1. The word 'pure' is used in chemistry in a different way from its everyday meaning. For example, shops sell cartons labelled as 'pure' orange juice. The label means that the contents are just orange juice, with no other substances added. However, the juice is not pure in the chemical sense because it contains different substances mixed together. In chemistry:a pure substance consists only of one element or one compound
a mixture consists of two or more different substances, not chemically joined together
a pure substance consists only of one element or one compound
a mixture consists of two or more different substances, not chemically joined together
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Question 2
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Name at least 3 different pure substances that you know of.
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Question 3
3.
Learning Objectives:
● Describe the process of solution formation for salts versus molecular compounds.
● Identify the differences in an ionic solution and a molecular solution
1. Move the conductivity tester to the solution.
2. Shake some salt into the water.
3. Answer the questions below
A. Does the conductivity tester light up?
B. What kind of substance causes the conductivity tester to light?
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Question 4
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3. In the simulation above, click on the “remove salt” button.
4. Change the solute to sugar and shake some into the water.
5. Answer the questions below
C) Did it light up?
D) What type of substance is this?
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Question 5
5.
6. Click on the “Micro” tab at the top of the page.
7. Select the sodium chloride solute.
8. Shake some salt into the water.
9. Answer the question
E) What happens to the salt as it mixes with the water?
9. Look at the Concentration graphic.
F) How do the concentrations of the 2 ions compare?
G) How would the concentrations of the cation (postive ion) and anion (negative ion) compare if the salt had been CaCl2 ?
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Question 6
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10. Now move the evaporation slider to the right and hold until all the water has evaporated.
H) What happened to the concentration of the ions as the water evaporates?
I) What do you observe?
J) Is the substance, NaCl, different than when it was first added to the water?
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Question 7
7.
11. Click the reset button at the bottom.
12. Select the solute sucrose.
13. Add the sugar to the water
K) What do you observe?
L) Which solution results in a greater number of particles in solution- salt or sugar?
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Question 8
8.
14. Use the slider at the bottom to evaporate the water.
M) What did you observe? How is the formation of sugar crystals different from the formation of salt crystals?
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Question 9
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15. Now, click on the “Water” tab at the top. Water is the molecule H2O
N) What do the RED spheres represent?
● What do the WHITE spheres represent?
● Is the molecule symmetrical?
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Question 10
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17. Click and drag a sodium chloride crystal into the water. Immediately click the “pause” button in the lower left.
18. Notice that the water molecules surround the ions. This process is called hydration.
O) Which end of the water molecules seem to face the Na+ ion- the red end or the white end?
P) Is this end more positive or more negative?
Q) Which end of the water molecules seems to face the Cl- ion? Is this end more positive or more negative?
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Question 11
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19. Click the reset button.
20. Repeat the process for glucose.
R) Does the sugar molecule break up?
S) Do the water molecules orient themselves in any particular way?
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Question 12
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21. Click on the “Sugar in 3D” button.
T) Is the sugar molecule symmetrical? Describe what you looking at in terms of the sugar molecule