Physical Science - Pleasant Hill Elementary School

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Transcript Physical Science - Pleasant Hill Elementary School

Physical Science

Ch. 1 Part II

Physical Science Methods

How Familiar Are You with Units of Measurement?

 10 km is about how far in miles?

 A person who has a mass of 75 kg weighs about how much in pounds.

 About how much is a quart, and how many quarts are in a 2 liter bottle?



10 km = 6.2 miles



75 kg = 165 pounds



2 liters = 2.12 quarts

• If a long-jumper goes 7.255 m, is that good or bad?

• The speed limit says 104 km/hr. How fast is that?

• The boy weighed 78 kg. What weight class will he wrestle?

Standards

 A standard is an exact quantity used for comparison.

There are 2 commonly used systems of measurement. The

SI system

(worldwide) and

English

units (primarily in the U.S.).

 How many cubits from one side of the room to the other?

 Why do you think the U.S. does not use the SI system as much as the rest of the world?



What are some SI units which we see commonly used in the U.S.?

SI System of Measurement

 The SI system is a base ten system of measurement. All units are either multiples of 10, or decimals. Prefixes added to root words will tell you what multiple a measurement is.

For example........

 Centi- = 1/100 or .01 1 meter = 100 cm  Milli- = 1/1,000 or .001 1 meter = 1,000 mm  Kilo- = 1,000X 1,000 meters = 1 km

Time • Time is the interval between two events, and is the only measurement which uses the same units (seconds) for both SI and English measurements.

Length

 Length is a measure of the

distance

between 2 points.

 The SI unit for length is the meter (m).

• The lead in a mechanical pencil is usually measured in millimeters (mm), referring to it’s width.

Mass

 Mass is a measure of the amount of matter in an object. The SI unit for mass is the kilogram (kg).

Mass is measured using a balance (not a scale.).

• The formula for mass is Mass = Density x Volume We'll use this formula later on.

Also, 1 kg = 2.2 pounds

 A wood dowel, metal rod, and a candle all have different masses, even if they're the same size.

Is mass the same as weight?

Explain.

Volume

 Volume is the amount of space occupied by an object (how big it is).

 For a regularly shaped object (square or rectangular) volume is measured in cm 3 .

The formula is length x width x height.

• What is the volume of the object shown below?

• If you have an object that is not a perfect square or rectangle, how do you think you could find it's volume?

• The best way to find the volume of an irregularly shaped object is through water displacement.



Density

Density is the amount of mass an object or material has, based on it's volume.

For example, if I have 2 objects the exact same size, the one with more matter in it is denser.

Like a bowling ball and a styrofoam ball.

• Some examples of objects or materials where density is important: -a snowball -liquid mercury -humans floating and/or sinking -a lead sinker -warm and cold air

The Dead Sea

 The formula for density is mass divided by volume.

If mass is measured in grams and volume is measured in cm 3 , the mass/density would result in the label being g/ cm 3 .

Water for example has a density of 1 g/ cm 3 .

Derived Units

 Units which are a combination of other units are called derived units.

 Ex.: cm 3 for volume, mi/hr for speed

Temperature

• Temperature is a measure of the average kinetic energy of the particles in a sample of matter.

As you heat an object up, the particles move faster (higher kinetic energy), and the temperature increases.

• The SI unit for temperature is the Kelvin.

Although the celcius and fahrenheit scales are more commonly used.

Absolute Zero

• As the temperature of a material decreases, particle movement slows. If the temperature decreases to a point where particle movement stops completely, this is called absolute zero. (0 Kelvin) • Absolute zero is theoretical, in that it has never been achieved.

Temperature Conversions

• F = (C x 1.8) + 32 • C = (F - 32) x .55 • K = C + 273 • Ex.: If the temperature at the lake is 95 degree Fahrenheit, what is it in degrees Celsius.

(95 – 32) x .55 = 34.65 degrees Celsius

Practice Problems

1. Convert 14 degrees Fahrenheit to Celsius and to Kelvins.

A rock dropped into a beaker of water causes the water level to rise from 415 mL to 675 mL. What is the volume of the rock?

3. If the rock in problem #2 has a mass of 520 g, what is it’s density?

1. Convert room temperature (72 F) to: A. Celcius B. Kelvin 2. A brick has a height of 8 cm, width of 12 cm, and length of 20 cm. What is it’s volume?

3. If the brick in problem #2 has a mass of 3840 g, what is it’s density?

4. Will the brick float or sink in water? Explain why.

5. A beaker has 235 mL of water in it. When a flashlight battery is dropped in, the water level rises to 485 mL. What is the volume of the battery?

6. If the battery in problem #5 has a density 1.5 g/cm3, what is the mass of the battery?

1. Convert 450 cm to: A) Km B) mm 2. If the melting point of lead is 327 degrees Celsius, what is it in: A) degrees Fahrenheit B) Kelvins 3. An unknown metal has a volume of 5 cm 3 and a mass of 13.5 g. Using the table on pg. 19, identify this metal.

Graphing

A graph is a visual display of information or data.

Graphs often show patterns or relationships in the data, and may be used to predict future results.

Types of Graphs

 There are 3 main types of graphs: 1. Line graph - shows trends or patterns over time, usually with larger numbers 2. Bar graph - compares smaller values which are usually counted 3. Circle (pie) graph - shows 1 fixed quantity broken down into parts (usually percentages)

Line Graphs

• Line graphs use an X axis (horizontal) and a Y axis (vertical) to plot data points, which are then connected with either a straight or curving line.

• The data measured on the X axis is the independent variable, and the Y axis shows the dependent variable.

The graph below shows how long students had to wait while registering for school this past month.

• What does the graph show you?

• Hypothesize as to why Monday and Friday had the longest wait times.

Bar Graph

• A bar graph is very similar to a line graph, just with smaller numbers. • Also, a bar graph shows information, but may or may not show any patterns or trends.