Law of Conservation of Mass Essential Lab

Catalyst1. Classify the following as an element,

compound or mixture:

a) Baking soda

b) Carbon

2. Classify each of the following as a homogeneous or heterogeneous mixture

a) Mouthwash

b) Ice cubes in water

SWBAT apply the law of conservation of mass to chemical and physical changes

Agenda

• We do: Lab setup (10 min)• You do: LoCM Essential Lab (60

min)• I do: Law of Conservation of Mass

Mini lesson (10 min)• You do: data analysis and

conclusion (10 min)

HOW IS MASS AFFECTED DURING A CHEMICAL AND PHYSICAL CHANGE?

LET’S FIND OUT!

Essential Lab• You will be performing physical and

chemical changes on different substances and measuring the mass before and after the change– Formation of a precipitate– Crushing smarties– Melting ice– Baking soda and vinegar– Dissolving sugar– Dissolving Alka-seltzer

Conservation of Mass Lab• You will need to write a complete lab report, with

all of the components from the ETO lab template– Cover page– Title– Introduction– Problem statement– Hypothesis– Materials – Procedures (1-2 sentences for each table)– Variables– Data – Data analysis– Conclusion

Lab Setup• Leave a space in your notebook for the

cover page, title and introduction• Write down the problem statement,

hypothesis, materials and variable– Problem Statement: How is the mass of

matter affected if it undergoes a physical or a chemical change?

– Hypothesis: How do you think the mass of the matter will be affected after the change? Will it increase, decrease or stay the same? WHY?

– Variables: IV, DV, Control, Constant

Lab Data and Calculations

• Data tables (6 total) = ‘change in’

• Particle level representation (6 total)• Is this a physical or a chemical change?• How would particles look with a physical or

a chemical change?

You have 8 minutes at each station• USE YOUR TIME WISELY• Lab group roles

• Project director = makes sure group is on task and on time

• Technical manager = performs all the measurements on the balance

• Materials manager = organizes and cleans materials before moving to the next station

• Safety director = keeps track of time, assists materials and project director

Lab Expectations

• You will clean the materials when you are asked to do so

• You will rotate to the next station when you are asked to do so

• You will not leave your station unless you are the technical director

• You will not talk to other lab groups• You will not prevent other groups from going to

a station because you did not use time wisely and did not finish

LABS ARE A PRIVLEDGE

• If you are not following lab expectations you will be given a data sheet and asked to complete the lab from your seat.

WHAT WERE YOUR RESULTS? WAS YOUR HYPOTHESIS SUPPORTED?

Law of Conservation of Mass

Mass cannot be created or destroyed, it can only be converted

State the Law. Equation

In a Picture Common Misconception

In any physical or chemical reaction, the

total mass is conserved or does not

change.

massreactants= massproducts

Mass does not change even if the

substance changes to a new phase.

Law of Conservation of Mass

Other ways to say “conserved”

• Saved• Keep• What goes in must come out• Reactants equal products • Remains• massreactants= massproducts

Data Analysis and Conclusion• Make sure you have a data table

and particle level representations for ALL six parts

• Answer the ‘DATA ANALYSIS’ part with complete sentences

• Answer all 7 conclusion questions (minimum 3 paragraphs)

• Complete lab report as homework – due next class

Extra Problem

Magnesium reacts with oxygen to produce magnesium oxide. If 2.4g of magnesium reacts to make 2.9g of

magnesium oxide, how many grams of oxygen react?

Extra Problem

• Donald does a reaction in which he mixes 40 grams of sodium hydroxide with 32 grams of another chemical. After the reaction has completed, he is left with a precipitate that has a mass of 18 grams. How much gas was released in this reaction?

Another way to say mass is conserved is to say that the mass of the reactants equals the

mass of the prodcuts

Extra Problem

50 grams of sodium reacts with chlorine to form 126 grams of salt. How many grams of

chlorine reacted?