8-1 Measuring Matter

Properties and Changes of Matter- Comp. Sci. 3Mrs. Bloch

Vocabulary

Weight- a measure of the force of gravity on an object

Mass- the amount of matter in an object

International System of Units- a system of units used by scientists to measure the properties of matter

Volume- The amount of space that matter occupies

Density- a measure of the mass of a material in a given volume

My Planet Diary pg. 290Field Trip - Travel to the eastern coast of Africa and you will find the

country of Djibouti. There, you can visit one of the saltiest bodies of water in the world. Lake Assal is ten times saltier than the ocean. Its crystal white beaches are made up of salt. While on your visit to Lake Assal, be sure to take a dip in the clear blue waters. Take a book or magazine with you to read. Wait, what? Take a book into a lake? It might seem strange, but bodies of water with high salt contents, like Lake Assal or the Dead Sea in the Middle East, allow you to float so well that it's nearly impossible to sink below the surface of the water.

Communicate - What water activities might be easier to do in Lake Assal’s salty water?

What activities could be more difficult?

What Units Are Used to Express Mass and Volume? Pg. 291

Weight is a measure of the force of gravity on an object. Weight varies with location in the solar system. A more massive object will exert a greater gravitational force, so the weight of an object on that more massive planet or moon will be greater. Weight is measured with a scale.

Mass is the amount of matter in an object. It does not change with location. Mass is constant. For this reason, scientists prefer to describe matter in terms of mass rather than weight.

Measuring Weight – figure 1 pg. 291Use the weight of the first scale to estimate the weight of the fish on the other scales.1.Estimate – Use the weight of the first scale to estimate the weight of the fish on the other scales. Draw in the pointers.2.Describe- How would their weight change on a small planet like Mercury? Or a large planet like Neptune? ___________________________________________________________________________________

The International System of Units or SI pg. 292To measure the properties of matter, scientists use the

International System of Units, or SI. The SI unit of mass is the kilogram (kg). If a smaller unit of mass is needed, the gram (g) is used. There are 1,000 grams in a kilogram or 0.001 kilogram in a gram.

Measuring Mass – Figure 2- pg. 292The SI system uses grams and kilograms to measure mass.

1.Calculate – In the table, convert the mass of each object from grams to kilograms.

2. Challenge- Suppose you are taking a flight to Europe. You are only allowed a 23-kg suitcase. How much is that in pounds? (Hint: 1kg = 2.2 lb)

o 50.6 lbo 46.2 lbo 10.5 lb

Volume pg. 293

Another measurable property of matter is volume, or the amount of space matter occupies. The SI unit of volume is the cubic meter (m3). Other common SI units of volume are the cubic centimeter (cm3), the liter (L), and the milliliter (mL).

There are 1,000 milliliters in a liter or 0.001 liter in a milliliter. One milliliter is the same volume as 1 cm3. The volume

of a rectangular solid is calculated according to the following formula.

Volume = Length x Width x Height

Calculating Volume – Figure 3 pg. 293What is the volume of the suitcase?

Suppose you want to knowThe volume of a rectangularObject, like one of the suitcasesShown in figure 3. First, measureThe length, width, and height(or thickness) of the suitcase. Then, multiply the measurementsTogether. Volume = Length x Width x HeightWhen you multiply the three measurements, you Must also multiply the units. cm3 = cm x cm x cmFind the volume of the suitcase. _______________________

Measuring Irregular Objects pg. 293

One way to measure the volume of an irregular object is to submerge it in liquid in a graduated cylinder.

The water level will rise by an amount that is equal to the Volume of the object in milliliters.

Assess Your Understanding pg. 293

1. Describe- Why is mass more useful than weight for measuring matter? _______________________________________________

_______________________________________________

I get it! Now I know that the SI unit for mass is ______________

the SI unit for volume is ____________

Calculating Density pg. 294Density is a measure of the mass of a material in a given volume.

Density is expressed as the number of grams in one cubic centimeter, or g/cm3. Because one milliliter is the same volume as one cm3, density can also be expressed as g/mL. You can determine the density of a sample of matter by dividing its mass by its volume.

How Is Density Determined? Pg. 294The density of water is 1 g/mL, or 1 g/cm³. Objects with greater

densities will sink. Objects with lesser densities will float. Density is a physical property of a substance. It can be used to identify an unknown substance.

The Formula to find Density is:

1. Apply Concepts- Liquids can form layers based on density. Which colored layer of liquid represents Water: 1.g/ml, Honey: 1.36 g/ml, Dish Soap: 1.03 g/ml, Corn Syrup: 1.33 g/ml, Vegetable oil: 0.91 g/ml?-Find and circle the median density.2. Calculate- What is the density of a liquid with a mass of 17.4 g and a volume of 20 mL? Where would this liquid be in the column?3. Explain why the liquid with the median density floats where it does.

Using Density- Virtual Lab- Figure 4 pg. 295

Density can be used to identify substances.

Estimate- Hypothesize which rock sample is gold. Then calculate the density of each sample. Circle the rock that is real gold.

My hypothesis is that the gold rock is o A o Bo C

A : Mass = 108 g Volume = 12 cm3 Density = _______

B: Mass = 126 g Volume = 15 cm3 Density = _______

C: Mass = 386 g Volume = 20 cm3 Density = _______

Assess Your Understanding pg. 295

2a. Identify – Maple syrup will (float / sink) in water because its density is greater than 1 g/cm3.

b. Calculate - What is the mass of a sample of a substance with a volume of 120 mL and a density of 0.75 g/mL?

___________________________________________________

c. Challenge – Liquid water and ice are the same substance, H20. How would you explain why ice floats in water?

____________________________________________________________________________________________________

I get it! Now I know density is calculated by _________________

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