What Floats and What Doesn’t Float? (Depends on Density)
New this week: Explanation of the experiment on YouTube:
https://www.youtube.com/watch?v=xKB1QNQWVBk
Have patience! Next week the videographer will not rotate the cell phone.
STOP AND THINK:
1) Would a rock the size of a marshmallow float on water?
2) Would a marshmallow float on water?
THINK AND PREDICT:
A marshmallow in one hand, a rock about the same size in the other hand.
Which is heavier?
Which will float in the water and be less dense than water?
Which will sink in water and be more dense than water?
Write your predictions in your science journal.
LOOK IT UP: Look up the word “density.”
Write the definition in your journal.
Explain why a rock is denser than a marshmallow.
THINK AND PREDICT:
Are all liquids the same density?
Would some liquids float on another liquid?
Would some liquids SINK if added to another liquid?
Are some liquids denser than other liquids? Why?
Write your predictions in your science journal.
EXPERIMENT:
Materials needed to determine sinking and floating of liquids and solids
Measuring cup
Measuring spoons
Salt
Water
Several wide bowls or cups
Dark food coloring (optional)
Liquid oil
Orange or tangerine, lime, lemon
Raw egg
UNDERSTAND: The denser an object is (rock vs. marshmallow), the more likely it is to sink through liquid!
Experiment #1: Which liquid is denser… tap water or salt water?
PREPARATION AND PROCEDURE:
Put the same amount of warm tap water in two large cups.
Put 3 Tablespoons of salt in one cup of warm water and stir until it is dissolved.
Add 2 drops of dark food coloring to the salt water and stir.
Splash a few drops of the salt water into the cup of fresh tap water.
OBSERVE AND EXPLAIN:
1) What happened to the drops of colored salt water when you added them to the fresh tap water?
2) Which is denser: salt water or fresh water?
Write your findings in your journal.
Experiment #2: Will oil float on salt water? Will salt water float on oil? Will they just mix?
PREDICT: What will happen when one is poured into the other?
Write your prediction in your journal.
PREPARATION AND PROCEDURE:
Pour 1/4 cup of water into a clear glass.
Pour 1/4 cup of oil into the same glass.
OBSERVE AND EXPLAIN: What happened?
Write your observations in your journal.
PREDICT: Would the outcome be the same if you poured the oil in first and then added the water?
Write your prediction in your journal.
PREPARATION AND PROCEDURE:
Pour 1/4 cup of oil into a clear glass.
Pour 1/4 cup of water into the same glass.
OBSERVE: What happened? Did the order in which you added the liquids make change in the outcome? Why?
Write your observation in your journal.
ANSWER THESE QUESTIONS IN YOUR JOURNAL:
1) Which floats: oil or salt water?
2) Which is denser – oil or salt water?
EXTEND: Try these experiments!
Experiment #3: Will a raw egg float or sink in tap water? Will a raw egg float or sink in salt water?
PREPARATION AND PROCEDURE:
Put one cup of water in two clear glasses or jars.
Add 3 teaspoons of salt to one of the cups of water and stir.
PREDICT: Will the egg float in one or both of the containers? Will the egg sink in one or both of the containers?
Write your predictions in your journal.
OBSERVE:
1) Drop the egg carefully into the warm tap water and observe.
2) Drop the egg carefully into the warm salt water and observe.
EXPLAIN: What do you see? Which type of water does the egg float in? Which does the egg sink in? Was the tap water denser than the egg? Was the salt water denser than the egg? Use the word dense or denser in your journal response.
Write your responses in your journal.
Experiment #4: Do solids float or sink? Which solids sink and which solids float?
PREPARATION AND PROCEDURE:
Fill a glass or jar with water.
PREDICT: Is a piece of fruit denser than water?
Write your prediction in your journal.
OBSERVE:
Put a lemon, lime or orange in the water.
EXPLAIN:
What happens? Does it sink or float?
Write your observation in your journal.
PREDICT: What will happen if you peeled the fruit and then put it in the water?
Write your prediction in your journal.
OBSERVATION:
Peel the fruit and place it in the water.
EXPLAIN:
What happens? Why?
Write your observations in your journal.
EXTEND FURTHER: Use the same preparations and procedures to experiment with warm water and oil, then in warm water and salt. Gather solids around your yard or house to use in the experiment. Be sure to predict first, observe and then log your findings in your journal! Don’t forget to use your academic vocabulary (dense, denser, density) in your writing.
Think about what you learned and answer these questions:
1) What is an object that will float in water?
2) What is an object that sinks in water?
3) Which is denser – the object that floats or the object that sinks?
4) Are all solids the same density? Yes or No
5) Which floats – oil or salt water?
6) Which is more dense – oil or salt water?
7) Which is more dense – salt water or regular water?
8) Can you think of an object that floats in salt water but not in fresh water?