834/index.html Ozone, which is made up of oxygen, is a substance in the atmosphere that absorbs UV light. A substance, which is also known as a chemical, is matter that has a definite and uniform composition, like pure water. Ozone layer is located in the stratosphere.

OZONE LAYER How does ozone enter atmosphere? UV light 3 O2 -------------------------------------------------------- > 2 O3 Ozone was first identified and measured in the late 1800s. It makes a convenient marker to follow the flow of air in the stratosphere.

OZONE LAYER British scientist G.M.B. Dobson began measuring the amount of ozone in the atmosphere in the late 1920s. Normal levels of the amount: 300 Dobson units (DU) At the beginning of the 1980s, a research group found levels of ozone as low as 160 DU The reports showed a decrease in the thickness of the ozone layer. What could be the reason for the thinning of the layer?

cfc Large scale production of refrigerators and air-conditioning units that use CFCs (chlorofluorocarbon) as coolers were being produced by 1930s. CFCs were also used in spray cans. CFC is a substance that contains Chlorine, Fluorine and Carbon. It does NOT occur naturally. It does not readily react with other substances. This is why scientists thought it was safe for the environment.

cfc Scientists first began to detect the presence of CFCs in the atmosphere in the 1970s. They measured the amount of CFCs and saw a year after year increase in the amounts. By 1990, the CFC concentration has reached an all time high. Increasing level of CFCs and the thinning in the ozone layer. Could they be connected?

Solution for ozone hole Scientists determined that CFCs and also two other substances (carbon tetrachloride and methyl chloroform) react with ozone and harm the ozone layer. Ozone layer is an international concern. In 1987, world leaders met in Montreal and signed the Montreal Protocol. The Protocol phased out the use of these substances and put some restrictions on how they should be used in the future. The CFCs concentration declined after the protocol.