Open & Closed Systems
True or false. The following is the definition of an Open System- This system allows both matter and energy to exchange with its surroundings.
True
Define a Closed System.
A system that can exchange energy but not matter with its surroundings.
What happens to molecules and atoms during a chemical reaction?
Molecules break apart into atoms and rearrange to form different molecules.
A student in class stated that the reactants in a molecular formula are the things you end with in a chemical reaction and products are the things you being with in a chemical reaction. Is the student correct or incorrect? Explain your answer.
The student is incorrect. Reactants are the things you being with in a molecular formula and the products are the things you end with in a molecular formula or chemical reaction.
Example:
Reactants: H2 + O ----> Products: H20
Is the following a definition of a physical or chemical change?
This type of change occurs when the form or appearance of matter changes but not what is made up of.
Physical Change
Is boiling water in an open pot an example of an open system? Explain how it exchanges matter or energy with its surroundings.
Yes, it is. A boiling pot of water creates steam (matter) and heat (energy) escapes into the air.
Is a sealed bottle of soda an example of a closed or open system? Explain your answer.
A sealed bottle of soda is a closed system because it can absorb or release heat energy, but no matter enters or leaves.
Change in color, formation of a gas, formation of a solid, change in odor, change in temperature, something is burnt, or light is being produced.
A student in class stated that N2 + 3F2 -------> 2NF3 is a balanced equation. Is the student correct? Be able to explain your answer by breaking down the number of atoms on each side.
Yes, the student is correct. There are 2 Nitrogen atoms on the reactant side and product side and 6 Fluorine atoms on the reactant and product side.
Maria is making pancakes. She pours batter onto a hot pan. At first, the batter spreads out and becomes thinner. After a few minutes, bubbles form on the surface, and the batter starts turning golden brown. Finally, she adds syrup on top of the cooked pancakes. Identify all of the chemical changes in this scenario.
Bubbles forming and batter turning golden brown makings new substances form, color changes, this can not be easily reverse.
How does an open system differ from a closed system in terms of energy and matter transfer? Provide a scientific example of an Open System and Closed System.
Open systems exchange both energy and matter, while closed systems exchange only energy. Example: A living plant (open system) vs. a boiling pot with a lid (closed system).
How does a closed system differ from an open system?
A closed system exchanges only energy, not matter, while an open system exchanges both.
Liam mixes vinegar and baking soda in a cup. Bubbles form, a solid forms on the bottom the cup, and foam rises.
Is this a chemical reaction? Explain your answer with evidence of what you observed.
Yes it is a chemical reaction because new substances are formed: A gas, solid, and liquid. This is shown by the new gas- Carbon dioxide, foam (Liquid), and solid Sodium acetate.
A student in class stated that the equation follows the Law of Conservation of Mass. Is the student correct or incorrect?
2H2 + O2 -----> 3H2O
The student is incorrect. This equation is not balanced there are is only one Oxygen atom on the product side.
Lina is making lemonade. She squeezes lemons into a pitcher, then stirs in sugar and water. She adds ice cubes to chill it. After a while, she accidentally leaves some lemonade in the sun, and it starts to smell sour and taste strange.
Identify the Physical AND Chemical changes that occurred in this scenario.
Physical changes: Squeezing lemons → juice separates, but still lemons. Stirring in sugar and water → dissolving sugar, no new substance. Adding ice → melting ice changes state, still water.
Chemical change: Lemonade left in the sun → bacteria or chemical breakdown causes sour smell/taste, creating new substances.
Maria leaves a cup of hot tea on the kitchen counter. After a few minutes, steam rises from the cup, and the tea gradually cools down. Later, she notices that the tea level has gone down slightly.
Explain why Maria’s cup of tea is an example of an open system. In your answer, describe what forms of matter and energy are exchanged between the tea and its surroundings.
The cup of tea is an open system because it exchanges both matter and energy with its surroundings. Heat energy leaves the tea as it cools, and water vapor (matter) escapes into the air as steam.
A student places 200 grams of ice in a perfectly sealed, insulated container. The ice melts completely into water after some time, but no water or vapor escapes the container.
Using the Law of Conservation of Mass, calculate the total mass of the water after the ice has melted. Explain why this is an example of a closed system.
The total mass of the water is 200 grams, the same as the original ice. This is a closed system because energy (heat) may have entered to melt the ice, but no matter left or entered the container.
A student drops a piece of magnesium ribbon into hydrochloric acid. The reaction produces bubbles and the magnesium slowly disappears.
Identify the reactants and products of this chemical reaction.
Reactants: magnesium (Mg) and hydrochloric acid (HCl)
Products: hydrogen gas (H₂) and magnesium chloride (MgCl₂)
A student in class stated that the following chemical equation is balanced and follows the Law of Conservation of Mass. Is the student correct or incorrect? Why?
4Al + 3O2 ----> 2Al2O3
Yes, the student is correct. This equation is balanced and everything you start with in this reaction you finish with. 2x2 Al= 4 Aluminum Atoms and 2x3 Oxygens = 6 Oxygen Atoms.
John is baking chocolate chip cookies. He mixes flour, sugar, butter, and eggs into a dough. He then scoops the dough onto a tray. In the oven, the dough spreads out and softens. After a few minutes, the cookies turn golden brown, rise, and release a sweet aroma. Once cooled, he sprinkles powdered sugar on top. Identify the changes that would be consider both Physical and Chemical at the same time.
Both physical and chemical: Heating the dough in the oven → dough changes shape and texture (physical) while chemical reactions produce new substances (chemical).
A student places a small piece of solid dry ice (solid carbon dioxide) on a tray and leaves it on the lab table. At the start, the dry ice has a mass of 50 grams. After 10 minutes, the student measures the remaining solid and finds only 30 grams left.
Using the Law of Conservation of Mass, calculate how much carbon dioxide gas escaped into the air. Explain why this setup is an example of an open system, even though the total mass is conserved.
50 g – 30 g = 20 g of carbon dioxide gas escaped. This is an open system because matter (CO₂ gas) left the system and entered the surroundings, but the total mass of the system and surroundings stays constant
A scientist seals 100 g of water in a container and heats it until some of the liquid becomes vapor, but the container remains sealed.
Explain how the Law of Conservation of Mass applies in this closed system AND describe what happens to the total mass inside the container as the state of matter changes.
The total mass stays the same at 100 g because no matter leaves or enters the closed container. The water changes from liquid to vapor, but all the matter remains inside.
A student observes iron left outside in moist air. Over several weeks, the iron forms rust, and its mass increases.
Explain why the mass of the iron sample increases and how this demonstrates the Law of Conservation of Mass in a chemical reaction.
The mass increases because oxygen from the air reacts with the iron to form iron oxide (rust). The law of conservation of mass is shown because the total mass of iron plus oxygen equals the mass of rust
The following equation below is unbalanced and does not follow the Law of Conservation of Mass. With your team make the equation balanced.
Al + Fe₂O₃ → Fe + Al₂O₃
The following below is the equation balanced. In order to make this equation balanced you must ensure that Fe-Iron has two atoms, Al- Aluminum must have two atoms atoms, and O- Oxygen must have three atoms.
2Al + Fe₂O₃ → 2Fe + Al₂O₃
A student is performing an experiment in the lab. She does the following: She takes a piece of magnesium ribbon and cuts it into small strips. She places one strip of magnesium in a test tube and heats it with a Bunsen burner. The magnesium starts to glow brightly, producing a white powder. She dissolves some table salt in water to make a salt solution. Identify what is a physical and what is a chemical change.
1. Physical Change.
2. Chemical Change
3. Chemical Change
4. Physical Change