Law of Conservation of Matter

Changes of Matter &

The Law of Conservation of Mass

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​There are two types of changes in matter; physical change and chemical change. As the names suggest, a physical change affects a substance’s physical properties and a chemical change affects its chemical properties.

​

• ​occur when there is a change to one or more physical properties

• ​does not result in a change in chemical identity

• are reversible​ in many cases

​

Physical Changes

• occur when one substance changes into another​ after a chemical reaction

• ​"ingredients" are called reactants and end results are called products

• irreversible​

Chemical Changes

Multiple Choice

A physical change...

• changes the physical properties of an object, but does not create a new substance.

• creates a new substance and cannot be undone.

Multiple Choice

A chemical change

• changes the physical properties of an object, but does not create a new substance.

• creates a new substance and cannot be undone.

• Production of gas/bubbles​

• Production of odor

• Change in color

• Formation of precipitate

• Exothermic/Endothermic reaction

• ​Release of light

​

Identifying chemical changes

​Signs of a chemical change

​

Chemical reactions tend to happen more quickly at higher temperatures. When temperatures are higher, atoms and molecules have more kinetic energy which enable them to move around and rearrange more quickly and easily.

Multiple Choice

What kind of change occurs if matter changes in amount, size, or shape?

• substance change

• chemical change

• physical change

• elemental change

Multiple Choice

Which of the following is NOT an example of a physical change?

• Smashing a soda can

• Wood breaking apart

• Salt dissolving in water

• Iron rusting

Multiple Choice

A change where one or more new substances are created.

• Physical Change 
• Chemical Change 

Multiple Choice

Which of these is a result of a chemical change?

• A mixture
• A solution
• A new substance
• Melting or freezing

Multiple Choice

Which of the following is a sign that a chemical reaction has occurred?

• change in shape
• melting
• formation of a gas
• dissolving

Multiple Choice

Physical or Chemical Change?  Baking a cake.

• Chemical Change
• Physical Change

Multiple Choice

Which of the following is NOT an example of chemical change?

• sour milk

• burning wood

• breaking a pencil

• rust

Match

Match the following

Chemical

Chemical

Physical

Physical

Chemical

• Chemical

• Chemical

• Physical

• Physical

• Chemical

This law states that mass cannot be created or destroyed during a physical or chemical change. The mass you have before the change is always equal to the mass after the change. For example, a chemical reaction between 93g of mercury and 7g of oxygen will produce 100g of mercuric oxide.

The Law of Conservation of Mass

Multiple Choice

Which of the following describes the law of conservation of mass?

• In a reaction, atoms are created or destroyed.

• In a reaction, atoms are not lost or made.

• In a reaction, the mass of the product may be more or less than the reactants.

• In a reaction, mass never stays the same.

Multiple Choice

Matter can not be created nor destroyed: it can only be

• Destroyed a little bit

• Invisible

• Transformed, changed

• None of the above

Multiple Choice

If reaction starts with 20g of reactants it should produce 

• a total of 40g of products

• a total of 10g of products

• a total of 80 g of products

• a total of 20g of products

Multiple Choice

What is the reactant in the following equation?2NaHCO₃  -> Na₂CO₃  +  CO₂  + H₂O

• NaHCO₃

• Na₂CO₃

• CO₂

• H₂O

Multiple Choice

According to the Law of Conservation of Mass, what happens to the wood and oxygen when it is burned?

• The wood disappears.

• It stays the same chemically.

• The atoms in the wood and oxygen rearrange and form smoke and ash.

• Nothing.

Multiple Choice

The number to the lower side of an element is a 

• Charge

• Coefficient

• Superscript

• Subscript

Multiple Choice

The number in front of a compound or element is a 

• Subscript

• Coefficient

• Superscript

• Charge

Labelling

Label the following equation.

Drag labels to their correct position on the image

Subscript

Yield

Reactants

Coefficient

Product

Poll

Which level best describes where you are at the end of this lesson?

• Level 1 - I need help to differentiate between physical and chemical changes

• Level 2 - I am able to differentiate between physical and chemical changes; as well as give examples on my own

• Level 3 - In addition to performing tasks at level 2, I can also describe how temperature affects chemical changes

• Level 4 - Not only can I perform level 3 tasks, I can also demonstrate that mass is conserved when substances undergo physical and chemical changes.