Chemical Reactions Unit Review

Chemical Change Vs. Physical Change

100

If someone gets there haircut, is that an example of a chemical or physical change? 

A physical change. It is easily reversed into it's original form (the hair can grow back out!) 

200

Which of the following examples are examples of chemical changes? (There are more than one!)

1. Stepping on a soda can 

2. Rusting iron  

3. Cooking an egg

4. Cutting paper into pieces

Rusting iron and cooking an egg. These two examples are two that can not be easily reversed, and new substances are being formed. 

300

Is water evaporating into the air an example of a chemical change or a physical change? 

An example of a physical change! There is no new substance being formed, but rather a state change. Remember: if something is changing between a solid, liquid or gas, it is not becoming a new substance. 

400

Is melting ice an example of a chemical or physical change?

Physical! This is another example of a state change (solid to a liquid) and no new substance is being formed. 

Chemical Equations!

100

Fiona bakes a chocolate cake. To do so, she mixes together, eggs, chocolate, baking soda, flour, etc. Her end product was a chocolate cake. Identify which part(s) of this experiment are the reactants and which part(s) are the product. 

The reactants are the 'ingredients', so eggs, chocolate, baking soda, flour, etc. because these substances are being mixed together to form something new. 

The products are the 'end product' or the new substance being created. In this case, the chocolate cake. 

200

 ____SnO₂ +  ____H₂ --->  _____Sn +_____H₂O  

Which are the reactants and which are the products? 

SnO₂ +  H_{2 are the reactants and Sn + H2O are the products.} 

_{Remember, whatever is to the left of the arrow are always the reactants and whatever is to the right of the arrow are always the products.} 

300

What does it mean for a chemical equation to be balanced? 

To be balanced, a chemical equation needs to have the same number of atoms on either side of the equation. 

400

Is the following chemical equation balanced? 

Al + O₂ = Al₂O₃

No - it is not balanced. 

There are two aluminum atoms on the product side and only one of the reactant side. Similarly, there are three oxygen atoms on the product side and only two on the reactant side. 

Vocabulary and more

100

What does the subscript (or small number) tell us in a chemical reaction? 

The subscript (or small number) tells us how many individual atoms there are. 

200

What does the coefficients (big number) tell us in a chemical reaction?

The coefficients (big number) tell us how many molecules there are in that chemical equation. 

300

What is the difference between an endothermic and an exothermic reaction? 

An endothermic reaction is a type of chemical reaction that gets colder overtime. 

An exothermic reaction is a type of chemical reaction that gets warmer over time. 

400

What is the Law of Conservation of Mass?

The Law of Conservation of Mass states that mass can never be created or destroyed in any chemical reaction. 

Labs

100

Why might we wear gloves during a science lab?

Answers may vary: 

Some chemicals can be harmful to the skin causing burns or irritations. (Example: Calcium Chloride) 

200

What tool did we use to measure vinegar?

Graduation Cylinder. 

300

What tool did we use to measure how many grams of baking soda we needed?

A scale

400

True or False: you may never eat or drink while a lab is happening in science class. 

TRUE!