MATTER & CHEMICAL CHANGE Flashcards
What is chemistry?
the study of the properties of matter and the changes it undergoes
What is a caustic material
a material that burns or destroys living tissue
What are the five points of the Particle Model of Matter?
1) All matter is made up of extremely tiny particles.
2) Each pure substance has its own kind of particle, different from the
particles of other pure substances.
3) Particles attract each other.
4) Particles are always moving.
5) Particles at a higher temperature move faster on average than
particles at a lower temperature.
What is the difference between a “pure substance” and a “mixture”?
A pure substance contains its own unique kind of particle. Mixtures contain at least two kinds of particles.
What is the difference between a “homogenous mixture” and a “heterogeneous mixture”?
A homogeneous mixture is a mixture in which particles are uniformly scattered; has a uniform composition.
A heterogeneous mixture is a mixture in which the particles are not uniformly scattered; does not have a uniform composition.
*Tip: Easy to remember when you remember that “homo” meant “the same” and “hetero” means “different”
What is another name for a “homogeneous mixture” and how can you tell if a mixture is homogeneous?
Homogeneous mixtures are often called “solutions”.
When liquid, homogenous mixtures are often clear, cannot be filtered, and do not scatter light that passes through them.
What is another name for a “heterogenous mixture” and how can you tell if a mixture is heterogeneous?
Heterogenous mixtures are often called “mechanical mixtures”.
There are different types of heterogeneous mixtures, but in each there are discernible differences between the particles in the mixture.
Describe an “ordinary mechanical mixture” and give an example.
In an ordinary mechanical mixture, the different parts are big enough to see, and they stay mixed.
Example: granite
Describe a “suspension” and give an example.
*Hint: think about the different types of mixtures.
A suspension is a heterogeneous mixture made of large particles that
are uniformly mixed but will settle if left undisturbed.
Example: flour mixed in water
Describe a “colloid”, give an example, and explain how colloids are different than suspensions.
A colloid is a type of heterogeneous mixture composed of fine particles that are evenly distributed throughout a second substance.
Example: hair gel
Whether a mixture is a suspension or a colloid depends on the size of the particle, solubility and mixing ability.
Describe how an “emulsion” is different from from other colloids and give an example.
An emulsion is a colloid where a liquid is mixed in another liquid.
Example: mayonnaise
Emulsion will often separate into layers.
What is the “Law of Conservation of Mass”?
in a chemical change, the total mass of the new substances is always the same as the total mass of the original substances
Describe Dalton’s Atomic Theory.
*Hint: 5 points
Dalton’s Atomic Theory states that:
- All matter is made up of small particles called atoms
- Atoms cannot be created, destroyed, or divided into smaller particles
- All atoms of the same element are identical in mass and size
- Atoms of one element are different in mass and size from the atoms of other elements
- Compounds are created when atoms of different elements link together in definite proportions
What is the difference between electrons, neutrons and protons?
Electrons are negatively charged particles (outside of the nucleus).
Neutrons are uncharges particles in the atoms nucleus.
Protons are positively charged particles found inside the atom’s nucleus.
*Tip:
1) neutron - sounds like neutral, neutral means nothing
2) proton - has “pro” in the name and in a “pros vs. cons” list, the “pros” are the positives
3) electron - sounds like “electric” and being electrocuted would be a NEGATIVE experience
What is the difference between a physical change and a chemical change?
(provide an example of each)
A physical change is a change in form but not in chemical composition; no new substances are formed.
Example: liquid water freezing into ice
A chemical change is a a change in which one or more new chemical substances are formed
Example: mixing baking soda and vinegar produces C02 (that’s why it bubbles)
What does the “Law of Definite Composition” explain?
The Law of Definite Composition explains what makes compounds pure substances and says that:
“compounds are pure substances that contain two or more elements combined together in fixed (or definite) proportions”
Describe the difference between an element and a compound and give an example of each.
An element is a pure substance made of one type of particle that cannot be broken down into simpler substances by means of chemical change (ie. without breaking apart the atom).
Examples: carbon (C), hydrogen (H), chlorine (Cl), sodium (Na), and oxygen (O)
A compound is a pure substance that is made up of two or more elements chemically combined together; and can be broken down into elements again by chemical means (ie. through chemical reactions)
Examples: CO2 (carbon dioxide), H2O (water), and NaCl (table salt)
What is the definition of “Atomic Nucleus”?
the centre of the atom; contains the protons and neutrons
What is the difference between a chemical property and a physical property?
A chemical property is a characteristic of matter that describes how it reacts when undergoing a chemical change - these properties are determined through reactions with other substances (like air, or acid)
Whereas a physical property is a characteristic of matter that is not associated with changes in its chemical composition - we can identify physical properties of matter through our senses and through measurement (like length, density)
List some chemical properties of matter.
Corrosiveness, combustibility, toxicity, oxidation states, chemical stability (radioactive?), flammability, coordination number, reactivity, possible chemical bonds
List some physical properties of matter.
Colour, odour, texture, lustre (is it shiny), taste, temperature (boiling/freezing points), hardness, volume, mass, size, weight, length
What is the difference between atomic mass and atomic number and how are they related?
Atomic mass is the average mass of an atom of an element.
Atomic number describes the number of protons in the nucleus of an atom
The atomic number is one part of the atomic mass, as the atomic number refers to the number of protons in the nucleus of an atom while the atomic mass is the sum of the number of protons and the number of neutrons within the nucleus.
What are element symbols?
one or more letters used to represent the name of a substance (e.g., O is the symbol for oxygen)
*Note: element symbols may contain more than one letter, for example Ca is the element symbol for calcium. It is important to remember that element symbols start with a capital letter. So, in the compound NaCl, the “Na” is one element (sodium), and the “Cl” is another element (chlorine)
What are 7 signs that a chemical change has occurred?
- Heat is produced or absorbed (ie. it got hotter or colder)
- The starting material is used up
- There is a change in colour
- A material with new properties forms
- Gas bubbles form in a liquid
- A precipitate forms in a liquid.
- The change is difficult to reverse
*Note: generally you would want to note that two or more of these observations is present before confirming a chemical reaction has taken place
What is the difference between a “qualitative property” and a “quantitative property”?
Qualitative describes a property that can be described, but not necessarily measured ( like colour, or smell).
On the other hand, quantitative properties can be measured (like conductivity, density and solubility)
How can we describe matter?
matter is anything that has MASS and VOLUME
If a particle gains energy (for example it is heated up), does it increase or decrease in speed?
increase
If a particle speeds up, is it more or less attracted to other particles?
less
(think if we speed up particles we make matter act more like a gas, and if in gases particles are far apart)
If particles are less attracted to each other are they closer together or further apart?
further apart
(think about gases, these particles move quickly, aren’t bound together like solids, so they are further apart)
What is kinetic energy?
the energy of motion
What has more kinetic energy gases or solids
gases have more, they have high kinetic energy (these particles move around) and solids have less, they have low kinetic energy (these particles don’t really move much)
What is the difference between a mixture and a compound?
Compounds are pure substances that contain different elements which are chemically bonded together (creating a single particle)
Example: NaCl or salt (two chemically bonded elements)
Mixtures are not pure substances, and contain two or more different particles
Example: salt water (mixture of NaCl and H2O)
