Examples:
Is rust an example of a chemical change or physical change.
Chemical change
Explain what a physical and chemical change is and give an example of each.
physical change: a change that alters the form or appearance of a substance without changing it into a different substance.
Chemical Change: A change in matter that produces one or more substances.
What is a reactant? What is a product? Where do you see them in a chemical equation?
reactant: on the left side of equation- the substances before a chemical reaction
product: on the right side of the equation- the subtance(s) formed after a chemical reaction.
How do you know if a chemical equation is balanced or unbalanced?
same number of atoms is balanced
What is an atom? What does an atom look like in a chemical equation?
the basic unit of matter made up from elements. Example in equation: H, Na, Cl
Explain what a solvent and a solute is. Give an example of a solution that contains both, and identify each part of the solution.
solvent: part of the solution that is usually present in the largest amount.
solute: the part of the solution that is dissolved by the solvent
Lemonade, Water: solvent, lemonade mix: solute
Explain what endothermic and exothermic reactions are and give an example of each.
endothermic: more energy is released to break the bonds of the reactants that is released by the formation of the products
exothermic: the energy released as the products form is greater than the energy required to break the bonds of the reactants.
What are the subscripts and coefficients in a chemical equation? What do they tell us?
subscript: number that shows how many atoms of that element are in the molecule
coefficient: they balance the equation so the number of atoms in the reactants equal the number of atoms in the product.
Is this equation balanced? If not make it a balanced equation.
Fe2 O3 + C = Fe + CO2
no, 2Fe2O3 +3C = 4Fe + 3CO2
When energy is absorbed, it causes its surroundings to become cooler (the reaction feels cold)
What is an endothermic reaction
Why is baking a cake an example of a chemical change?
Once the cake is formed, we cannot get back the original batter. Also the chemical substances of the cake are different from the batter.
What is the best way to determine a chemical reaction has occurred? Give 3 indicators that a chemical reaction may have happened?
a new substance forms.
gas production, change in color, precipitate
What is the Law of Conservation of Mass and how does a balanced chemical equation show us its true?
matter is neither destroyed of created.. all atoms are present at beginning of chemical reaction are present at the end of the reaction. same number of atoms in reactants and products.
How many total oxygens are in this equation?
4Fe+2O3 -->2Fe2O3
12 total, 6 per side
2H2O + 3H2
5
Why is Digestion of food a chemical change?
There is a formation of a new substance. So, it is considered to be a chemical change.
What is an open and closed system and which is better to show the law of conservation? Explain why.
open system: where matter can enter and escape
closed system: traps the matter, including gas.
closed system
Describe the difference between an open system and a closed system
Open system- matter can enter and escape
Closed system- invisible gases cannot be moving in or out of the system
Is this equation balanced? What kind of chemical reaction is this?
3Ag2S + 2Al = 6Ag + Al2S3
yes, replacement
The energy is usually released as heat in this reaction (the reaction feels hot or warm)
What is exothermic reaction?
Explain how the process of boiling an egg can be both a physical change and a chemical change.
The egg becoming hard-boiled is a chemical change.
The water boiling is a physical change.
Describe why slicing pizza is a physical change but baking a pizza is not.
When you slice pizza... you still have pizza. (The substance doesn't change.)
When you bake pizza the individual ingredients that make up the pizza change into something else.
What are the reactants and products in the following equation? How many of each atom are there?
3Ag2S + 2Al -----> 6Ag + Al2S3
Reactants left
Products right
Is this equation balanced? If not make it a balanced equation.
Pb(NO3)2+ NaI = PbI2 + NaNO3
no, Pb(NO3)2+ 2NaI = PbI2 + 2NaNO3
How many atoms are in the following chemical equation? Is the equation balanced or not?
Zn+2HCl ----> ZnCl2+H2
10. Yes it is balanced.