d. a possible answer to a scientific question.

A hypothesis is a. a way to share ideas with other scientists. b. a summary of what was learned. c. the observations made during an experiment. d. a possible answer to a scientific question.

The observations and measurements made in an experiment are called a. hypotheses. b. data. c. conclusions. d. opinions.

Which of the following is a hypothesis? a. What causes ice to melt? b. Physics is the best branch of physical science. c. The results show that aluminum foil reduces friction. d. Salt water boils faster than distilled water.

Accurate measurements a. are always reproducible. b. are close to the actual values. c. result from inconsistent use of equipment. d. result from damaged instruments.

If the actual mass of a rock is 35 g, which data set below is most accurate? a. 30 g, 29 g, 29.5 g b. 37 g, 40 g, 42 g c. 38 g, 38 g, 38 g d. 34 g, 35 g, 36 g

The reproducibility of data refers to a. how close a measurement is to the true or actual value. b. the accuracy of the instruments. c. how close a group of measurements are to each other. d. the number of times an experiment is repeated.

The actual length of a rectangular room is 6.50 meters. A student measures the length of the room three times and gets measurements of 7.49, 7.50, and 7.48 meters. The student s measurements can be described as a. both accurate and reproducible. b. accurate but not reproducible. c. reproducible but not accurate. d. neither accurate nor reproducible.

The manipulated variable in an experiment is the variable that a. is not measurable. b. changes in response to changes in other variables. c. is kept constant. d. is purposely changed.

A student is testing whether changing the volume of a substance will change its density. Which of the following is the responding variable? a. the density of the substance b. the mass of the substance c. the volume of the substance d. the weight of the substance

A student designs a controlled experiment to test how the shape of an object affects how fast it falls when dropped. Which of the following is not a controlled parameter in the student s experiment? a. the shape of the object b. the mass of the object c. the height from which the object is dropped d. the initial velocity of the object

Archimedes Principle 9/21 or 9/22 How can you tell if something is made from pure gold?

Archimedes Principle Archimedes and the Crown

Archimedes was a great scientist who lived more than 2000 years ago in a Greek city called Syracuse. He was very clever at inventing and figuring out how things work, so King Hiero needed his help many times.

Once King Hiero gave a goldsmith lots of gold to make a big beautiful crown. The goldsmith made it shaped like a beautiful ring of gold leaves. But King Heiro told Archimedes that he was worried. He did not trust the goldsmith. The goldsmith could have kept some of the gold for himself and mixed something else with the rest of the gold to trick him.

King Heiro had a beautiful new gold crown, but was it really all gold? He wondered and wondered. He could find out by having the crown melted to see what it was made of, but then he would not have a crown. He needed someone clever like Archimedes to help him.

Archimedes wanted to help King Heiro. The King should have a real gold crown! If the goldsmith was a thief, he should go to jail! But how could he find out if it was all gold without ruining the crown?

Archimedes was so busy thinking about the puzzle that he didn't pay very much attention to what he was doing when he was filling up his bath tub that night. When he got in to take a bath, water spilled all over the floor.

The thing that made Archimedes such a great scientist was that he always wondered about things. He thought, I wonder why the water spilled out when I got in? Obviously there wasn't enough room in the tub for him and all that water.

So how much water had to spill out? Archimedes took his bath toys and did some experiments. The bigger something was, the more water spilled. So even if a bath toy had a very unusual shape, he could tell how big it was by how much water spilled out.

Archimedes noticed that some things that were big were very light and floated, but some things that were small were very heavy and sank. Everything had different densities. Things like rocks that had more density sank. Things like rubber ducky and Allie Alligator had less density and floated. Rubber ducky was lighter than rocks.

Suddenly, Archimedes knew how to find out if the crown was real gold. He was so excited he shouted "Eureka!", which is Greek for "I found it!" He got up and went running through the streets of Syracuse shouting "Eureka! Eureka! Eureka!" Archimedes was so excited that when he got out of the bath he forgot he wasn't wearing any clothes!

Archimedes ran to King Heiro and announced that he could solve the crown puzzle. King Heiro said "That's great, but first put on some clothes!"

After getting dressed, Archimedes explained to the King how to decide if the crown was pure gold without ruining it. First he put the crown in a bowl of water and drew a line where to top of the water was. Then he took out the crown and put in gold until the water reached the line again.

Now Archimedes knew he had a pile of gold that was the same size as the crown. If the crown was pure gold, then it must be the right density for gold. So, if the crown was gold, and had the right density for gold, it must be exactly as heavy as the pile of gold. It would have to balance with the pile of gold. They put the pile of gold and the crown on different ends of a balance to find out.

Now they knew the truth about the crown. King Heiro was happy. Archimedes was happy. EVERYBODY WAS HAPPY!

Well, almost everybody was happy!

Vocabulary Mass The amount of matter in an object Weight a measurement of a gravitational force between two objects. Density Mass per unit volume Physical property

Density Notes Density = Mass/Volume g/cm 3 or g/ml Volume = length x width x height Volume through water displacement

Density Notes

Density Notes BF > Gravity Positive Buoyancy BF = Gravity Neutral Buoyancy BF < Gravity Negative Buoyancy The object is less dense than the liquid. The object is the same density as the liquid. The object is more dense than the liquid.

Does the density of a substance ever change? A block has a mass of 10 grams and a volume of 5 ml. What is it s density? That same block is cut exactly in half. What is it s density now? 10 g/5 ml = 2 g/ml 5 g/2.5 ml = 2 g/ml

Substance g/cm 3 water 1.00 aluminum 2.70 zinc 7.13 iron 7.87 copper 8.96 silver 10.49 lead 11.36 mercury 13.55 gold 19.32

Formative Assessment Today You will be given the equation: D = m/v 1 Calculation Problem where you are given the mass and volume of an object. 1 Calculation Problem where you are given the mass and dimensions of an object. 1 Calculation Problem where you are given the mass and you need to calculate how much water has been displaced and then find the density of the object.

Density Practice Problems 1) g/cm 3 or g/ml 2) 30 g/cm 3 3) 2 g/cm 3 4) 3 g/cm 3 5) 4 g/cm 3 6) 4 g/ml 7) 2.5 g/cm 3 8) 2 g/cm 3 ; Sink 9) 17.5 grams 10) 200 cm 3 11) 204 grams 12) 5 cm 3 ; Same Density

Density Notes The buoyant force is equal to the weight of the volume of fluid displaced by the object. A child gets into a full bath tub. The water that spills out weighs 5 N. The buoyant force acting on the child is 5 N.

Density Competition Rules You may choose your group Prove to me that you can work with the people you choose 3-4 people in a group INCLUDE EVERYONE!!! Your team gets: 1 Triple Beam Balance 1 Small Graduated Cylinder 1 Large Graduated Cylinder Access to the Digital Balances No more than two objects at one time