Scientific Models
What is the main purpose of a scientific model?
A) To decorate a science lab
B) To represent objects, systems, or events
C) To replace real objects
D) To confuse scientists
B) To represent objects, systems, or events
What does the Particle Model of Matter state about the composition of all matter?
A) All matter is made of large, visible particles
B) All matter is made up of tiny particles
C) Only liquids and gases are made of particles
D) Only solids are made of particles
B) All matter is made up of tiny particles
What should a scientist do after analyzing the results of an experiment?
A) Start the experiment again
B) Develop a new hypothesis
C) Write a conclusion based on the data
D) Skip to the next experiment
C) Write a conclusion based on the data
TRUE OR FALSE:
The solvent is the substance that is dissolved in a solution.
False
This is false because the solvent is the substance that dissolves the solute, not the one being dissolved.
In the given problem:
What is the percent by volume of a solution made by dissolving 110 mL of ethanol in 15 mL of water?
What formula will you use?
Volume percentage:
Volume percentage = (vol of solute/vol of solution) x 100
Which of the following is an example of an object that is too small to see and is often represented by a scientific model?
A) A mountain
B) An atom
C) A car
D) A tree
B) An atom
What happens to the motion of particles when the temperature increases?
A) Particles move slower
B) Particles move faster
C) Particles stop moving
D) Particles disappear
B) Particles move faster
IDENTIFICATION:
A group of students wants to know if the type of liquid affects how quickly ice cubes melt. They place identical ice cubes into cups containing water, milk, and orange juice, and then measure the time it takes for each ice cube to melt completely. All the liquids start at the same temperature.
What is the dependent variable in this experiment?
The time it takes for the ice cubes to melt
How does increasing the temperature generally affect the solubility of most solids in liquids?
A) Solubility decreases
B) Solubility remains the same
C) Solubility increases
D) Solubility becomes unpredictable
C) Solubility increases
Scenario: What is the percent by mass/volume percent of a 150 mL saline solution that is prepared by dissolving 25 grams of salt in water?
What is the given in this scenario?
Given:
Solute = 25g of sugar
Solution = 150 mL
What type of scientific model involves equations and is often used to predict events like weather?
A) Physical model
B) Conceptual model
C) Mathematical or computer model
D) Historical model
C) Mathematical or computer model
How are particles arranged in a solid?
A) They are far apart and move freely
B) They are close together and vibrate in place
C) They are randomly spaced and move rapidly
D) They are scattered and move in all directions
B) They are close together and vibrate in place
IDENTIFICATION:
A scientist is studying how the angle of a ramp affects the speed of a toy car. The scientist tests the car on ramps with different angles (10°, 20°, 30°) and measures the speed of the car as it travels down each ramp. The car and the ramp surface are kept the same in each trial.
What is the independent variable in this experiment?
The angle of the ramp
A student is preparing a cup of hot chocolate by mixing cocoa powder and milk. The student stirs two tablespoons of cocoa powder into a cup of warm milk until the powder is fully dissolved.
Question:
In this hot chocolate mixture, what is the solute and the solvent?
Solute: The cocoa powder (because it is the substance that dissolves in the milk)
Solvent: The milk (because it is the liquid that dissolves the cocoa powder)
Scenario: What is the percent by volume of a solute if 28 mL of it is dissolved in a solvent of 70 mL?
Provide your solution (3rd step) to the scenario?
Solution:
Volume percentage = (28 mL / 98 mL) × 100
Which of the following is a limitation of using scientific models?
A) Models can save time, money, and lives
B) Models can perfectly replicate real-world objects
C) Models lose some accuracy to simplify communication
D) Models can include all details of the objects they represent
C) Models lose some accuracy to simplify communication
TRUE OR FALSE:
Sublimation is the process where a solid changes into a liquid before becoming a vapor.
FALSE
The statement is false because sublimation is a phase change where a solid turns directly into a vapor (gas) without passing through the liquid phase. The correct process described in the statement—where a solid turns into a liquid before becoming a vapor—is called melting (solid to liquid) followed by evaporation (liquid to vapor).
IDENTIFICATION:
An experiment is conducted to see if the type of fertilizer used affects the number of tomatoes produced by a tomato plant. Three different fertilizers are used on identical tomato plants, and the number of tomatoes produced by each plant is counted after one month. All plants are kept in the same type of soil, given the same amount of water, and exposed to the same amount of sunlight.
What is the controlled variable in this experiment?
The type of soil, amount of water, and exposure to sunlight
TRUE OR FALSE:
Increasing the temperature of a solvent typically decreases the solubility of most solids.
FALSE
This is false because, generally, increasing the temperature increases the solubility of most solids in liquids. Higher temperatures provide more energy for solute particles to dissolve.
Solve the following:
What is the percent by mass of 16.0 g of iron (II) sulfate dissolved in 85.0 g of water?
Show the given, asked, formula, solution, and final answer.
Given:
Solute: 16.0 g iron (II) sulfate
Solution: 101 g (16g + 85g)
Asked: Percent by mass
Formula:
Mass percentage = (Mass of Solute / Mass of Solution) × 100
Solution:
Mass percentage = (16 g / 101 g) × 100
Final answer: 15.84 %
Which of the following is an example of a conceptual model?
A) A 3D model of the solar system
B) A mathematical equation predicting an earthquake
C) A diagram explaining the process of photosynthesis
D) A computer simulation of a weather system
C) A diagram explaining the process of photosynthesis
IDENTIFICATION:
You notice droplets of water forming on the outside of a cold glass of lemonade on a warm day.
What type of phase change is occurring when droplets of water form on the outside of the cold glass of lemonade?
Condensation
Condensation occurs when a gas changes into a liquid. In the provided scenario, droplets of water form on the outside of a cold glass of lemonade on a warm day because the warm air around the glass contains water vapor. When the warm air comes into contact with the cold surface of the glass, the temperature of the air drops, causing the water vapor to lose energy and change from a gas (vapor) into a liquid (water droplets). This process is called condensation.
Scenario: A student notices that the amount of time their cat spends playing with a new toy seems to increase when the toy makes noise compared to when it is silent. The student wonders if the noise from the toy affects how much time the cat plays with it.
Question: Formulate a hypothesis based on this observation.
Hypothesis: If the toy makes noise, then the cat will play with it for a longer period compared to when the toy is silent.
TRUE OR FALSE:
You have 200 mL of water, and at a specific temperature and pressure, the maximum solubility of sugar in this amount of water is 80 grams. You dissolve 40 grams of sugar into the 200 mL of water.
You have made a concentrated solution because you dissolved 40 grams of sugar, which is half of the maximum amount of sugar that can dissolve in 200 mL of water at this temperature and pressure.
FALSE
Since 40 grams of sugar is only half of the maximum solubility (80 grams) that can dissolve in 200 mL of water, the solution is diluted, not concentrated. A concentrated solution would have the solute amount closer to the maximum solubility.
Solve the following:
What is the percent by mass/volume of a 1,500 mL solution that is prepared by dissolving 275 grams of calcium in water?
Show the given, asked, formula, solution, and final answer.
Given:
Solute: 275 g
Solution: 1500 mL
Asked: Percent by mass/volume
Formula:
Mass/Volume percentage = (Mass of Solute / Volume of Solution) × 100
Solution:
Mass/Volume percentage = (275 g/ 1500 mL) × 100
Final answer: 18.33 %