Introduction to Science and Density

What is Science? Science is what scientists do Science is trying to explain the world around us “Science is a system of knowledge based on facts or principles” Science is a way of thinking

Branches of Science Science Biological Science Earth Science Physical Physics Chemistry Science of matter and energy

Science and Technology Pure Science - search for scientific knowledge Technology – application of science Two are interrelated Technology develops new tools for investigating nature New science leads to new applications

Scientific Theory A reasoned explanation tested by many observations and experiments Tells why things are Three things Must explain clearly and simply Must be repeatable Must be able to make predictions Theories can be changed or modified by new evidence

Scientific Law Describe what happens Quantitative – use numbers and equations to describe equations are often part of scientific law Mathematics is a universal language

Law vs. Theory Law Theory Describes how Explains why Summarizes observations Agrees with observations Usually an equation Predicts new discoveries

Observations Qualitative – describe with words Hot , red, large Quantitative – describe with numbers 100° , 10 meters, 3.46 grams Scientists prefer quantitative Easy to agree upon No personal bias

Models A representation of some object or event Physical models Models are made to better understand things Often used if real thing is too big, too small or complex. Models Come in a variety of forms: Physical models Diagrams Computer models

The Scientific Method A way of thinking about and solving problems It is a logical method You do it all the time

The Scientific Method Starts with observation- can be anything Question – what do you want to know? Gather data- what is already known Form hypothesis- a possible explanation Design experiment to test hypothesis This is the hard part

The Scientific Method Experiments generate more observations Allow us to draw conclusions about hypothesis Support the hypothesis or not If the hypothesis is not supported then the hypothesis must be modified

Experiment tests hypothesis The Scientific Method Formulate a question Collect data Observe Form hypothesis Experiment tests hypothesis Observation Draw Conclusions

Tables Organizing data into groups Putting those groups into rows and columns Gives us an easy way to compare data

Graphs Give a visual representation of data Summarizes data. Two types of variables: Independent variable the thing you have control over and is shown on the x-axis Dependent variable the thing that you don’t have control over and is shown on the y-axis

Circle Graphs Often called a pie chart divided into parts easy to compare to whole amount. Use several to show changes over time

Bar Graphs Bar Graphs- wide columns used things like weight, height , and length. Compare quantities

Line Graphs Line Graphs- compares sets of data, show change and patterns over time.

Graphs include A title Labeled axes A consistent scale. Y to the sky Axis is on the vertical And shows the Dependent variable Axis is on the Horizontal and shows The independent variable Y to the sky

Chemistry The study of matter and how it changes Matter – anything that has mass and takes up space Mass – resistance to change in motion Two types of matter- Substance- Pure Mixture- more than one substance

Pure Substance Elements and compounds Only one kind of molecule or atom Compounds have specific amounts of their elements Compounds are completely different from their elements

Mixture Different substances mixed together Can be in any proportion Keeps the same properties as the things that make it Kool-aid Mix something sweet, something wet and something red Get something sweet, wet and red

Two Types of Mixtures Heterogeneous- Homogeneous- Different from place to place Not evenly mixed Chocolate chip cookie, gravel, soil Homogeneous- The same throughout Evenly mixed Kool-aid, sea water, air

Liquid Mixtures Miscible- Immiscible- Liquids that do dissolve in each other Homogeneous Gasoline Immiscible- Liquids that don’t dissolve in each other Heterogeneous Oil and water

Kinetic Theory Kinetic means motion Three main parts of the theory All matter is made of tiny particles These particles are in constant motion and the higher the temperature, the faster they move At the same temperature, heavier particles move slower.

States of Matter Solid Particles are tightly packed Stuck to each other in a pattern Vibrate in place Can’t flow Constant volume

States of Matter Liquid Particles are tightly packed Able to slide past each other Can flow Constant volume

States of Matter Gas Particles are spread out Flying all over the place Can flow Volume of whatever container their in

Gases Fill the available space Particles moving at about 500 m/s Particles hitting things cause pressure

Volume Liter a common unit 1 mL is about 20 drops of water or 1 sugar cube

Density Found by dividing the mass by volume D = m V Units of g/mL or g/cm3 Water has a density of 1 g/mL Ratio of mass to volume If the density of substance is less than its surroundings, it floats

Density D M V Cover up the one you are looking for to find the formula for the missing piece

Density M V D A piece of wood has a mass of 12 g and a volume of 16 cm3 What is its density? Steel has a density of 7.8 g/cm3. How much would 56 cm3 of steel weigh? What would the volume of the same mass of water be?

Liquids Spread out on their own Fluids- gases and liquids both flow Viscosity- the resistance to flow The better the molecules stick to each other, the more resistance

Energy The ability change or move matter As you add energy to a liquid, the temperature goes up The molecules move faster Eventually they will move fast enough to break free and become a gas This is evaporation- the change from a liquid to gas

Phases Changes If you change rapidly enough, the gas will form below the surface an boil Condensation- Change from gas to liquid As you cool a gas the molecules slow down As gas molecules slow down they stick together

Phases Changes Molecules and atoms don’t change during a phase change the composition doesn’t change The mass doesn’t change The volume does change Only the attractions and motion change

Law of Conservation of Mass In all changes, mass cannot be created or destroyed All the mass you start with you end with It might be hard to count

Law of Conservation of Energy In all changes, energy cannot be created or destroyed All the energy you put in, you get out It might be hard to count

Properties A property is a something that describes matter An adjective Used to identify the matter Used to distinguish between different types

Chemical Properties Used to describe how substance reacts How it changes By combining with other substances Or breaking apart Reactivity how a substance combines with other substances Things like flammability, rusting, etc.

Physical Properties Can be observed or measured without changing the composition Melting point , boiling point, hardness, odor, ability to conduct electricity and heat Density – how heavy something is for its size

Properties Allow us to identify substances Allow us to separate substances Determine uses

Changes Two types- Physical Changes- no new type of matter is made All the molecules stay the same Chemical Change- a new type of matter is made Atoms rearrange to make new elements or compounds

Chemical Changes Completely new properties Products are not at all like the reactants Makes new odor, color, etc.

Physical Changes Might look a little different Keeps original properties Changing phases Making a mixture Cutting Grinding Dissolving

Dissolving Sugar Water molecules break apart and surround sugar molecules All the original molecules are still there Sugar gets so spread out that they don’t block light