1. Introduction to Science
and
Density

2. 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

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

4. 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

5. 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

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

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

8. 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

9. 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

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

11. 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

12. 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

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

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

15. 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

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

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

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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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.

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

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

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

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

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

31. 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

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

33. 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?

34. 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

35. 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

36. 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

37. 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

38. 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

39. 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

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

41. 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.

42. 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

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

44. 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

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

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

47. 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