the ice cube or the puddle of water formed from it?
TRANSCRIPT
What has the greater mass?The ice cube ORthe puddle of water formed from it?
DEMONSTRATION
Prelab Title: The Mass of Dissolved SaltPurpose: To determine if a change in mass
occurs when salt dissolves in water.Hypothesis: If, then…. WHY?Materials:
salt (NaCl) watervial weighing paper
paper towel balance
Procedure:1. Fill vial 1/3 full of water. 2. Get a square of weigh paper and fold it into fourths.3. Mass the square of weigh paper on digital scale.4. Using the spatula/spoon, slowly add 0.50g – 1.00g of
salt onto the piece of weighing paper. 5. Place the vial containing the water on the balance with
the weighing paper and salt. Record the mass.6. Pour the salt into the vial containing the water. (Be
careful not to spill any salt). 7. Swirl gently. Be careful not to spill any water8. Mass the vial with the salt water and the weighing
paper. Record the mass.9. Take salt water to back sink. CLEAN AND DRY IT!!!!
DATA TABLEMass of system before dissolving _______gMass of system after dissolving _______gChange in mass ( )D _______g
“System” is made of _______, _______, ________, and _________.
Calculation: D = (Mass after) – (mass before) = mf - mi
Class Data Table (B)# D mass (g) # D mass (g) 1. 0.04 9. 0.292. 0.01 10. 0.303. 1.04 11. 0.294. 0.07 12. 0.785. 0.00 13.6. 0.02 14.7. 0.03 15.8. 0.45 16.
Class Data Table (C)# D mass (g) # D mass (g) 1. 0.00 9. 0.032. 0.10 10. 0.003. 0.00 11. 0.004. 0.06 12.5. 0.18 13.6. 0.00 14.7. 0.07 15.8. 0.39 16.
Class Data Table (A)# D mass (g) # D mass (g) 1. 0.44 9. 0.392. 0.10 10. 0.003. 0.12 11. 0.084. 0.04 12.5. 0.34 13.6. 0.04 14.7. 0.38 15.8. 0.00 16.
Qualitative Data (Observations)You should have AT LEAST three…
1.2.3.
Research Questions w/ Answers
1.2.3.4.5.
ConclusionTo determine if there is a change in mass
when salt dissolves in water, I…(Don’t forget to tell me if there is a mass change)
DEMONSTRATION
What has the greater mass?The bag before the reaction of vinegar + baking soda OR after the reaction?
The Law of Conservation
of Matter
We’ve talked about changes in matter…The evaporation of a puddle of waterRust forming on a metal fence
PHYSICAL
CHEMICAL
How did scientists come up with this law?
Just like we did with the vinegar and baking soda in a bag!
They measured the mass of the reactants (vinegar and baking soda) and then, after the reaction took place, they measured the mass of the products (reactants + carbon dioxide)
The Law of Conservation of Matter
During a chemical reaction, matter cannot be created or destroyed.
Even though the matter may change from one form to another, the same number of atoms
exists before and after the change takes place!
Since the overall mass of the matter does not change…
Mass of Reactants
Mass of Products
An Example of the L.C.M.Test tube containing
lead nitrate is placed upright in a flask that contains potassium iodide.
What are these?REACTANTS!
They don’t mix!
A stopper is put in place to create a closed system – an environment where matter cannot enter or escape.
The mass of the system is found.
After the mass is found, the system is turned upside down so the lead nitrate can mix with the potassium iodide.
They create lead iodide and potassium nitrate.
Although the matter changed in form, the total mass of the system remains unchanged.
The Formation of RustIron
Hard, gray-colored metal
RustFlaky, orange-red solid
When iron reacts with oxygen in the air, they form rust or IRON OXIDE.
This is written as:Iron + Oxygen Iron Oxide
Determining the Mass of Reactants and ProductsREMEMBER: The mass of the reactants is always equal
to the mass of the products.
Mass of Reactants
Mass of Products
Example: Tin FluorideTin + hydrogen fluoride -> tin fluoride +
hydrogen
What’s the total mass of the reactants?158.72 g
So what should the mass of the products be?158.72 g
118.7 g
40.02 g
Total Mass of Reactants: 158.72 g
Tin + hydrogen fluoride -> tin fluoride + hydrogen
If we know the mass of the tin fluoride, can we figure out how much hydrogen was produced?Subtract the mass of one product from the total
mass.
156.71 g
2.01 g
ANY QUESTIONS?
What is the final mass of the ice?