MATTER AND MEASUREMENT

How is a controlled experiment designed?

◦A controlled experiment should have a control, a standard for comparison.

◦Controlled experiments only change one variable at a time. The one variable that changes in a controlled experiment is called an manipulated variable.

◦The thing that is affected by changing the manipulated variable is called the responding variable.

◦All of the things that stay the same in an experiment are called constants.

Read the scenario below:

Students put the same type of bacteria in 15 petri dishes. Antibiotic A was applied to 5 dishes, Antibiotic B was applied to 5 dishes, and antibiotic C was applied to the last 5 dishes. At the end of two weeks, the number of bacteria cultures were counted.

1.What were the constants?

2.What was the manipulated variable?

3.What was the responding variable?

4.Was there a control?

Which pizza has the most grease?◦Lucy and Amy buy three slices of cheese pizza: one from Dominoes, one from Pizza Hut and one from Jules. The hold each slice over a paper towel for 60 seconds and let the grease drip down onto a napkin. The observe to see which napkin has the most grease. Then they eat the pizza!

How does theory differ from a law?

Theory Law

What are the base units used in chemistry?◦Meter is used to measure length◦Kilogram is used to measure mass ◦Kelvin is used to measure temperature◦Second is used to measure time

What are the metric units of length?Kilo Hecto Deka Meter

LiterGram

Deci Centi Milli

1000 100 10 1 .1 .01 .001

Kids Have Dropped Over Dead Converting Metrics

What are the units for volume?

◦1 Liter (L) = 1000mL

◦1000 mL = 1 Liter (L)

◦1 cm3 = 1 mL

◦Volume of solids = Length X Width X Height

◦Volume of liquids = Use a graduated cylinder

◦Volume of gas /Volume of irregular solids = Use displacement of water

What are the units for mass?

◦1 Gram (g) = 1000 mg

◦1 kg = 1000 grams

Mass of solids = use electronic scale

Mass of Liquids= measure container first, then zero and add liquid

What are the units for temperature?◦C = K -273

◦K = C + 273

◦F =9/5 C + 32

◦C=5/9 (F - 32)

What is a conversion factor?

◦A ratio of equivalent measurements used to solve problems

◦1 meter = 100 cm

1 meter = 1 meter

What is dimensional analysis?

◦A way to analyze and solve problems using the units or dimensions of the measurements.

◦You need conversion factors!

Sample Problems:

◦How many seconds in a 24 hour day:

◦How many miles in 24 kilometers? (1 mile= 1.6 Km)

What are the two kinds of observations?◦Qualitative Observations describe an object’s characteristics, properties or attributes. Examples would include: color, texture or odor.

◦Quantitative Observations involve a quantity or an amount. Examples would include mass , volume or temperature.

Why are measurements expressed in scientific notation?◦Scientific notation makes large numbers easier to work with.

Sample Problems:

◦ 345.89 =

◦.00034 =

◦23.004 =

How do you evaluate accuracy and precision?Accuracy Precision

• Compare the measured value to the correct value

• Arrows hit the bullseye

• Compare the values of two or more repeated measurements

• Arrows all hit the same point

Sample Problem:

How is percent error calculated?

Experimental Value - Accepted Value X 100%

Accepted Value

How is density determined?

◦Units g/mL or g/cm3

Sample Problems:

The mass of a marble is 5.6 grams. The volume is determined using displacement of water and is found to be 4.8 mL. What is the density of the marble?

What are some examples of physical properties?◦Color◦Melting Point◦Boiling Point

What are the three states of matter and how do they compareSolid Liquid Gas

• Has a definite shape and volume

• Particles are tightly packed

• incompressible

• Takes the shape of container

• Particles are close together but not rigid or orderly

• Has a definite volume

• Not easily compressed

• Fills the container• Takes the shape of

container• Particles are far

apart• Easily compressed

What are some examples of physical and chemical changes?Physical Change Chemical Change

• Tearing• Folding• Evaporation/Freezing• Dissolving

• Flammability• Rusting

What are some signs that a chemical change has occurred?◦Color Change◦Precipitate (solid)◦Energy Transfer (heat)◦Bubbles

What are the two kinds of mixtures?Homogeneous Heterogeneous

• Appears the same throughout• Includes solutions• Can be liquids, solids and gases

• Does not appear the same throughout

How can mixtures be separated?◦ Filtering-separates solids from liquids

◦Density Method- separates solids from solids or liquids

◦Distillation- separates liquids from liquids

How do elements, compounds and mixtures compare?◦ Elements- one kind of atom

◦ Compounds- one or more atoms

◦Mixtures- two or more substances