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Physical Science (chemistry)
Terms in this set (108)
anything that has mass and takes up space
matter that always has exactly the same composition; same properties; fixed, uniform composition (examples--table salt, table sugar)
two classification of substances
elements and compounds
a substance that cannot be broken down into simpler substances; fixed composition because it contains only one type of atom
smallest particle of an element
Can two different elements contain the same type of atom?
At room temperature, most elements are in what form?
main gases in the air you breathe
oxygen and nitrogen
the only two elements that are liquids at room temperature
bromine and mercury
scientist that suggested that chemists use symbols to represent elements
since element symbols can be used with any language speaking chemist they are
a substance that is made from two or more simpler substances and can be broken down into those simpler substances
a compound can be broken down into one of two things...
elements or other compounds
a compound always contains two or more elements joined in a fixed
substances blended or stirred together
Properties of a mixture may vary because the composition of a mixture is or is not fixed?
Mixtures are classified on how well the differents parts (ingredients) are __________ throughout it.
two types of mixtures...
heterogeneous and homogeneous
in this mixture, the parts of the mixture are noticeably different from one another; not distributed very evenly
in this mixture, the parts or substances of this mixture are so evenly distributed that its parts are difficult to distinguish from one another; looks to be made of only one substance
Which type of mixture would salsa be?
Which type of mixture would milk be?
If it is hard to tell if a mixture is heterogeneous or homogeneous, you must observe it properties or the ______________________.
size of its particles
three classification of a mixture
solution, suspension, or colloid
when a substance dissolve and form a homogeneous mixture, the mixture is a .....
examples of a solution( their particles are too small to separate simply by filtering)
tap water, lemonade
A heterogeneous mixture that will separate over time is what type of mixture?
example of a suspension(its particles can be separated by filtering)
sand and water/ oil and water/ salad dressing
a mixture that contains some particles that are intermediate in size between the small particles in a solution and the large particles in a suspension
example of a colloid(particles do not separate into layers and do not separate when filtered)
Why does every sample of a given substance have the same properties?
Because a substance has a fixed, uniform composition.
Explain why the composition of an element is fixed.
The composition of an element is fixed, because it contains only one type of atom.
Describe the composition of a compound.
The composition of a compound always contains two or more elements joined in a fixed proportion.
Why can the properties of a mixture vary?
The properties of a mixture can vary, because the composition of a mixture is not fixed.
On what basis can mixtures be classified as solutions, suspensions, or colloids?
Mixtures can be classified as solutions, suspensions, or colloids on the basis of the size of its largest particles.
What type of milk is a suspension?
What type of milk is a colloid?
What happens to the size of the drops of fat in milk when milk is homogenized?
They become smaller.
What property can be used to distinguish colloids and suspensions from solutions?
the scattering of light
Any characterestic of a material that can be observed or measured without changing the composition of the substances in the material
examples of physical properties
viscosity, conductivity, malleability, hardness, melting point, boiling point, and density
the resistance of a liquid to flowing
The greater the viscosity, the _____________ the liquid moves. (thick liquids---high viscosity/ thin liquids---low viscosity)
Viscosity of liquid decreases....becomes thinner, when....(ex.-motor oil---must be not get too thick in cold weather or too thin in hot weather)
A material's ablility to allow heat to flow...
example of materials with high conductivity and thus a good conductivity of electricity...
metals (wood is not)
The ability of a solid to be hammered without shattering...
Most __________ are malleable; ice is not, because it is brittle and shatters.
To compare the hardness of two materials is to see whick of the materials can __________ the other.
Hardest known material ...
The temperature at which a substance changes from a solid to liquid (ice to water)...
The temperature at which a substance changes from a liquid to a gas ....
Used to test the purity of a substance...
The ratio of the mass of a substance to its volume...
What is used to identify a material, to choose a material for a specific purpose, or to separate the substances in a mixture?
Steps to identify a material:
1.) Decide which properties to test.
2.) To do tests on a sample of the unknown.
3.) To compare the results with the data reported for known materials.
....crucial in solving crimes....
Two ways to separate mixtures:
A process that separates materials based on the size of their particles. Particles of the compounds that dissolve are small enough to pass through a strainer...
filtration (brewing coffee or tea)
A process that separates the substances in a solution based on their boiling points...
distillation (provide fresh water to a submarine)
A change that occurs when some of the properties of a material change, but the substances in the material remain the same...
physical change (water to ice/ water to steam/ ice to water)
Give examples of physical changes that can be reversed and physical changes that cannot be reversed....
Can be reversed: braiding hair; ice melts to water and then freezes again; removing wrinkles from a shirt/
Cannot be reversed: cutting hair; peeling a fruit or vegetable
Explain why sharpening a pencil is an example of a physical change.
Its size and shape change, but not its makeup (composition).
What allows a mixture to be separated by distillation?
How could you find out whether copper is harder or softer than the plastic used in a plastic cup?
See which of the materials can scratch the other.
Why would you expect the materials used to make pot holders to be poor conductors of heat?
So heat would not pass through them and burn your hand.
Silicon dioxide is a solid at room temperature and methanol is a liquid. Which substance has the higher melting point?
The solid always has the higher melting point.
When you describe a liquid as thick, are you saying it has a high or low viscosity?
Any ability to produce a change in the composition of matter....
Chemical properties can be observed only when the substances in a sample of matter are...
changing into different substances
Two examples of chemical properties:
A material's ability to burn in the presence of oxygen....
flammability (gasoline and paper are flammable/ some clothes are flame-resistant or will burn slowly)
The property that describes how readily a substance combines chemically with other substances....
reactivity (oxygen is highly reactive with most elements....will rust metal over time)
What occurs when a substance reacts and forms one or more new substances?
chemical change (cake batter turns into a cake; leaves on trees change color; food is digested in your stomach)
Three common types of evidence that a chemical change has occurred:
1.) A change in color (metal darkens over time)
2.) The production of a gas (mix vinegar with baking soda and carbon dioxide bubbles form)
3.) The formation of a precipitate (lemon juice added to milk makes it to turn a solid)
Any solid that forms and separates from a liquid mixture....
precipitate (acid to milk makes it curdle)
How do you tell if a substance of matter has undergone a chemical change?
The composition of matter will change into different substances. (If the composition or makeup of the material does not change, it is a physical change.)
Under what conditions can chemical properties be observed?
when it changes into different substances
A pat of butter melts and then burns in a hot frying pan. Which of these is a chemical change and which is a physical change?
the pat of butter melting is a physical change/ butter burning is a chemical change
If you spill bleach on jeans and that spot turns white, is this a chemical or physical change and why?
physical change, because the color changed, and despite the change in color no new material formed
Gold and platinum are used in jewelry making.
What does that tell you about their reactivity?
It has low reactivity because it does not react easily with the air or skin and will not easily turn colors.
Which of these substances is not an element....water, aluminum, hydrogen, or iron?
hydrogen (has only one atom).....water has hydrogen and oxygen atoms/ aluminum and iron have different types of atoms in them also
Is tap water an element, substance, compound, or mixture?
When a homemade oil-and-vinegar dressing is left standing, it separates into layers. Is the dressing a solution, suspension, colloid, or compound?
Which of the following is NOT an example of a physical change...density, flammability, hardness, or melting point?
flammability (chemical change)
Which is a poor conductor of heat...iron, silver, copper, or wood?
A material that can be hit without shattering....viscous, malleable, flammable, or hard?
At room temperature, a substance with a melting point of 40 degrees....solid, liquid, mixture, or gas?
has to be a solid (solid can melt)
Which action involves a chemical change...making ice cubes, adding sugar to tea, cutting wrapping paper, or baking a cake?
baking a cake (making ice--physical change/ adding sugar to tea----physical change (mixture)/ cutting wrapping paper---physical change (didn't change form)
A substance that has little tendancy to change into other substances is said to have low....reactivity, viscosity, density, or conductivity?
Formation of a precipitate is usually evidence of.....separation of a mixture, chemical change, formation of a mixture, or physical change?
Why do properties of a pure substance not vary from sample to sample?
Because it has a fixed, uniform composition.
What is the difference between an element or a compound?
Element cannot be broken down into simpler substances, but compound can be broken down because it is made of two or more substances.
What allows a mixture to be separated by filtration?
the size of its particles
Why is breaking down a compound into its elements considered a chemical change?
Because the compound changes from a substance of combined substances into two or more different substances.
All pure substances have a __________ composition.
Which property can be used to separate a mixture by distillation?
During which of these events does a chemical change occur....ice cubes melt, water boils, heated iron bar turns red, paper clip bends, or cake rises in the oven?
Cake rising in the oven
You can be CERTAIN that a chemical change occurs if...change cannot be reversed, new substances form, bubbles produced, precipitate forms, or color changes?
Certainty only when new substances form.
How many known elements are there?
Three states of matter:
solid, liquid, or gas
Explain the difference between solution, suspension, and colloid.
In a solution, substances dissolve and form a homogeneous mixture./In a suspension, a heterogeneous mixture separates into layers over time./ In a colloid, some particles are in between the size of the small and large particles.
Classification of matter?
Substance / Mixture
Element/ Compound Heterogeneous/Homo.
True of Compounds?
---always contains at least two elements
---its substances are always joined in a fixed proportion
---can be broken down into simpler substances
A ______________ mixture is difficult to distinguish the substances from one another.
The homogeneous mixture that forms when sugar is dissolved in a glass of hot water....
Example of a colloid
When matter undergoes a chemical change, the composition of the matter ______________.
When matter undergoes a physical change, the composition of the matter __________.
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