Mixtures & Solutions
Name one way mixtures and solutions are different.
Mixtures can be separated easily; solutions are more difficult to separate.
You have a mixture of sand and water. Which tool or process could you use to separate them?
What is a paper filter?
The part of the experiment that you change on purpose.
What is the independent variable?
The standard unit for measuring force.
What is a newton?
This property describes how well something can bend without breaking.
What is flexibility?
A student has a mixture of iron filings and sand. Which property can be used to separate them?
Magnetism — the iron is magnetic, but the sand is not
A student mixes salt and sand together. They try to use a magnet to separate them. Why won’t this work, and what should they do instead?
It won’t work because neither salt nor sand is magnetic. Instead, they should add water to dissolve the salt, then filter out the sand, and evaporate the water to get the salt back.
The part of the experiment that you measure.
What is the dependent variable?
A soccer ball is rolling on grass and another is rolling on a smooth gym floor. Which ball will slow down faster and why?
The ball on the grass will slow down faster because friction is greater on the rough surface. The ball on the smooth floor experiences less friction.
This tool is used to measure mass.
What is a triple-beam balance?
Give me an example of a Solution and explain why.
Any answer like, Powder mix and water, lemonade, etc.
Why?? Because one of the substance dissolves and cannot be separated.
A student wants to separate a mixture of rice and small beans. Which tool could help, and how would they use it?
a sieve — the sieve allows smaller grains (rice) to pass through while keeping the larger beans out.
Why is it important to repeat trials in an experiment?
To make results more reliable.
When equal forces act on an object in opposite directions, the forces are said to be ____.
What are balanced forces?
Two metal objects are the same size. One is aluminum and one is iron. If you use a magnet, how could you tell them apart?
The iron object will be attracted to the magnet (magnetism)
A student mixes sand and water in one cup and sugar and water in another. How are the two mixtures alike, and how are they different?
Both are mixtures, but in sand and water the parts can still be seen separately, while in sugar and water the sugar dissolves and the mixture looks the same throughout.
Why can’t you just pour a mixture of salt and sand into a sieve to separate them? What could you do instead?
Because both salt and sand pass through the holes in a sieve. Instead, dissolve the salt in water and then filter out the sand.
A student is testing whether playing classical music, rock music, or no music affects how fast bean plants grow. What would be the control group, and why is it important in this experiment?
The control group is the plants with no music. It is important because it shows the normal growth of plants for comparison.
A student pushes a stationary box with a force of 10 N, and a friend pushes the same box from the opposite side with a force of 6 N. What will happen to the box, and why?
The box will move toward the side with less force because the forces are unbalanced, and the stronger force causes motion.
A student is testing different materials to see which would make the best wires. Which physical property should they focus on?
Conductivity (ability to carry electricity)
Why is it usually easier to separate mixtures than solutions? Give an example of each.
Mixtures (like trail mix) are easy to separate because the parts stay separate. Solutions (like saltwater) are harder to separate because the solute dissolves and you need a process like evaporation to separate it.
A mixture contains salt, sand, and iron filings. Describe the steps and tools you could use to separate all three substances.
Use a magnet to remove the iron filings.
Add water to dissolve the salt.
Filter the sand out.
Evaporate the water to recover the salt.
A student wants to know if different amounts of fertilizer affect the number of tomatoes a plant produces.
What is the independent variable in this experiment?
What is the dependent variable in this experiment?
The independent variable is the amount of fertilizer.
The dependent variable is the number of tomatoes produced.
A soccer ball is sitting on the grass. If you kick it, it rolls. If the Earth’s gravity pulls on it, what type of force is each, and why does the ball move only when kicked?
Think about the forces!!!
Kicking is a contact force that moves the ball. Gravity is a distant force pulling downward, but it doesn’t make the ball roll horizontally on the grass.
Imagine you are asked to design a boat. Which two physical properties of materials would you need to think about the most, and why?
Density (so it can float) and strength/flexibility (so it can hold weight without breaking)