Chemical and physical changes
Is cutting a paper a physical or a chemical change?
It's a physical change.
Is an apple rotting a chemical change? how do you know?
yes! color change, irreversible.
What is a chemical reaction?
A chemical reaction is a process in which one or more substances, the reactants, are converted to one or more different substances, the products.
bonds broken and/or formed, atoms rearranged.
True or false: The formulas of the reactants appear to the right of the arrow.
False: The formulas of the reactants appear before the arrow.
What is the law of conservation of mass?
Matter cannot be created or destroyed.
Is melting water a physical or a chemical change?
It's a physical change.
How do you know a chemical reaction occurs when bleach gets on your clothes?
color change
irreversible
What are the products?
How many Hydrogen atoms in the products?
NaOH + HCl --> NaCl + H2O
Products: NaCl + H2O
2 H atoms
46 g of sodium react with bromine to produce 206 g of sodium bromide. How much bromine has reacted?
46g Na + ____g Br --> 206g NaBr
160 g
Is mixing vinegar and bicarbonate a physical or a chemical change?
It's a chemical change
How do you know a chemical reaction occurs when you burn paper?
color change, temp change, gas (smoke)
Decide which are the reactants and which are the products in the following reaction: Hydrogen reacts with nitrogen to produce ammonia.
The reactants are hydrogen and nitrogen and the product is ammonia.
What do we use to separate the formula of one reactant from the formula of other reactant?
The formulas are separated with a plus sign.
46 g of sodium react with 73 g of hydrogen chloride to produce 117 g of sodium chloride and hydrogen. How much hydrogen has been produced?
46g Na + 73g HCl --> 117g NaCl + _____ g H
2 g
Is mixing salt and water a physical or a chemical change?
It's a physical change
Name 4 signs of a chemical change
1. unexpected color change
2. unexpected temperature change
3. gas bubbles
4. precipitate
What is the difference between a chemical reaction and a chemical equation?
A chemical equation is the representation of a chemical reaction.
What are the reactants?
List the number of types of atoms in the reactants.
2Fe2O3 + 3C --> 4Fe + 3CO2
Reactants: 2Fe2O3 + 3C
4 Fe
6 O
3 C
Fill-in the blanks: According to the law of conservation of mass, chemical reactions do not _________ or ________ matter, they only _____________ matter. Therefore, the mass of the _____________ is equal to the mass of the ____________
According to the law of conservation of mass, chemical reactions do not create or destroy matter, they only rearrange matter. Therefore, the mass of the reactants is equal to the mass of the products.
What is the main difference between a physical and a chemical change?
Physical changes do not produce new substances while chemical changes produce new substances.
Why does cake batter rise in the oven?
Describe the two types of reactions we learned about and give an example of each.
endothermic: takes in energy, cold, ice pack
exothermic: releases energy, hot, steel wool and copper sulfate
How many Carbon atoms in the products?
Is it balanced?
CH4 + 3O2 --> CO2 + 2H2O
2 carbon atoms
No! 6 oxygen atoms in the reactants, 2 in the products
Is this balanced?
2NH4 + CuSO4 → (NH4)2SO3 + Cu
No! There are 4 oxygen atoms in the reactants and 3 oxygen atoms in the products