Introduction to chemistry Unit 1 Introduction to chemistry

Well… What is chemistry? First, we need to think about what science is. Right now as you sit in my class, your tummy is making a weird sound. What is that sound? Why is it happening? What can you do to stop the sound?

Science helps us solve problems! So, your tummy noise is a problem. It is a problem that needs to be solved! But you are a scientist, so lets solve it with science! Problem: Tummy Noise Hypothesis: If I eat a cookie, then my tummy will stop making noise Experiment: 1. Record the number of tummy noises over 1 minute 2. Eat cookie 3. Wait 15 minutes 4. Record the number of tummy noises over 1 minute 5. Compare data Data: Tummy made noise 4 times in one minute before cookie and 0 times in one mintute after cookie Conclusion: Eating the cookie reduced/eliminated the number of tummy noises. Therefore, tummy noise was due to empty stomach/hunger. Eating a cookie filled stomach/eliminated hunger. Elimination of hunger reduced/eliminated tummy noise. Hypothesis was correct.

Science: the knowledge obtained by observing natural event and conditions in order to discover facts and formulate laws or principles THAT CAN BE VERIFIED AND TESTED Chemistry: the study of the composition, structure, and properties of matter, the processes that matter undergoes, and the enrgy changes that accompany these processes Chemistry is a branch of SCIENCE

So….. If we use science to help us understand the world around us and formulate testable explanations, what types of problems/observation might CHEMISTRY help us solve/make?

Branches of Chemistry Organic Chemistry: the study of compounds containing carbon Inorganic Chemistry: the study of compounds not containing carbon Physical Chemistry: the study of the properties and changes of matter and their relation to energy Analytical Chemistry: the identification of the components and composition of materials Biochemistry: the study of substances and processes in living things

Practical Application: What do we DO with it? Chemical: any substance that has a definite composition. Basically, THAT’S EVERYTHING! Water is a chemical! If someone ever tells you they are on a ‘chemical-free’ diet, they will die. Help them. All food is made up of chemicals! So great. Everything is chemicals. But what do we do with that knowledge? How do we study chemistry?

Research Basic Research: to increase knowledge Can you think of any examples where you were asked to conduct basic research? Applied Research: to solve a problem Can you think of any examples where you were asked to conduct applied research? Technology Development: Production and use of products that improve our quality of life Can you think of any examples of technology development in chemistry?

Real World Chemistry! Chemistry helps us understand our world! Chemistry is not just in the LAB! Chemistry is used to solve REAL WORLD PROBLEMS! Chemistry is used to develop NEW AN IMPROVED products! Chemistry is an old science, but it isn’t dead! Fields such as forensic chemistry and green chemistry are changing our world today!

Matter and Its Properties Mass: a measure of the amount of matter: How much STUFF there is…this is different from WEIGHT. How??? Matter: anything that has mass and takes up space Can you think of a situation in which the mass of an object might change? Can you think of a situation in which the composition of the matter of an object might change?

Atoms are the building blocks of matter Atom: the smallest unit of an element that maintains the chemical identity of that element. Element: a pure substance that cannot be broken down into simpler, stable substances and is made of one type of atom. One atom of CARBON is still CARBON. You can break it down further, but it’s not CARBON anymore! Why isn’t water an element?

All substances have characteristic properties Extensive properties: depend on the amount of matter present. Ex: Volume, mass, amount of energy Intensive properties: do NOT depend on the amount of matter present. Ex. Melting point, boiling point, density, conductivity Intensive properties are the same for a given substance REGARDLESS of how much is there!

Physical Properties and Physical Changes Matter can change. Can you think of some ways in which matter might change? Physical Property: a characteristic that can be observed or measured without changing the identity of the substance melting point, boiling point, density Physical Change: A change that does not involve a change in the identity of a substance cutting, melting, boiling

States of matter Matter can change state. This is an IMPORTANT physical change! Water can change from solid-liquid-gas Change of state: a physical change of a substance from one state to another. 3 common states of matter on this planet are solid, liquid, and gas. THERE ARE OTHER STATES! My new fav is time crystals….although it’s not as cool as it sounds

Solid: matter in the solid state has definite volume and definite shape. The particles are packed tightly together and there are strong attractive forces. The particles of a solid can only vibrate. Some solids have higher degrees of attraction between its particles so its particles are more easily compressible. Why do you think some metals are easily bendable? Liquid: has a definite volume, but no definite shape Gases: has no definite volume or definite shape What can you say about the attractive forces within the particles of a liquid? A gas? WHY?????? Plasma: a physical state of matter in which atoms lose most of their electrons

Energy and changes in matter Energy flows Knowing this, describe the energy flow in the following changes: Solid-liquid (melting) Liquid-gas (vaporizing) Gas-liquid (condensing)

Chemical properties and Chemical Changes Chemical property: relates to a substance’s ability to undergo changes that transform it into different substances Reactivity, flammability Chemical Change: also called a CHEMICAL ReACTION A change in which one or more substances are converted into different substances The substances that you start with are called the REACTANTS (They REACT together) The substances that are formed are called the PRODUCTS (They are PRODUCED)

Matter can be a pure substance or a mixture Pure substance: composition is the same throughout Mixture: a blend of two or more kinds of matter, each of which retains its own identity and properties

MIXTURES Mixture: a blend of two or more kinds of matter, each of which retains its own identity and properties. The composition MUST be specified. Often done in percentage Homogeneous mixtures: uniform in composition. ALSO CALLED SOLUTIONS!!!! You can’t ‘see’ the different parts Heterogeneous mixtures: not uniform in composition. You can ‘see’ the different parts Mixtures can be separated using physical properties/changes

Pure substance Pure substance: have a fixed composition, always homogeneous, cannot be broken down and retain the properties of the substance elements or compounds What happens if you break down a pure substance????

ELEMENTS! In general, the properties of the element are predictable when they are arranged on the periodic table Groups/Families: vertical columns some have special names group 1 (1a): alkali metals group 2 (2a): alkaline earth metals group 17 (7a): halogens group 18 (8a): noble gases Elements in the same group/family have similar properties Periods: horizontal rows Lanthanide and Actinide series: don’t really follow this predictable pattern, so they are set below the other elements

Metals, nonmetals, metalloids Metals, to the LEFT of the ZIGZAG line most metals are solids at room temperature, good conductors of heat and electricity, are generally malleable (hammered into sheets), generally ductile (drawn into wires), and generally have a high tensile strength (can be pulled without breaking) Nonmetals, to the RIGHT of the zigzag line poor conductor of heat and electricity Metalloid, generally ON the zigzag line have properties of metals and nonmetals

Compounds! Compound: chemical combination of one or more elements How do we represent a compound? Symbol and subscript tell the numbers and types of atoms present Elements and compounds can only be broken down by chemical changes! When you break a compound or element, you end with a NEW SUBSTANCE!