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?