Warm-up

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# Warm-up - PowerPoint PPT Presentation

Warm-up. What instrument would you use to measure temperature? Which of the following is a unit of volume? a. gram b. atmosphere c. meter d. liter What property of matter can you measure using a graduated cylinder? . Thermometer. Volume. Classifying Matter.

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Presentation Transcript
Warm-up
• What instrument would you use to measure temperature?
• Which of the following is a unit of volume?

a. gram b. atmosphere c. meter d. liter

• What property of matter can you measure using a graduated cylinder?

Thermometer

Volume

Classifying Matter
• Classify pure substances as elements and compounds.
• Describe the characteristics of an element and the symbols used to identify elements.
• Distinguish pure substances from mixtures.
• Classify mixtures as heterogeneous or homogeneous.
• Classify mixtures as solutions, suspensions, or colloids.
Matter?
• What is matter?
• Anything that has mass and takes up space
• Why do we need to classify matter?
• Not all matter is the same.
• Different types of matter must be treated differently.
• Example
• Not all clothes are made of the same fabric.
• Clothes require different washing techniques.
Matter Classification

Matter

Pure Substances

Mixtures

Elements

Compounds

Homogeneous

Heterogeneous

Pure Substances
• Made up of all the same thing or one type of matter.
• Pure substances have the same properties regardless of sample.
• Either compounds or elements
Elements
• Substances that cannot be broken down into simpler substances.
• Think of atoms.
• Contain only one type of atom.
• It has a fixed composition
• Ingredients can’t change.
• Identified by symbol
• Examples of elements:
• Aluminum (Al), Gold (Au), Carbon (C) - solids
• Bromine (Br2), Mercury (Hg) - liquids
• Oxygen (O2), Nitrogen (N2) - gases
Compounds
• Substances that are made up of two or more simpler substances that can be broken down.
• They are combined in chemically defined ratios.
• H2O – Water, C6H12O6 – Glucose (Sugar).
• The elements have different properties when alone.
• Hydrogen and Oxygen are flammable as elements.
• But water is not flammable.
• Identified by formula
Mixtures
• The make-up of mixtures are not fixed.
• Properties vary by mixture contents.
• They retain some of the properties of the individual substances.
• Sand is an example of mixture.
• One could find sand from many different beaches but all could have a very different make up.
• Mixtures can be classified by how well the parts of the mixture are distributed throughout it.
Heterogeneous Mixtures
• The Greek words hetero and genus meaning “different” and “kind.”
• Two or more types of atoms, physically combined in no definite ratio.
• Different throughout.
Homogeneous Mixtures
• Two or more substances, physically combined in no definite ratio.
• Same throughout.
• Must be a SOLUTION
• A solute dissolved in a solvent.
Measuring the volume of liquids
• Liquids have volume. We measure that volume with a graduated cylinder.
• Notice the meniscus in the graduated cylinder.
• Always measure at the bottom of the meniscus!
• A liquid in any container has a meniscus.
• Liters (L) and mL (milliliters) are most often used to express the volume of liquids.
Solid Volume
• If each side in the cube below is 2m, what is the volume of the cube?

__________

• The volume in a solid is always expressed in cubic units.
• Cubic means having “three dimensions.”
• Cubic meters(m3) or cubic centimeters(cm3) are most often used to express the volume of a solid.
• The 3 in m3 signifies that three quantities were used to get the final result. (That is a derived quantity!)
The Volume of Solids, Liquids, and Gases
• 1 mL = 1 cm3 REMEMBER THAT!
• That is why you can compare the volume in liquids to solids.
• How do you measure the volume of a gas?
• You can’t see, so how do you measure it?

ex: balloon

_________________________

Measuring Weight and Mass
• The SI unit for mass is kilogram (kg).
• Sometimes we will use milligrams or grams. (mg or g)
• The SI unit for weight (or gravitational force) is NEWTONS.
• A Newton is approximately equal to the weight of a 100 gram mass on earth.
The major differences between
• WEIGHT
• A measure of the gravitational force on an object.
• Varies depending on where the object is in relation to the earth. Example: ____________
• Measured with a spring scale.
• Expressed in Newtons.
• MASS
• A measure of the amount of matter in object.
• Always constant, no matter the location.
• Measured with a balance.
• Expressed in kilograms, grams, and milligrams.
Describing Matter
• Knowing the characteristics or properties of an object can help you identify the object.
• There are:
• Physical Properties
• Chemical Properties
Physical Properties
• Things that describe the object are physical properties.
• Physical properties can also be observed or measured without changing the identity of the matter.
• Examples of physical properties include: color, odor, size, state, density, solubility, melting point, etc…
Spotlight on Density
• Density is a very helpful physical property.
• Density = mass per unit of volume or Density = mass/volume
• Density is an excellent help in identifying substances because each substance has its own density.
Chemical Properties
• Chemical properties describe a substance based on its ability to change into a new substance with different properties.
• Ex: wood burns to form ash and smoke
• Chemical properties cannot be observed with your senses.
• Chemical properties aren’t as easy to observe as physical properties.
• Examples of chemical properties: flammability and reactivity
Characteristic Properties
• The properties that are most useful in identifying a substance are its characteristic properties.
• Remember the difference between physical and chemical properties.
• Physical properties can be observed! (with your eyes!) IDENTITY OF SUBSTANCE DOES NOT CHANGE!
• You can observe chemical properties only in situations in which the identity of the substance could change.
Physical Changes
• A physical change is a change that affects one or more physical properties of a substance.
• Physical changes do not form new substances! EX: ice melting or sugar dissolving
• Physical changes are easy to undo.
Chemical Changes
• A chemical change occurs when one or more substances are changed into entirely new substances with different properties.
• You can observe chemical properties only when a chemical change might occur!
• Examples of chem. changes:

baking a cake

rusting

Clues to chemical changes
• Color change
• Fizzing or bubbling (gas production)
• Heat
• Production of light, sound, or odor.
• Chemical changes are not usually reversible!