Introduction to Chemistry

1. Introduction to Chemistry

2. Matter! • Matter, the stuff of the universe has many different forms • Solids, liquids, gases • Living and non living • Big and small • Naturally occurring in the environment and human made

3. Chemistry • Chemistry is the study of matter and the changes that it undergoes • A basic understanding of chemistry is important to understanding all the sciences: biology, physics, earth science, ecology…

4. Matter and its Characteristics • Matter is anything that has a mass and takes up space • Mass is a measurement that reflects the amount of matter in a substance

5. Matter and its Characteristics • It is easy to see that a book is matter, it is has a mass and obviously takes up space. • Is air matter? You can’t see it and sometimes can’t feel it… if you inflate a balloon, it expands to make room for the air and you can find the mass of the balloon before and after blowing it up to see the change in mass.

6. Matter and its Characteristics • Is everything made of matter? No. • Thoughts in your mind are not matter • Neither is heat, light, radio waves or magnetic fields • Remember that matter has to have a mass and take up space.

7. Mass and Weight • When a person goes to the store to buy vegetables, sometimes they weigh them first on the scale to find the weight. • Weight is a measure of not only the amount of matter in an object, but also the affect of Earth’s gravitational pull on the object • The weight of a human on the moon is different than the weight of a human on earth, but their mass stays constant.

8. What you see and what you don’t… • When you look at a skyscraper downtown what do you see? • Windows • Walls • Doors • Are there things inside the building that you don’t see from the outside?

9. What you see and what you don’t… • Yes! There are beams inside the walls that give the building structure, stability and function. • Much of matter is macroscopic, meaning you don’t need a microscope to see it

10. What you see and what you don’t… • We will learn later on that matter made of elements, and those elements are made of atoms • These atoms cannot be seen with a microscope and are submicroscopic, they are so tiny that 1 million, million atoms could fit into the period at the end of this sentence.

11. What you see and what you don’t… • The structure, composition, and behavior of all matter can be explained on the submicroscopic level • All that we observe about matter depends on atoms and the changes they undergo • Chemistry seeks to explain the submicroscopic events that lead to macroscopic observations

12. Observations • Observations are important in understanding science • Observation is the action of observing (seeing or noticing) something in order to gain information

13. Observation • There are two types of observations: • Quantitative and Qualitative

14. Qualitative Observations • A qualitative observation uses the five senses. • Qualitative observations describe color, odor, shape, texture, taste… • Qualitative observations do not use numbers • Examples: • She has brown hair • The table is smooth • The door is open • The chemical smells sour

15. Quantitative Observations • Quantitative observations use numbers and measurements • Quantitative observations describe how much, how little, how big, how tall, how fast… • Examples: • The rock has a mass of 6g • The worm is 5.4cm long • The bacteria took 21 hours to reproduce • The truck was going 55km/hr

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17. Scientific Method

18. Scientific Method • A scientific method is a systematic approach used in scientific study, whether it is chemistry, biology, physics or any other science. • It is an organized process used by scientists to do research, and it provides a method for scientists to verify the work of others

19. Scientific Method • The steps of scientific method are: • Make Observations • Create a hypothesis • Design an experiment and collect data • Analyze and conclude

20. Observation • An observation is the act of gathering information, either qualitative or quantitative. • As scientists see or notice the world around them they ask questions about their observations and try to find answers

21. What do you see?

22. Game 2: Fossil Footprints Mystery! What is happening at Position 1?

23. What is happening at Position 2?

24. What is happening at Position 3?

25. Hypothesis • A hypothesis is a tentative explanation for what has been observed or a possible answer to a question that has been proposed. • A hypothesis needs to be something that is able to be tested.

26. Experiment • A hypothesis means nothing unless there is data to support it • An experiment is a set of controlled observations that test a hypothesis • Scientists must carefully plan and set up one or more experiments in order to change and test one variable at a time.

27. Experiment • You observe that salt dissolves in water. You wonder how you can change the rate at which salt is dissolved. You propose the hypothesis that increasing the temperature will increase the rate the salt dissolves. Your team places 50g of salt into two beakers of water. You will collect data on time and temperature of the dissolving salt. One beaker is 20⁰C and the other is 40 ⁰C. The 50g of salt in the 20⁰C beaker dissolved in 3 minutes, the salt in the 40⁰C dissolved in 1 minute. You realize that the warmer water dissolved the salt faster than the colder water.

28. Experiment • Variable: the condition that is being changed in the experiment, in this example: temperature • There are two types of variables: • Dependent variable • Independent variable

29. Experiment • An independent variable is a variable that you plan to change or manipulate in the experiment. In this case, temperature. • A dependent variable changes in response to a change in the independent variable, in this case, dissolve rate

30. Experiment • When you increased the temperature, the independent variable, the dissolve rate changed. • The dissolve rate was dependent on the temperature, therefore is called the dependent variable. • If you hadn’t changed the temperature, the dissolve rate wouldn’t have changed. Therefore dissolve rate is dependent on the temperature • Bottom line: the dependent variable is dependent on, or determined by, the independent variable.

31. Experiment • Data is information collected about the observations made. • In this case data was collected the dissolving rate of salt. The mass of the salt was kept constant for both beakers, the amount of water was kept constant for both beakers and the only variable was temperature. • Data was collected on the temperature of each beaker, and the time it took to dissolve the salt. • Often graphs and charts are made from the data collected.

32. Experiment • In many experiments it is valuable to have a control. • A control is a standard for comparison. • In the salt lab the control is the room temperature water. It gives you something to compare the higher temperature water to. • In many experiments it is also important to have constants. Constants are the parts of the lab that remain the same for each sample being tested. • In the salt lab the volume of water, size of beaker and mass of the salt should all be constant.

33. Conclusion • Scientists take the data, analyze it and apply them to the hypothesis to form a conclusion • A conclusion is a judgment based on the information obtained • A hypothesis can never be proven. ..therefore scientists say the data supports the hypothesis or the data does not support the hypothesis

34. Theory • A theory is an explanation that has been supported by many, many experiments. • All theories are still subject to new experimental data and can be modified.

35. Scientific Law • Sometimes, many scientists over and over again come to the same conclusion about certain relationships in nature, for example: every time we drop something, it falls to the earth’s surface. • A scientific law is a relationship in nature that has been supported by many experiments and has not ever been refuted.

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37. Data Analysis • Suppose you get a call from a friend who lives in Canada. Your friend complains about how hot the weather has been lately and states the temperature has got up to 35! You think that figure must be wrong because 35 is cold! Actually, 35 can be hot or fold depending on which temperature units are used! • For a measurement to be useful, it must include both a number and a unit

38. SI Units • Measurement is a part of daily activities. Hospitals record the weight and length of each baby. Meters on gasoline pumps measure the volume of gas sold, the highway sign gives a measured distance from you to a different location…

39. SI Units • In the United States measuring something in miles, feet, ounces and in Fahrenheit is very common. But almost every other country in the world uses the metric system that includes meters, liters and Celsius. • The metric system was originally called systemeInternationaled’Unites, which was abbreviated SI

40. Base Units • There are seven base units in SI • A base unit is a defined unit in a system of measurement that is based on an object or event in the physical world. • Time, length, mass, temperature, amount of a substance (mole), electric current and luminous intensity

41. Time • The SI unit for time is the second • Time is measured by the frequency of microwave radiation given off by a cesium-133 atom • Time is the only part of the metric system that isn’t measured in 10’s

42. Time • 60 seconds = 1 minute • 60 minutes = 1 hour • 24 hours = 1 day • 365.25 days = 1 earth year

43. Length • The SI base unit for length is the meter • A meter is the distance that light travels through a vacuum in 1/299792458 of a second • A meter stick is helpful for measuring a room, kilometers are used to measure larger distances and centimeters and millimeters are used to measure smaller distances

44. Mass • Recall that mass is a measure of the amount of matter. • The SI base unit for mass is the kilogram • A kilogram is defined by the platinum-iridium metal cylinder kept in a triple bell jar in France. It is the only unit whose standard is a physical object • Most laboratories used grams or milligrams

45. Prefix practice

46. Temperature • The temperature of an object is a measure of how hot or cold the object is relative to other objects • Hot and cold are qualitative terms • For a quantitative description of temperature you need a measuring device. • Temperature is measured using a thermometer

47. Temperature • In a thermometer, a liquid expands when heated and contracts when cooled. The tube that contains the liquid is narrow so that small changes in temperature can be detected • Scientists use two temperature scales, Celsius and Kelvin

48. Temperature • In Celsius freezing point is 0⁰ and boiling point is 100⁰ • Kelvin is the SI base unit for temperature. • Kelvin is easy to calculate. In Kelvin freezing is 273 and boiling is 373. • To convert Celsius to Kelvin all you have to do is add 273 to the Celsius number. • Example: • What is -39⁰C in Kelvin? • -39⁰C +273= 234K • To convert from Kelvin to Celsius, you just subtract 273.

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50. Derived Units • Not all quantities can be measured a base unit. For example the SI unit for speed is meters per second (m/s). Notice that meters per second includes two SI base units- the meter and the second.