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Chemical Reactions. http://www.chem.wisc.edu/deptfiles/genchem/demonstrations/Gen_Chem_Pages/22organicpage/dehydration_of_sugar_by_su.htm. Today’s Lesson. Quick Recap Speeding Up Chemical Reactions Simple Experiment Study Guide Questions. Quick Recap.
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Chemical Reactions http://www.chem.wisc.edu/deptfiles/genchem/demonstrations/Gen_Chem_Pages/22organicpage/dehydration_of_sugar_by_su.htm
Today’s Lesson • Quick Recap • Speeding Up Chemical Reactions • Simple Experiment • Study Guide Questions
Quick Recap • Below is a quick recap from the previous lessons: • An atom can have Protons (+ charge), Neutrons (no charge) and electrons (- charge) • The Atomic Number tells us the number of protons and electrons in an atom • The Atomic Mass – Atomic Number = Number of electrons • Protons and neutrons go in the nucleus or middle of the atom. Electrons go in the electron shells.
Continued • Electron Shells: • 1st shell: up to 2 electrons • 2nd shell: up to 8 electrons • 3rd shell: up to 18 electrons unless it’s the last shell. Then it’s 8 • 4th shell: up to 32 electrons unless it’s the last shell. Then it’s 8. • The Group (up-down) tells us how many electrons are in the outer shell of that atom. • The Period (across) tells us how many electron shells there are.
Cations • An Ion is an atom that has gained or lost electrons to have a full outer shell. • Elements from Group 1, 2 & 3 normally lose electrons and will have more protons than electrons. As such, they have a positive charge. They are called cations. • Ions in Group 1 are charged +1 • Ions in Group 2 are charged +2 • Ions in Group 3 are charge +3
Anions • When a metal and a non-metal bond together, it’s called an ionic bond. They gain or donate electrons – they do not share them. • Elements from Group 5, 6 & 7 normally gain electrons and will have more electrons than protons. As such, they have a negative charge. They are called anions. • Ions in Group 7 are charged -1 • Ions in Group 6 are charged -2 • Ions in Group 5 are charged -3
Speeding Up Reactions • Speeding up reactions are quite important. If we don’t, then it may take too long for the reaction to occur. Some ways to increase the speed of a reaction includes: • Change temperature (normally increasing it) • Change the concentration of the reactant (ingredient not product) • Increase surface area • Helper Chemicals (catalyst)
Change Temperature • Today, we are going to start looking at how temperature can change reaction rates. • When you increase the temperature, it can speed up physical and chemical reactions. • This is due to particles moving more quickly due to a higher temperature. • If the particles move more quickly, they are more likely to collide and speed up the reaction.
Simple Experiment • You will need: • Hot Plate • 250 mL beaker • Spatula • 25 mL of water accurately measured • Sugar • Heat Probe • Logger Pro
Preliminary Questions • Please answer these questions in your Science book: • We are going to dissolve sugar into 25 mL of water at different temperatures (20, 40 & 80C). Make a hypothesis on which one will dissolve the most sugar along with how many spatula’s of sugar it will dissolve. • How can we accurately measure the amount of sugar put into the beaker so we put in the same amount each time along with making sure all the sugar is dissolved before adding more. • Give some suggestions on what we can do to make this experiment as accurate as possible.
Method • Measure 25 mL of water into a beaker. Heat to 20 C with a hot plate. • Add 1 spatula full of sugar at a time. Keep adding spatula’s of sugar until no more will dissolve. Record how many spatula’s have been dissolved. • Repeat for 40 C & 80 C water. • What could the logger pro equipment be used for?? Hint hint…
Questions • Please answer these questions in your Science book: • What pattern did you notice in the amount of sugar that was dissolved in the 25 mL’s of water? Explain. • Was there any possible errors in our results? How could these errors be minimized or removed? • Did you add any extra instructions to the method to improve it? If you did, include them here. • If we want to dissolve more solid into water, how could this be done? Try and explain using the particle model. • What problems might we have if we try and dissolve solids in water at 100C? Explain why.
