Types of Changes
What type of change is melting ice?
Physical
What are starting substances called?
Reactants
What does the arrow in an equation mean?
React to form/produce
What is conserved in a chemical reaction?
Mass
What does a subscript show?
Atoms per molecule
What is one sign of a chemical change?
Gas produced
What are ending substances called?
Products
Write the word equation for H₂ + O₂ → H₂O
Hydrogen + oxygen → water
What type of system prevents matter escaping?
Closed system
In H₂O, how many hydrogen atoms?
Two
Does dissolving salt in water cause a chemical change?
No
In the reaction: Mg + O₂ → MgO, what is the product?
Magnesium oxide
Convert: Sodium + chlorine → sodium chloride
Na + Cl₂ → NaCl
True/False: The mass of products must equal reactants
True
In 3H₂O, how many oxygen atoms?
Three
What occurs to atoms during a chemical change?
Rearranged
What is the product of HCl + NaOH?
Salt and Water
CH₄ + O₂ → CO₂ + H₂O - name the products
Carbon Dioxide and Water
Balance: H₂ + O₂ → H₂O
2H₂ + O₂ → 2H₂O
In CH₄ + 2O₂ → CO₂ + 2H₂O, how many total hydrogen atoms?
Four
Is burning paper chemical or physical? Why?
Chemical – new substance
What is the product when methane combusts?
Carbon dioxide and water
State the chemical equation for: Magnesium + HCl → Magnesium chloride + hydrogen
Mg + 2HCl → MgCl₂ + H₂
Why must we balance chemical equations?
Conserve atoms
In 2NH₃, how many nitrogen and hydrogen atoms total?
Two nitrogen, six hydrogen