Chemical & Physical Changes
A type of change that results in the formation of a new substance with different properties.
What is a chemical change?
What is the law of conservation of mass?
Matter cannot be created or destroyed in a chemical reaction.
The number of oxygen atoms in one molecule of glucose (C₆H₁₂O₆).
What is 6?
The speed at which reactants turn into products.
What is the rate of reaction?
Which of the following reactions is endothermic?
A. Ice melting
B. Wood burning
C. Water freezing
D. Rust forming on iron
Ice melting is an example of an endothermic reaction.
Melting ice or breaking a glass are examples of this type of change.
What is a physical change?
Substances that are transformed into new products during a reaction.
What are reactants?
The number of nitrogen atoms in one molecule of ammonia (NH₃).
What is 1?
Increasing this property of a solid increases the rate of reaction by allowing more collisions.
What is surface area?
How is energy absorbed in an endothermic reaction?
Energy is taken in from surroundings to break bonds.
This is a physical change:
A. Burning paper
B. Dissolving sugar in water
C. Rusting iron
D. Baking a cake
What is dissolving sugar in water?
Magnesium reacts with oxygen to form this compound.
What is magnesium oxide?
The total number of atoms in one molecule of aspirin (C₉H₈O₄).
What is 21?
Raising this environmental factor speeds up most reactions.
What is temperature?
Identify endothermic and exothermic from energy profile diagram.
Endothermic: energy of products > reactants;
Exothermic: products < reactants.
Boiling water represents this kind of change.
What is a physical change? (no new substance is formed)
In a closed system, this happens to the total mass during a reaction.
What is it stays the same (or is conserved)?
The balanced form of Na + Cl₂ → NaCl.
What is 2Na + Cl₂ → 2NaCl?
How does increased concentration affect reaction rate?
More particles in the same space increases collision frequency and reaction rate.
Temperature change in exothermic reaction?
Temperature of surroundings increases (heat is released).
During a chemical reaction, this property of matter is conserved.
What is mass?
The balanced form of Fe + O₂ → Fe₂O₃.
What is 4Fe + 3O₂ → 2Fe₂O₃?
Aluminum (Al) and copper sulfate (CuSO₄) react to form aluminum sulfate (Al₂SO₄) and copper (Cu); this is the balanced equation.
What is 2Al + 3CuSO₄ → Al₂(SO₄)₃ + 3Cu?
What is collision theory? (3 points)
The theory that explains reactions occur when particles collide with sufficient energy and correct orientation.
Define endothermic and exothermic in terms of energy and bonds.
Endothermic: energy absorbed, bonds broken; Exothermic: energy released, bonds formed.