Law of Conservation of Mass
What is the Law of Conservation of Mass and why is it important for us to understand it?
Matter cannot be created or destroyed in a closed system, only rearranged. It is important for us to understand that substances on Earth do not just disappear, but are rearranged into new products
What is the smallest unit of matter?
The Atom
A pure substance made up of only ONE type of atom is known as a(n)...
Element
Physical: Change in state, size, or shape, but substance retains the same identity
Chemical: New substance is formed.
The compounds on the right side of the arrow are known as __________ while compounds to the left of the arrow are known as ___________
Products, Reactants
Describe the major differences between an open system and a closed system. Also include how each system affects the mass of a substance after a chemical reaction.
Open= Matter can enter and exit
Closed: No matter can come in or go out
open systems tend to have less mass due to gases being able to escape into the atmosphere.
List all of the subatomic particles in an atom with their respective charges and location within the atom.
Proton, Positive, Nucleus
Neutron, Neutral, Nucleus
Electron, Negative, Electron Cloud
Compare and Contrast Homogeneous and Heterogeneous Mixtures. Give a real-life example of each to support your answer.
Homogeneous= looks the same throughout
Heterogeneous= looks different throughout. Examples may vary
Describe one chemical and one physical change that you might see at a hair salon.
Physical: Cutting Hair
Chemical: Coloring/Bleaching hair
Large numbers in front of compounds are known as _______ while small numbers to the right of elements are known as ________
Coefficients. Subscripts
In a open system, a student burns a piece of wood and observes that the mass of the remaining ash is much less than the original wood. They claim that mass was lost. How would you explain what happened using the Law of Conservation of Mass?
The mass was not lost, the atoms of the reactants were just rearranged to form new products with different properties. Some of the reactants during into gaseous products and left the system into the atmosphere, giving the illusion of lost mass.
An element with an atomic number of 12 and an atomic mass of 24.305. Calculate the number of protons, neutrons, AND electrons in the element.
Protons: 12
Electrons: 12
Neutrons: 24-12=12
What are the biggest differences between Compounds and Mixtures?
Compounds= made up strictly of elements, chemically bonded, fixed ratio
Mixtures= Physically combined, two or more substances, no fixed ratio.
List 3 pieces of evidence that prove a chemical reaction has taken place.
- Production of Gas, Production of Light, Temperature Change, Color Change, New Odor, New Substance
Count the number of individual elements on the product side of the reaction
Ca(OH)₂ + HCl → CaCl₂ + H₂O
Ca=1
Cl=2
H=2
O=1
Ashley is having a bonfire. She burns 8 logs to start. As the night goes on the pile of logs gets smaller and smaller until there is nothing but ash and some smoke. Ashley tells her mom that the logs magically disappeared since there is way less than she started with. Is Ashley correct in her thinking? Explain your reasoning.
Name 2 scientists who contributed to the Atomic Theory and explain their respective models of the atom.
Answers may vary
Identify the following as elements, compounds, or mixtures. If it is a mixture, identify if it is homogeneous or heterogeneous.
Water, Carbon Dioxide, Silver, Soil, Salt Water, Gold, Glucose.
CO2= Compound
Silver=Element
Soil= Heterogeneous Mixture
Salt Water: Homogeneous Mixture
Gold= Element
Glucose= Compound
Justify whether cooking an egg is a chemical or physical change by using scientific evidence.
Chemical due to the denaturing of proteins during high heat cooking.
Why do compounds have different properties than the elements they are made from?
When elements join together they must undergo a chemical change. We know that during chemical changes, new substances are formed which often look different than what we started with. Compounds have different properties because they are NEW SUBSTANCES.
A student conducts an experiment by mixing vinegar and baking soda in an open beaker. They observe bubbles forming and notice that the total mass of the system appears to decrease when measured on a scale.
🔹 Analyze the situation and explain why the measured mass seems to decrease.
🔹 Predict what would happen if the same reaction occurred in a closed container instead of an open one
Describe how the atomic model changed over time. How did we get to where we are today in terms of atom knowledge?
Answers may vary
List the chemical formula and elements involved for the following:
Water, Table Salt, Methane, Carbon Dioxide
Explain how the Law of Conservation of Mass applies to both physical and chemical changes. Provide an example for each to support your explanation.
Teacher Answer
A scientist discovers a new compound made of two elements. What tests could they perform to determine if the substance is truly a compound and not just a mixture? Explain your reasoning.
Answers may vary